Crystallization and Determination of Melting and Boiling Points
Crystallization and Determination of Melting and Boiling Points
Crystallization and Determination of Melting and Boiling Points
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Experiment<br />
1<br />
<strong>Crystallization</strong> <strong>and</strong> <strong>Determination</strong> <strong>of</strong> <strong>Melting</strong> <strong>and</strong><br />
<strong>Boiling</strong> <strong>Points</strong><br />
by Anawat Ajavakom<br />
Objectives<br />
1) To perform a purification <strong>of</strong> organic compounds by crystallization.<br />
2) To determine melting point <strong>and</strong> boiling point <strong>of</strong> unknown compounds.<br />
3) To become familiar with general apparatus in organic chemistry laboratory.<br />
Principles<br />
1. <strong>Crystallization</strong><br />
Solid organic compounds are usually purified by crystallization. This general<br />
technique involves dissolving the impure material in a minimum amount <strong>of</strong> hot solvent<br />
<strong>and</strong> cooling the solution slowly. The dissolved material has lower solubility at lower<br />
temperature <strong>and</strong> a solid material will form as the solution is cooled down. This process is<br />
called either ‘crystallization’ if the crystal growth is relatively slow <strong>and</strong> selective or<br />
‘precipitation’ if the process is rapid <strong>and</strong> yields smaller crystals.<br />
In microscale organic laboratory, there are two common methods for crystallization;<br />
1) Semi-microscale crystallization (for solid material <strong>of</strong> more than 0.1 g).<br />
2) Microscale crystallization (for solid material <strong>of</strong> less than 0.1 g)<br />
In this experiment, you will perform a semi-microscale crystallization using 0.5 g <strong>of</strong><br />
solid unknowns, which could be either benzoin or benzoic acid.<br />
O<br />
COOH<br />
OH<br />
Benzoin<br />
Benzoic acid<br />
Four main steps in semi-microscale crystallization are;<br />
1) Dissolving the solid<br />
2) Removing insoluble impurities (if necessary)<br />
3) <strong>Crystallization</strong><br />
4) Isolation <strong>of</strong> crystals<br />
2. <strong>Melting</strong> <strong>Points</strong> <strong>and</strong> <strong>Boiling</strong> <strong>Points</strong><br />
Physical properties that are useful for distinguishing compounds include color,<br />
melting point, boiling point, density, <strong>and</strong> reflective index. In this experiment, we will learn<br />
how to determine melting <strong>and</strong> boiling points.<br />
- 1 -
<strong>Melting</strong> <strong>Points</strong><br />
The melting point is used by organic chemists not only to identify compounds, but<br />
also to verify their purity. To measure the melting point, a small amount <strong>of</strong> sample is<br />
heated in an apparatus equipped with a thermometer while two temperatures are noted.<br />
The first is the point at which the first drop <strong>of</strong> liquid forms among the crystals; <strong>and</strong> the<br />
other is the point at which the whole mass <strong>of</strong> crystals turns to a clear liquid. The melting<br />
point is recorded as a range <strong>of</strong> temperatures, for example 180-182 °C. Pure compounds<br />
usually have narrow melting temperature ranges (within 1-2 degree).<br />
<strong>Melting</strong> point can be used as supporting evidence in identifying a compound as well.<br />
Not only can we compare melting points <strong>of</strong> two individual compounds, a procedure called<br />
‘mixed melting point’ may be used with the same compound taken from different<br />
sources. Since melting point is a unique physical property, the mixture <strong>of</strong> two samples<br />
would have a narrow melting range if the mixture composes <strong>of</strong> just one compound. On<br />
the other h<strong>and</strong>, the observed melting ranges would be broad if the mixture composes <strong>of</strong><br />
two different compounds.<br />
<strong>Boiling</strong> <strong>Points</strong><br />
When a liquid is heated, its vapor pressure increases until it equals the atmospheric<br />
pressure. And at this temperature, the liquid starts to boil. The normal boiling point is<br />
measured at 760 mmHg or 1 atm. However at lower pressures, the vapor pressure<br />
needed for boiling is also lower, <strong>and</strong> so the liquid boils at lower temperature. (Look at the<br />
reference, fig 6-8 p.606.)<br />
Experimental Procedure<br />
Part A<br />
1) Obtain a sample from your instructor. Record sample number.<br />
2) Keep 10 mg (or about 2 grains <strong>of</strong> rice) in a watch glass for melting point<br />
determination <strong>and</strong> place the same amount in each <strong>of</strong> two test tubes.<br />
3) Add 10 drops <strong>of</strong> ethanol in one test tube, <strong>and</strong> 10 drops <strong>of</strong> water in another.<br />
4) Gently shake both test tubes <strong>and</strong> observe the solubility at room temperature.<br />
a) If the sample completely dissolves in just one tube, your solvent for crystallization<br />
is the one that cannot dissolve your sample at room temperature.<br />
b) If the sample does not dissolve in both tubes, place the tubes in a steam bath for<br />
30 seconds <strong>and</strong> observe the solubility. Your solvent for crystallization is the one<br />
that can dissolve your sample at high temperature.<br />
c) Report the solvent <strong>of</strong> choice before proceeding to the next step.<br />
5) Place the rest <strong>of</strong> your sample in a 50 mL Erlenmeyer flask, follow by 5 mL <strong>of</strong> your<br />
solvent.<br />
6) Heat the mixture on a hotplate <strong>and</strong> swirl occasionally. Do not allow the mixture to<br />
boil vigorously. If sample doesn’t completely dissolve when the solvent starts to boil,<br />
add a small amount <strong>of</strong> solvent until a clear solution is obtained. However, impurities<br />
or some black particles may still exist.<br />
- 2 -
7) Setup a hot filtration kit as shown in the picture below. Filter paper is available in the<br />
supply room. Consult your instructor on how to transfer <strong>and</strong> filter a hot solution.<br />
Glass funnel<br />
with filter paper<br />
Empty<br />
flask<br />
Solution to be<br />
filtered<br />
Figure 1<br />
8) When the hot filtration is finished, remove the flask from the hot plate <strong>and</strong> set aside.<br />
Wait for the crystals to grow <strong>and</strong> do not move the flask around. You may measure<br />
the melting point <strong>of</strong> unpurified sample while waiting (see step 10).<br />
9) Vacuum filter <strong>and</strong> dry the crystals by placing them on a watch glass heated on a<br />
steam bath. Use a glass rod to gently turn the crystals, ensuring thorough drying.<br />
10) Put the unpurified sample into a capillary tube (about 4-5 mm in height). Attach the<br />
tube to a thermometer with sewing thread <strong>and</strong> set the apparatus as in Figure 2.<br />
Clamp<br />
Thermometer<br />
50 mL Beaker<br />
Paraffin Oil<br />
Sewing thread<br />
Sample in<br />
capillary tube<br />
Hotplate<br />
Figure 2<br />
- 3 -
11) Turn on the hotplate <strong>and</strong> observe the melting point. Use a clean glass rod to stir the<br />
paraffin oil to ensure a uniform heat distribution.<br />
12) Record the temperatures<br />
a) when the sample starts to melt.<br />
b) when the melting process is finished.<br />
13) Allow the paraffin oil to cool down <strong>and</strong> repeat step 10) to12) with the purified sample.<br />
Part B<br />
1) Obtain an unknown liquid sample from your instructor. Record the sample number.<br />
2) Attach a clean <strong>and</strong> empty test tube to a thermometer with sewing thread. Put an<br />
empty capillary tube in the test tube so that the open end <strong>of</strong> capillary is down. Set up<br />
the apparatus as in Figure 3.<br />
Test tube<br />
Clamp<br />
Thermometer<br />
Capillary<br />
Close end<br />
50 mL Beaker<br />
Capillary tube<br />
Capillary<br />
tube<br />
Paraffin Oil<br />
Sewing thread<br />
Capillary<br />
Open end<br />
Hotplate<br />
Sample in<br />
test tube<br />
Figure 3<br />
3) Ensure that the paraffin oil is not hot <strong>and</strong> place 2-3 mL <strong>of</strong> sample in the test tube.<br />
4) Turn on the hot plate <strong>and</strong> use a clean glass rod to stir the paraffin oil to ensure a<br />
uniform heat distribution.<br />
5) Record the temperatures when rapid air bubbles come out from the capillary<br />
6) Turn <strong>of</strong>f the hot plate <strong>and</strong> carefully insert a ceramic tile between the beaker <strong>and</strong> the<br />
hotplate.<br />
7) As the temperature decreases, air bubbling will gradually slow down. Record the<br />
temperature when you see the last bubble comes out <strong>and</strong> the liquid goes into the<br />
capillary tube<br />
8) Report the boiling point to your instructor. If a repetition is needed, allow the paraffin<br />
oil to cool, then replace the capillary tube with a new one. Add more liquid sample if<br />
necessary <strong>and</strong> repeat step 4) to 7).<br />
- 4 -
Safety Precautions<br />
Wear safety goggles <strong>and</strong> lab coat at all times.<br />
Reference<br />
D. L. Pavia, G. M. Lampman, G. S. Kriz, R. G. Engel, Introduction to Organic Laboratory<br />
Techniques, A Microscale Approach, Part 5, 577-616.<br />
- 5 -
Experiment<br />
2<br />
Extraction <strong>and</strong> Simple Distillation<br />
by Anawat Ajavakom<br />
Objectives<br />
1) To separate neutral, acidic, <strong>and</strong> basic compounds in a mixture by extraction.<br />
2) To become familiar with separatory funnel <strong>and</strong> other general apparatus in organic<br />
chemistry laboratory.<br />
3) To perform a simple distillation <strong>of</strong> organic compounds.<br />
Principles<br />
To isolate pure components from a mixture, many practical techniques can be<br />
chosen depending on the difference in physical <strong>and</strong> chemical properties. Extraction is a<br />
very simple way for isolation. It can be used with mixtures containing neutral, acidic, <strong>and</strong><br />
basic compounds, for example, the isolation <strong>of</strong> benzoin (a neutral component) <strong>and</strong><br />
benzoic acid (an acidic component) from a mixture given to you in this experiment.<br />
O<br />
COOH<br />
OH<br />
Benzoin<br />
Benzoic acid<br />
Both benzoin <strong>and</strong> benzoic acid are white solid substances which can dissolve in<br />
dichloromethane (CH 2 Cl 2 ). With the difference in acidity, these two compounds can be<br />
separated by acid-base extraction method as outlined in the flow chart.<br />
Mixture <strong>of</strong> benzoin <strong>and</strong> benzoic acid<br />
dissolved in CH 2 Cl 2<br />
Shake with diluted NaOH<br />
Organic layer<br />
Benzoin<br />
in CH 2 Cl 2<br />
Benzoin<br />
Dry <strong>and</strong> evaporate<br />
CH 2 Cl 2<br />
Aqueous layer<br />
Sodium benzoate<br />
in water<br />
White Precipitate<br />
Add cold conc. HCl<br />
Filter<br />
Benzoic acid<br />
- 6 -
Acidic compounds (HA) react with bases (OH - ) to give their conjugated bases (A - )<br />
<strong>and</strong> water, as described in equation (i).<br />
HA + OH - A - + H 2 O<br />
(i)<br />
Experimental Procedure<br />
Part A<br />
1) Obtain a mixture from your instructor. This mixture consists <strong>of</strong> approximately equal<br />
weights <strong>of</strong> benzoin (neutral) <strong>and</strong> benzoic acid (acidic).<br />
2) Weigh 1g <strong>of</strong> the mixture <strong>and</strong> dissolve with 20 mL <strong>of</strong> CH 2 Cl 2 in a 50-mL separatory<br />
funnel. Swirl until solid dissolves completely.<br />
3) Add 8 mL <strong>of</strong> 10% NaOH into the separatory funnel. Shake the funnel carefully for 10<br />
seconds as demonstrated by your instructor. (*Remember to hold the separatory<br />
funnel with both h<strong>and</strong>s <strong>and</strong> to vent it frequently with the lower end pointed upward<br />
<strong>and</strong> away from other people.) Settle for a few minutes <strong>and</strong> split the layers into two<br />
separate flasks.<br />
4) Transfer the organic layer into the separatory funnel. Add a new portion <strong>of</strong> 8 mL <strong>of</strong><br />
10% NaOH into the separatory funnel. Shake, settle, <strong>and</strong> split the layers. Transfer<br />
the lower organic layer in a flask <strong>and</strong> keep the upper aqueous layer in the funnel.<br />
5) Combine the first aqueous portion with the solution in the funnel. Add 15-mL <strong>of</strong><br />
CH 2 Cl 2 . Shake, settle, <strong>and</strong> split the layers. Combine the CH 2 Cl 2 layers with that from<br />
step 4). Transfer the aqueous layers into another flask for experiment in Part B.<br />
6) Wash the organic solution by shaking with 10 mL <strong>of</strong> water. Discard the aqueous<br />
layer. Dry the organic layer over anhydrous sodium sulfate (Na 2 SO 4 ) (roughly about<br />
2-3 tea spoons). After st<strong>and</strong>ing for a few minutes, this organic solution should be<br />
clear. If not, consult your instructor.<br />
7) Gravity filter the CH 2 Cl 2 solution into a 50-mL round bottom flask <strong>and</strong> evaporate the<br />
solvent by distillation. The distillation set should be prepared as shown in Figure 1<br />
(Don’t forget to place a lab jack underneath the hot plate so that the heating source<br />
can be instantly removed in case <strong>of</strong> EMERGENCY.) Consult your instructor before<br />
heating the distillation set.<br />
8) Observe the temperature <strong>of</strong> the distillate (solvent) <strong>and</strong> collect in a conical flask.<br />
9) Remove the heating source when the content remaining in the flask is about 2-3 mL.<br />
Allow the solvent to evaporate while the flask is cooling to room temperature.<br />
10) Collect <strong>and</strong> weigh the solid residue <strong>of</strong> benzoin.<br />
- 7 -
Thermometer<br />
Thermometer<br />
Adapter<br />
Water out<br />
50 mL Round<br />
Bottom Flask<br />
Condenser<br />
Parafin Oil<br />
<strong>Boiling</strong> Stone or<br />
Ceramic Pieces<br />
Oil Bath<br />
Water in<br />
Hot Plate<br />
Conical Flask<br />
Part B<br />
Figure 1<br />
1) Acidify the combined aqueous portions from Part A step 5) by slowly add 6M HCl<br />
until the solution is acidic to litmus paper.<br />
2) Cool the resulting suspension in ice bath for a few minutes.<br />
3) Vacuum filter <strong>and</strong> air dry the benzoic acid for a few minutes.<br />
4) Collect <strong>and</strong> weigh the solid benzoic acid.<br />
Safety Precautions<br />
Concentrated HCl is highly corrosive. Safety goggles <strong>and</strong> lab coat must be worn at all<br />
times.<br />
Reference<br />
D. L. Pavia, G. M. Lampman, G. S. Kriz, R. G. Engel, Introduction to Organic Laboratory<br />
Techniques, A Microscale Approach, Part 5, 617-650.<br />
- 8 -
Experiment<br />
3<br />
Thin Layer <strong>and</strong> Column Chromatography<br />
by Pattara Sawasdee<br />
Objectives<br />
1) To perform separation techniques <strong>of</strong> column chromatography.<br />
2) To analyze the purity <strong>of</strong> the isolated compounds using TLC technique.<br />
Principles<br />
Chromatography is a laboratory method based on selective adsorption by which<br />
components in complex mixtures can be separated for identification or purification<br />
purposes. (Adsorption is the binding <strong>of</strong> molecules to the surface <strong>of</strong> another substance.)<br />
The utilization <strong>of</strong> a moving (or mobile) phase <strong>and</strong> a stationary phase is common to all<br />
chromatographic separation techniques. A mixture <strong>of</strong> compounds is introduced into the<br />
chromatographic system as a narrow zone <strong>and</strong> is partly retained by the stationary phase<br />
while the mobile phase carries the components through the system. Each component in<br />
the mixture will be distributed between the mobile phase <strong>and</strong> the stationary phase, but not<br />
to the same extent. Components that are more loosely interacted by the stationary phase<br />
will be swept through the column more rapidly, <strong>and</strong> a separation will be achieved.<br />
When the stationary phase is packed inside a column, the experimental<br />
procedure is called column chromatography. When the stationary phase is planar (e.g.,<br />
a piece <strong>of</strong> filter paper or a coated glass), the mobile phase is usually liquid <strong>and</strong> the<br />
techniques are classified according to the stationary phase which is paper or thin-layer<br />
chromatography.<br />
Chromatography is a sophisticated separation method. Its versatility results from<br />
many adjustable factors which include:<br />
1. Types <strong>of</strong> adsorbent<br />
2. Types <strong>of</strong> solvent, which relates to the polarity <strong>of</strong> the mobile phase<br />
3. Column size, both length <strong>and</strong> diameter, relative to the amount <strong>of</strong> mixtures<br />
4. Rate <strong>of</strong> elution or solvent flow<br />
In this experiment, you will use an open column chromatography to separate a<br />
mixture <strong>of</strong> two compounds (benzil <strong>and</strong> benzoin). But first, you will have to determine a<br />
suitable solvent system using thin-layer chromatography (TLC). The ideal solvent system<br />
is the one that allows the faster-moving component to have an R f value <strong>of</strong> about 0.25-<br />
- 9 -
0.35 on the TLC plate while giving a good separation between the two spots (maximum<br />
R f difference). When you know the best solvent system, use this solvent as the eluent<br />
(mobile phase) for the column chromatography. After the separation <strong>of</strong> the two<br />
compounds, you will identify them by comparing the R f with that <strong>of</strong> the authentic<br />
compounds.<br />
***<br />
R f st<strong>and</strong>s for ratio <strong>of</strong> fronts or rate <strong>of</strong> flow***<br />
Experimental Procedure<br />
Part A: Mobile phase determination by TLC method<br />
1) Obtain four TLC plates from the supply room. By using a pencil, not pen, lightly<br />
draw a line across the short side <strong>of</strong> each plate, on the silica gel side approximately 1<br />
cm from the bottom. Be careful not to scratch the silica gel as you are drawing the<br />
line.<br />
2) Use small capillary tubes to spot solutions <strong>of</strong> benzil <strong>and</strong> benzoin along the line. Keep<br />
a gap (0.8-1 cm) between the two spots. When spotting the solutions, gently <strong>and</strong><br />
quickly touch the capillary to the surface <strong>of</strong> the plate so that the spots are not too<br />
large. Also, write a letter above or below to indicate what is spotted at each position<br />
(e.g. “A” for benzil <strong>and</strong> “B” for benzoin) as shown in Figure 1.<br />
A<br />
B<br />
Watch glass<br />
Beaker<br />
1 cm<br />
1 cm<br />
A = benzil solution<br />
B = benzoin solution<br />
Fig 1. TLC plate<br />
A B<br />
• •<br />
Filter paper<br />
TLC plate<br />
Solvent level below the<br />
pencil line on TLC plate<br />
Fig 2. TLC chamber<br />
- 10 -
3) Set up a TLC chamber as shown in Figure 2. Put a piece <strong>of</strong> filter paper in a 100 mL<br />
beaker. Place a small amount <strong>of</strong> n-hexane in this beaker. The liquid should cover the<br />
bottom <strong>of</strong> the beaker but the surface should be below the pencil line when the plate<br />
is placed in the beaker (that is, less than 1 cm in depth). The filter paper lining is<br />
used to saturate the atmosphere within the beaker with solvent fumes.<br />
4) Place one spotted TLC plate in the TLC chamber, cover with a watch glass <strong>and</strong><br />
allow the solvent to move through the plate until it is approximately 0.5-1 cm from<br />
the top. Do not disturb the chamber while the plate is being developed!!!<br />
5) Remove the plate from the chamber <strong>and</strong> mark the solvent front with a pencil. Allow<br />
the plate to dry for a few minutes. Place it under short-wave ultraviolet light (254 nm)<br />
<strong>and</strong> circle dark spots appear on the plate under the UV light.<br />
6) Repeat step 2) to 5) for other three TLC plates but each time change the mobile<br />
phase from pure n-hexane to a mixture <strong>of</strong> ethyl acetate <strong>and</strong> n-hexane; 1:1, 1:2 <strong>and</strong><br />
1:4, respectively.<br />
7) From the results, decide which solvent system would be appropriate for the<br />
separation <strong>of</strong> benzil <strong>and</strong> benzoin (PART B). Report the result to your instructor.<br />
PART B: Separation <strong>of</strong> a mixture by column chromatography<br />
1) Prepare a silica gel column as shown in Fig 3, first plugging the column with cotton<br />
<strong>and</strong> then affix to a clamp st<strong>and</strong>. Place a beaker under the outlet tap.<br />
Funnel<br />
Cotton<br />
Fig 3. Setting up a<br />
Chromatographic column<br />
Beaker<br />
2) In a clean <strong>and</strong> dry beaker, mix silica gel (~6 g) with your solvent <strong>of</strong> choice from<br />
PART A (~30 mL) (CAUTION: Silica gel dust is very harmful if inhaled). Then, slowly<br />
- 11 -
transfer the slurry into the column using a glass funnel until the silica gel level is<br />
about 10-12 cm (when settle). If necessary, gently tap the side <strong>of</strong> the column with a<br />
rubber tube during the packing process to compact the silica gel.<br />
3) Open the stopcock to allow liquid to drain into the beaker. Adjust the level <strong>of</strong> liquid<br />
around 2-3 cm above the level <strong>of</strong> silica gel <strong>and</strong> close the stopcock.<br />
4) Obtain 0.1 g <strong>of</strong> solid mixture (benzil+benzoin) from your instructor. Place it in a test<br />
tube <strong>and</strong> dissolve with a minimum amount <strong>of</strong> dichloromethane (~1-1.5 mL).<br />
5) Open the stopcock <strong>and</strong> drain the solvent in the column until it reaches the silica gel<br />
surface, <strong>and</strong> then close the stopcock. Slowly add the mixture solution into the<br />
column via a pipette. The flat surface <strong>of</strong> silica gel should be minimally disturbed.<br />
6) Open the stopcock to allow sample adsorption onto the silica gel, <strong>and</strong> then close the<br />
stopcock.<br />
7) Rinse the inside wall <strong>of</strong> the column with 1-2 mL <strong>of</strong> solvent.<br />
8) When the solvent reaches the top <strong>of</strong> the silica gel surface, carefully add 25 mL (or as<br />
much as your column can contain) <strong>of</strong> solvent for eluting. It is very important that the<br />
column never be dried out during the eluting process.<br />
9) Collect 10 fractions (2 mL each) in test tubes <strong>and</strong> label as 1, 2, 3,…..<br />
10) Analyze all <strong>of</strong> your collected fractions by TLC (Fig 4).<br />
1234<br />
Fig 4. TLC plate for<br />
checking each fraction<br />
5mm<br />
1cm<br />
11) Combine the fractions containing pure benzoin in a ceramic evaporating dish <strong>and</strong><br />
place the dish on a steam bath until a solid or thick oil is obtained.<br />
12) Allow the dish to cool to room temperature <strong>and</strong> collect the solid into a pre-weighed<br />
plastic bag.<br />
13) Calculate the weight <strong>of</strong> isolated benzoin.<br />
14) Calculate recovery percentage.<br />
15) Repeat step 11) to 14) with fractions containing pure benzil.<br />
- 12 -
Safety Precautions<br />
a. Wear safety goggles <strong>and</strong> lab coat at ALL times.<br />
b. n-hexane <strong>and</strong> ethyl acetate are flammable. Never use them near open flame or<br />
hot plate.<br />
c. Cover all vessels containing silica dust. It is dangerous if inhaled.<br />
Waste Disposal<br />
Place all organic solvents <strong>and</strong> chemicals into container marked “Organic Waste”.<br />
Reference<br />
1) D. L. Pavia, G. M. Lampman, G. S. Kriz, R. G. Engel, Introduction to Organic<br />
Laboratory Techniques, 3 rd edition, Part 2: technique 10 column chromatography<br />
<strong>and</strong> technique 11 thin-layer chromatography, pp.593-629.<br />
- 13 -
Experiment<br />
4<br />
Preparation <strong>of</strong> Cyclohexene from Cyclohexanol<br />
by Pattara Sawasdee<br />
Objectives<br />
1) To synthesize cyclohexene from cyclohexanol via dehydration reaction <strong>of</strong> an alcohol.<br />
2) To classify alkanes <strong>and</strong> alkenes using chemical reaction test<br />
Principles<br />
In this experiment some important properties <strong>of</strong> hydrocarbons will be studied. You’ll<br />
perform tests which to distinguishing between saturated hydrocarbons (alkanes) <strong>and</strong><br />
unsaturated hydrocarbons (alkenes). An alkene (cyclohexene) will be prepared by<br />
dehydration <strong>of</strong> an alcohol (cyclohexanol).<br />
Alcohol dehydration is an acid-catalyzed elimination reaction, which can be<br />
performed by strong, concentrated mineral acids such as phosphoric acid.<br />
OH<br />
H 3 PO 4<br />
+ H 2 O<br />
cyclohexanol<br />
b.p. 161 o C<br />
cyclohexene<br />
b.p. 83 o C<br />
In the reaction above, cyclohexene is the only alkene that can be formed under<br />
these conditions. Cyclohexene <strong>and</strong> water are removed via azeotropic distillation to drive<br />
the equilibrium to product (Le Chatelier’s Principle). Traces <strong>of</strong> acid in the crude product<br />
are removed by treatment with sodium carbonate solution. A final wash with water<br />
removes any remaining carbonate.<br />
Cyclohexene is an unsaturated hydrocarbon. In chemistry, a hydrocarbon is any<br />
chemical compound that consists only <strong>of</strong> the elements carbon (C) <strong>and</strong> hydrogen (H). The<br />
major classes <strong>of</strong> hydrocarbons are alkanes, alkenes, alkynes <strong>and</strong> aromatic hydrocarbons.<br />
The alkanes are the least reactive class, because they contain only carbon <strong>and</strong> hydrogen<br />
<strong>and</strong> they have no reactive functional groups. There are a number <strong>of</strong> useful chemical tests<br />
that can differentiate alkanes from alkenes. These tests are based upon the reactivity <strong>of</strong><br />
alkenes with a variety <strong>of</strong> reagents to which the alkanes are insensitive. In this experiment,<br />
you will distinguish cyclohexene (alkene) from cyclohexane (alkane) using bromine <strong>and</strong><br />
permanganate tests.<br />
- 14 -
1) Bromine test using bromine in chlor<strong>of</strong>orm (Br 2 /CHCl 3 )<br />
R C C<br />
H H<br />
R<br />
Br H<br />
+ Br 2 R C C R<br />
H Br<br />
A solutions <strong>of</strong> bromine in CHCl 3 has an intense red-orange color. When Br 2 in<br />
CHCl 3 is mixed with an alkane, no change is initially observed. When it is mixed with<br />
an alkene or alkyne, the color <strong>of</strong> Br 2 rapidly disappears as an addition reaction takes<br />
place.<br />
2) Permanganate Test (Baeyer’s test)<br />
OH OH<br />
3 R C C R + 2KMnO 4 + 4H 2 O 3 R C C R + 2MnO 2 + 2KOH<br />
H H<br />
H H<br />
The disappearance <strong>of</strong> the purple color <strong>of</strong> potassium permanganate <strong>and</strong> the<br />
formation <strong>of</strong> brown precipitate (MnO 2 ) is a positive test. The alkenes are readily<br />
oxidized by potassium permanganate to form diols. The alkanes are not reacted with<br />
the potassium permanganate as the purple color remains.<br />
Experimental Procedure<br />
Part A: Preparation <strong>of</strong> cyclohexene by dehydration <strong>of</strong> cyclohexanol<br />
OH<br />
H3 PO 4<br />
heat<br />
1) Transfer 10 mL (9.4 g.) <strong>of</strong> cyclohexanol to a 100 mL round-bottomed flask. Add 5 mL<br />
<strong>of</strong> 85% H 3 PO 4 . Thoroughly mix the solution by swirling.<br />
CAUTION: Phosphoric acid is strongly corrosive. If it is in contact with your skin,<br />
rinse with tap water immediately <strong>and</strong> report the incident to your instructor.)<br />
2) Add a few pieces <strong>of</strong> boiling chips, <strong>and</strong> assemble the flask for fractional distillation<br />
(Figure 1) using a 25 mL graduated cylinder in an ice-water bath as a receiver.<br />
(cyclohexene is very volatile <strong>and</strong> it will evaporate quite rapidly)<br />
3) Start circulating the cooling water in the condenser <strong>and</strong> heat the reaction flask using<br />
a heating mantle (avoid overheating). The temperature <strong>of</strong> the distilling vapor should<br />
be regulated so that it does not exceed 100°C.<br />
- 15 -
4) When white fumes appear in the round bottom flask, <strong>and</strong> a few milliliters <strong>of</strong> liquid<br />
remains in the reaction flask, discontinue the distillation by turning <strong>of</strong>f the heating<br />
mantle.<br />
5) Transfer the distillate* to a small separatory funnel <strong>and</strong> add about 10 mL <strong>of</strong> 10%<br />
aqueous Na 2 CO 3 . Swirl the solution slowly at first <strong>and</strong> then shake vigorously to<br />
neutralize the solution. Vent frequently to prevent CO 2 pressure build up.<br />
6) Allow the layers to separate, drain <strong>and</strong> test the pH <strong>of</strong> the aqueous layer (bottom<br />
layer). Repeat the neutralization until the aqueous layer is basic to litmus. The<br />
aqueous layer can then be discarded.<br />
7) Wash the organic layer with 10 mL <strong>of</strong> water.<br />
8) Transfer the organic layer to a dried 50 mL Erlenmeyer flask. Add anhydrous<br />
Na 2 SO 4 to the flask <strong>and</strong> swirl occasionally until the solution is dry <strong>and</strong> clear.<br />
9) Weigh the cyclohexene product <strong>and</strong> calculate the total yield.<br />
* distillate = Lliquid condensed from vapor in distillation<br />
distill<strong>and</strong> = The material in the distillation apparatus that is to be distilled.<br />
Thermometer<br />
Water out<br />
Water in<br />
Fractionating<br />
column<br />
Condensor<br />
Graduate cylinder<br />
ice-water bath<br />
Heating mental<br />
Figure 1: a fractional distillation apparatus<br />
Part B: Test <strong>of</strong> unsaturation<br />
Samples : 1. Cyclohexane (Alkanes): from the laboratory<br />
2. Cyclohexene (Alkenes): from your synthesis (Part A)<br />
1) Bromine test: Place 3 drops <strong>of</strong> samples in dry test tubes. Then, add about 3-4<br />
drops <strong>of</strong> a bromine solution in chlor<strong>of</strong>orm. Stopper each tube, shake, <strong>and</strong> record<br />
the observation. If decolorization occurs, test for hydrogen bromide with wet<br />
litmus.<br />
- 16 -
2) Permanganate test: Place 3 drops <strong>of</strong> samples in clean test tubes. Add 3-4<br />
drops <strong>of</strong> 0.1% permanganate solution drop by drop while shaking. Watch for<br />
disappearance <strong>of</strong> the purple color <strong>and</strong> formation <strong>of</strong> a brown precipitate within 1<br />
minute.<br />
Safety Precautions<br />
- Phosphoric acid is a strong acid capable <strong>of</strong> producing severe burns to skin or eyes.<br />
- Cyclohexanol can be irritating to the respiratory system <strong>and</strong> skin.<br />
- Cyclohexene is not particularly dangerous but is highly flammable <strong>and</strong> has an<br />
unpleasant smell.<br />
- Bromine is highly volatile, toxic, <strong>and</strong> causes severe skin burns.<br />
Waste Disposal<br />
All contents <strong>of</strong> your test tubes from bromine test reactions go into “HALOGENATED<br />
organic waste”.<br />
Quiz<br />
Quiz will cover this material <strong>and</strong> the basic knowledge <strong>of</strong> hydrocarbons.<br />
- 17 -
Experiment<br />
5<br />
Alkyl Halides<br />
by Paitoon Rashatasakhon<br />
Objectives<br />
1) To classify alkyl halides according to their structures <strong>and</strong> reactivity.<br />
2) To underst<strong>and</strong> the relationship between structures <strong>and</strong> reactivity <strong>of</strong> alkyl halides.<br />
3) To distinguish the differences in S N 1 <strong>and</strong> S N 2 reactions.<br />
Principles<br />
Alkyl halides are hydrocarbon compounds containing at least one atom <strong>of</strong><br />
halogen directly bonded to an alkyl group. With a general formula R-X, the halogen<br />
atom could be F, Cl, Br, or I. If the halogen atom is attached to an aromatic ring, the<br />
compound will be referred to as an aryl halide. In terms <strong>of</strong> reactivity, aryl halides are<br />
usually less reactive than alkyl halides.<br />
Most <strong>of</strong> the reactions for alkyl halides are Nucleophilic Substitution reaction.<br />
Nucleophiles are molecules with high electron density or lone pairs <strong>of</strong> electrons, or<br />
ions with a negative charge. They can form bond by donating electrons to another<br />
molecule having a position <strong>of</strong> lower electron density (electrophiles). Examples <strong>of</strong><br />
nucleophilic species are: water, amines, ammonia, cyanide ion, alkoxide ions, <strong>and</strong><br />
hydroxide ion.<br />
Alkyl halides can react with a number <strong>of</strong> nucleophilic reagents, both organic <strong>and</strong><br />
inorganic species. Therefore, alkyl halides are usually good starting materials in the<br />
synthesis <strong>of</strong> compounds with other functional groups.<br />
The reaction may occur by one <strong>of</strong> two mechanisms designated S N<br />
1 or S N<br />
2.<br />
Which mechanism operates depends on the structure <strong>of</strong> the R group, nucleophile, <strong>and</strong><br />
the reaction conditions.<br />
General form <strong>of</strong> the S N 1 mechanism<br />
nuc: = nucleophile<br />
X = leaving group (usually halide)<br />
This mechanism involves the formation <strong>of</strong> a carbocation as the crucial<br />
intermediate in the rate-determining step. The reaction exhibits unimolecular (or "firstorder")<br />
kinetics, because only one molecule is involved in the rate-determining step.<br />
Since the mechanism goes through a carbocation, the leaving group must be attached<br />
- 18 -
to either a tertiary or secondary carbon to stabilize the intermediate. A methyl or primary<br />
leaving group will not form a carbocation.<br />
Because the intermediate carbocation, R + , is planar, the central carbon is not a<br />
stereocenter, even if it was a stereocenter in the original reactant, so the original<br />
configuration at that atom is lost. Nucleophilic attack can occur from either side <strong>of</strong> the<br />
plane, so the product may consist <strong>of</strong> a mixture <strong>of</strong> two stereoisomers. In fact, if the<br />
central carbon is the only stereocenter in the reaction, racemization may occur<br />
General form <strong>of</strong> the S N 2 mechanism<br />
nuc: = nucleophile<br />
X = leaving group (usually halide)<br />
The S N 2 reaction involves displacement <strong>of</strong> a leaving group by a nucleophile. The<br />
rate <strong>of</strong> an S N 2 reaction is second order, as the rate-determining step depends on the<br />
nucleophile concentration, as well as the concentration <strong>of</strong> alkyl halide. This reaction<br />
works best with methyl <strong>and</strong> primary halides because bulky alkyl groups block the<br />
backside attack <strong>of</strong> the nucleophile, but the reaction does work with secondary halides<br />
(although it is usually accompanied by elimination), <strong>and</strong> will not react at all with tertiary<br />
halides. In the following example, the hydroxide ion is acting as the nucleophile <strong>and</strong><br />
bromide ion is the leaving group: Because <strong>of</strong> the backside attack <strong>of</strong> the nucleophile,<br />
inversion <strong>of</strong> configuration occurs.<br />
- 19 -
Experimental Procedure<br />
1. Reaction with NaI in acetone<br />
In this part <strong>of</strong> the experiment, you will test the reactivity <strong>of</strong> several alkyl halides in an<br />
S N<br />
2 reaction. Iodide ion (I - ) is an effective nucleophile in S N<br />
2 substitution. In acetone<br />
solution, other alkyl halides (alkyl chlorides or bromides) can be converted to alkyl<br />
iodides easily by this method. Although one might expect such a reaction to be<br />
reversible, it can be driven to formation <strong>of</strong> R-I by using anhydrous acetone as the<br />
solvent. Sodium iodide (NaI) is soluble in this solvent, but sodium chloride <strong>and</strong> sodium<br />
bromide are not. If a reaction occurs, a precipitate <strong>of</strong> sodium chloride or sodium<br />
bromide forms <strong>and</strong> thus the ion is not available in solution for the reverse reaction.<br />
The mechanism involves a one-step, concerted, S N<br />
2 reaction. Therefore, the reaction<br />
occurs most quickly when attack at the carbon that bears the halogen (X) is least<br />
sterically hindered.<br />
1. Place 2 drops <strong>of</strong> each <strong>of</strong> the following compounds in five separate clean <strong>and</strong><br />
dry test tubes. Label them accordingly.<br />
n-butyl chloride, s-butyl chloride, t-butyl chloride, n-butyl bromide, bromobenzene.<br />
2. Add 1 mL <strong>of</strong> 18% NaI solution in acetone in each test tube.<br />
3. Stopper, <strong>and</strong> shake vigorously.<br />
4. Record the time required to observe precipitate.<br />
• If no precipitation takes place after 5 minutes, place the test tube in a<br />
steam bath (45-50°C). Do not allow complete evaporation by adding<br />
acetone to keep the solution at the same level. Record whether the<br />
precipitation take place <strong>and</strong> the time required.<br />
• If no precipitation takes place after 10 minutes in steam bath, record<br />
data as “no precipitation”.<br />
5. Present the final result to your instructor.<br />
2. Reaction with AgNO 3 in ethanol<br />
The silver nitrate test allows for the identification <strong>of</strong> alkyl halides by observing them in<br />
an alcoholic silver nitrate environment. The rate at which the silver halide salt<br />
precipitate forms is characteristic <strong>of</strong> different types <strong>of</strong> alkyl halides. You will test the<br />
reactivity <strong>of</strong> several alkyl halides in a S N<br />
1 reaction. Organic halides may react with<br />
ethanol to form ethyl ethers. When the ethanol contains silver ion, the rate <strong>of</strong> reaction<br />
increases because the silver ion acts as an electrophile toward the halogen <strong>and</strong> helps<br />
to break the carbon-halogen bond. Alkyl chlorides yield an observable silver chloride<br />
precipitate, which is insoluble in ethanol <strong>and</strong> thus provides an indicator that a reaction<br />
has occurred. In this case, the slow step being the breaking <strong>of</strong> the carbon-halogen<br />
bond. The carbocation then reacts rapidly with alcohol to form the ether. Organic<br />
halide reactivity parallels the stability <strong>of</strong> the corresponding carbocations.<br />
1. Place 2 drops <strong>of</strong> each <strong>of</strong> the following compounds in five separate clean <strong>and</strong><br />
dry test tubes. Label the test tubes accordingly.<br />
- 20 -
n-butyl chloride, s-butyl chloride, t-butyl chloride, n-butyl bromide, bromobenzene.<br />
2. Add 1 mL <strong>of</strong> 1% AgNO 3 in ethanol.<br />
3. Stopper, <strong>and</strong> shake vigorously.<br />
4. Record the time required to observe precipitate. If no precipitation takes place<br />
after 5 minutes, place the test tube in a water bath (45-50°C). Do not allow<br />
complete evaporation by adding ethanol to keep the solution at the same<br />
level. Record whether the precipitation take place <strong>and</strong> the time required. If no<br />
precipitation takes place after 10 minutes in water bath, record data as “no<br />
precipitation”.<br />
5. Present the final result to your instructor.<br />
3. Comparison <strong>of</strong> SN1 <strong>and</strong> SN2<br />
Blank test:<br />
1. Place 1 mL <strong>of</strong> ethanol, 5 drops <strong>of</strong> water, <strong>and</strong> 2 drops <strong>of</strong> bromophenol blue in a<br />
test tube.<br />
2. Stopper <strong>and</strong> shake the tube vigorously.<br />
Note: Bromophenol blue pH 3 (yellow) – pH 4.6 (blue)<br />
Test A:<br />
1. Place 1 mL <strong>of</strong> ethanol, 5 drops <strong>of</strong> water, 2 drops <strong>of</strong> bromophenol blue, <strong>and</strong> 5<br />
drops <strong>of</strong> n-butyl chloride in a test tube.<br />
2. Stopper <strong>and</strong> shake the tube vigorously.<br />
3. Observe the result <strong>and</strong> compare with the blank test.<br />
4. Present the final result to your instructor.<br />
Test B:<br />
1. Place 1 mL <strong>of</strong> ethanol, 5 drops <strong>of</strong> water, 2 drops <strong>of</strong> bromophenol blue, <strong>and</strong> 5<br />
drops <strong>of</strong> t-butyl chloride in a test tube.<br />
2. Stopper <strong>and</strong> shake the tube vigorously.<br />
3. Observe the result <strong>and</strong> compare with the blank test.<br />
4. Present the final result to your instructor.<br />
4. Preparation <strong>of</strong> alkyl halide<br />
Alkyl halides may be prepared in a variety <strong>of</strong> ways, the particular method to be<br />
employed depending largely upon the nature <strong>of</strong> the alkyl group <strong>and</strong> the halogen.<br />
Some <strong>of</strong> the general methods which may be used are illustrated in the following<br />
equations:<br />
R-H + Cl 2 R-Cl + HCl<br />
R – CH=CH 2 + HCl R-CHCl-CH 3<br />
R-OH + HCl R-Cl + H 2 O<br />
ROH + SOCl 2 RCl + SO 2 + HCl<br />
Replacement <strong>of</strong> the hydroxyl group <strong>of</strong> an alcohol is perhaps the most common<br />
method. When the reagent is a hydrogen halide, the ease with which this may be<br />
accomplished increases as one proceeds from a primary to a tertiary alcohol. Tertiary<br />
alcohols are readily converted to the corresponding chlorides simply by shaking for a<br />
few minutes, at room temperature, with concentrated hydrochloric acid.<br />
- 21 -
Synthesis <strong>of</strong> Tertiary Butyl Chloride<br />
1. Place 10 mL <strong>of</strong> cold concentrated hydrochloric acid in a 125 mL separatory<br />
funnel.<br />
2. Add 5 mL <strong>of</strong> tert-butyl alcohol<br />
3. Without closing the separatory funnel, mix the two components by swirling the<br />
funnel for a few minutes.<br />
4. Close the separatory funnel with its stopper, shake the separatory funnel at<br />
intervals for 10 minutes. From time to time, relieve any internal pressure by<br />
inverting the funnel <strong>and</strong> slowly opening the stopcock.<br />
5. Allow the mixture to st<strong>and</strong> until two distinct layers separate.<br />
6. Draw <strong>of</strong>f <strong>and</strong> discard the aqueous layer (bottom layer) through the stopcock.<br />
7. Add 15 mL <strong>of</strong> distilled water, shake the separatory funnel for 30 seconds, put the<br />
funnel on the st<strong>and</strong> <strong>and</strong> relieve the pressure by opening the stopper.<br />
8. Allow the mixture to st<strong>and</strong> until two distinct layers separate.<br />
9. Draw <strong>of</strong>f <strong>and</strong> discard the aqueous layer (bottom layer) through the stopcock.<br />
10. Add 15 mL <strong>of</strong> distilled water, shake the separatory funnel for 30 seconds, put the<br />
funnel on the st<strong>and</strong> <strong>and</strong> relieve the pressure by opening the stopper.<br />
11. Allow the mixture to st<strong>and</strong> until two distinct layers separate.<br />
12. Draw <strong>of</strong>f <strong>and</strong> discard the aqueous layer (bottom layer) through the stopcock.<br />
13. Weigh <strong>and</strong> record the weight <strong>of</strong> an empty clean test tube.<br />
14. Draw <strong>of</strong>f the organic layer (your product) into the test tube. Weigh the tube with<br />
your product.<br />
15. Calculate <strong>and</strong> record the weight <strong>of</strong> your product.<br />
16. Calculate the % yield <strong>of</strong> the product.<br />
17. In order to verify the identity <strong>of</strong> your product, test the product with both NaI <strong>and</strong><br />
AgNO 3 (follow the procedures 1-2 above)<br />
18. Present the final result to your instructor.<br />
- 22 -
Experiment<br />
6<br />
Alcohols <strong>and</strong> Phenols<br />
by Paitoon Rashatasakhon<br />
Objectives<br />
1) To classify alcohols according to their characteristic chemical reactions.<br />
2) To differentiate phenols <strong>and</strong> the three types <strong>of</strong> alcohols using simple chemical tests.<br />
Principles<br />
The alcohols, with a hydroxyl group attached to an alkyl chain, <strong>and</strong> the phenols,<br />
with the same group attached directly to the aromatic ring, have similar chemical<br />
properties in kind, but may differ considerably in the degree to which these properties are<br />
exhibited. Alcohols are classified as 1 0 , 2 0 <strong>and</strong> 3 0 , depending on the number <strong>of</strong> carbon<br />
atoms connected to the carbon bearing the OH group. The following experiments are<br />
designed to bring out these similarities <strong>and</strong> differences, as well as to demonstrate the<br />
properties <strong>of</strong> the hydroxyl group.<br />
Examples <strong>of</strong> primary alcohols<br />
OH<br />
OH<br />
OH<br />
OH<br />
Examples <strong>of</strong> secondary alcohols<br />
OH<br />
OH OH CH 2 Ph<br />
H OH<br />
Cl H<br />
CH 3<br />
Examples <strong>of</strong> tertiary alcohols<br />
OH<br />
OH<br />
OH<br />
OH<br />
CH 3<br />
Examples <strong>of</strong> phenolic compounds<br />
OH<br />
OH<br />
OH<br />
HO<br />
OCH 3<br />
HO<br />
- 23 -
Experimental Procedures<br />
1) Water solubility<br />
The more carbon atoms present in the molecule <strong>of</strong> alcohols, the less polar <strong>and</strong><br />
more hydrophobic they become. However, alcohols with straight chain methylene (-CH 2 -)<br />
units are generally more hydrophobic than those with branch structure.<br />
1. Place 2 drops <strong>of</strong> each <strong>of</strong> the following compounds in six separate clean test tubes.<br />
Label them accordingly.<br />
ethanol, 1-butanol, 2-butanol, tert-butanol, cyclohexanol, phenol<br />
2. Add 10 drops <strong>of</strong> water into each test tube. Shake <strong>and</strong> let st<strong>and</strong>.<br />
3. Observe whether the compound is soluble in water.<br />
4. Record the data <strong>and</strong> present to your instructor.<br />
2) Alkali solubility<br />
Alcohols are weaker acids than water, but the aromatic ring makes phenols more<br />
acidic than water, which means that they may be neutralized by stronger bases such as<br />
sodium hydroxide.<br />
1. Place 2 drops <strong>of</strong> each <strong>of</strong> the following compounds in three separate clean test tubes.<br />
Label them accordingly.<br />
1-butanol, cyclohexanol, phenol<br />
2. Add 10 drops <strong>of</strong> 10% NaOH solution into each test tube. Shake <strong>and</strong> let st<strong>and</strong>.<br />
3. Observe whether the compound is soluble in NaOH solution.<br />
4. Record the data <strong>and</strong> present to your instructor.<br />
3) Reaction with metallic sodium<br />
The hydrogen atom <strong>of</strong> the hydroxyl group can be displaced by active metals such<br />
as sodium. This reaction can be used as an indication <strong>of</strong> the presence <strong>of</strong> an –OH group in<br />
an unknown compound. The reaction produces hydrogen gas <strong>and</strong> the corresponding<br />
sodium alkoxide as shown in the following equation.<br />
OH<br />
+ Na<br />
O - Na + + H 2<br />
tert-butanol<br />
sodium<br />
sodium tert-butoxide<br />
hydrogen<br />
1. Place 10 drops <strong>of</strong> each <strong>of</strong> the following compounds in three separate clean <strong>and</strong> dry<br />
test tubes. Label them accordingly.<br />
ethanol, 2-propanol,<br />
tert-butanol<br />
2. Add a very small piece <strong>of</strong> sodium into each test tube.<br />
3. Observe the result <strong>and</strong> note the relative rates <strong>of</strong> reaction (gas bubbling).<br />
4. Add a drop <strong>of</strong> phenolphthalein to the ethanol tube (only one tube).<br />
5. Observe the result.<br />
6. Record the data <strong>and</strong> present to your instructor.<br />
- 24 -
NOTE: Do not discard the waste from the experiment into the sink. Discard the<br />
solution into the bottle or beaker labeled “Sodium Waste”.<br />
4) Reaction with ceric nitrate<br />
Alcohols with less than 10 carbon atoms can form colorful complexes with Ce 3+<br />
ion. This is a characteristic feature <strong>of</strong> alcohols as the positive test results will have<br />
different color compared to the blank test.<br />
1. Place 2 drops <strong>of</strong> each <strong>of</strong> the following compounds in four separate clean <strong>and</strong> dry test<br />
tubes. Label them accordingly.<br />
1-butanol, 2-butanol, tert-butanol, phenol<br />
2. Add 1 mL <strong>of</strong> ceric nitrate reagent into each test tube.<br />
3. Observe the result <strong>and</strong> compare the color with blank test (ceric nitrate reagent + a<br />
few drops <strong>of</strong> water)<br />
4. Present the data to your instructor<br />
5) Characteristic reactions <strong>of</strong> phenol<br />
a) Phenols <strong>and</strong> compounds with the hydroxyl group attached to an unsaturated<br />
carbon atom, give coloration (purple/violet) upon the addition <strong>of</strong> ferric chloride<br />
(FeCl 3 ) solution. This is due to the formation <strong>of</strong> complex between phenolic<br />
compounds <strong>and</strong> Fe 3+ ion.<br />
1. Place 1 mL <strong>of</strong> water into each <strong>of</strong> two clean test tubes.<br />
2. Add one drop <strong>of</strong> phenol in one tube <strong>and</strong> a few drops <strong>of</strong> ethanol in the other.<br />
3. Add 5 drops <strong>of</strong> 1% ferric chloride solution. Note the characteristic color developed in<br />
the phenol tube. This is a st<strong>and</strong>ard test for most phenol.<br />
4. Present the data to your instructor<br />
b) The hydroxyl group <strong>of</strong> the phenols activates the benzene ring to further<br />
substitution. Bromination using bromine water can proceed smoothly under very<br />
mild conditions.<br />
1. Place 1 mL <strong>of</strong> water into each <strong>of</strong> two clean test tubes.<br />
2. Add one drop <strong>of</strong> phenol in one tube <strong>and</strong> a few drops <strong>of</strong> ethanol in the other.<br />
3. Add bromine water slowly into each tube. If the color disappears, continue adding<br />
until the color <strong>of</strong> the bromine just persists.<br />
4. Present the data to your instructor<br />
6) Lucas test –Differentiation <strong>of</strong> primary, secondary <strong>and</strong> tertiary alcohols<br />
The Lucas test is a test for the ease <strong>of</strong> replacement <strong>of</strong> a hydroxyl group by a<br />
halogen atom, according to the reaction:<br />
R OH<br />
+ HCl<br />
ZnCl 2<br />
R Cl + H 2 O<br />
Since the product (alkyl halide) is insoluble in water, the solution becomes cloudy<br />
<strong>and</strong> may separate into two layers when the hydroxyl group is replaced with halogen. This<br />
cloudiness or appearance <strong>of</strong> a second layer (heterogeneous mixture) is evidence that a<br />
reaction has occurred.<br />
- 25 -
When Lucas reagent (ZnCl 2 + conc. HCl) is added to alcohols, H + from HCl will<br />
protonate the -OH group, so that the leaving group H 2 O, being a much weaker<br />
nucleophile than OH - , hence can be substituted by nucleophile Cl - . Lucas' reagent <strong>of</strong>fers<br />
a polar medium in which S N 1 mechanism is favored. In unimolecular nucleophilic<br />
substitution, the reaction rate is faster when the carbocation intermediate is more stable.<br />
Therefore, tertiary alcohols react immediately with Lucas reagent to produce turbidity<br />
while secondary alcohols do so in about five minutes. Primary alcohols do not react<br />
appreciably with Lucas reagent at room temperature. Hence, the time taken for turbidity to<br />
appear is a measure <strong>of</strong> the reactivity <strong>of</strong> the class <strong>of</strong> alcohol with Lucas reagent, <strong>and</strong> this is<br />
used to differentiate between the three classes <strong>of</strong> alcohols<br />
1. Place 3 drops <strong>of</strong> each <strong>of</strong> the following compounds in four separate clean <strong>and</strong> dry test<br />
tubes. Label the test tubes accordingly.<br />
1-butanol, cyclohexanol, tert-butanol<br />
2. Add 1 mL <strong>of</strong> the Lucas reagent into each tube.<br />
3. Stopper <strong>and</strong> shake well.<br />
4. Observe the result immediately, after 5 min, <strong>and</strong> again after 30 min.<br />
5. Present the data to your instructor.<br />
7) The oxidation reaction<br />
The oxidation <strong>of</strong> the carbon atom is an important reaction for this class <strong>of</strong><br />
compounds. When sodium dichromate is used as an oxidizing agent, the orange<br />
dichromate ion is reduced to the green chromic ion. In this reaction a chromate ester <strong>of</strong><br />
the alcohol substrate is believed to be an intermediate, which undergoes an E2-like<br />
elimination to the carbonyl product. The oxidation state <strong>of</strong> carbon increases by 2, while<br />
the chromium decreases by 3 (it is reduced). The progress <strong>of</strong> these oxidations is easily<br />
observed. Indeed, this is the chemical transformation on which the Breathalyzer test is<br />
based. The secondary alcohols can be oxidized to ketones, while the oxidation <strong>of</strong> primary<br />
alcohols initially gives aldehydes which are oxidized further to carboxylic acids. Tertiary<br />
alcohols will not be oxidized under these conditions.<br />
1. Place 0.5 mL <strong>of</strong> a 10% solution <strong>of</strong> sodium dichromate in a clean test tube.<br />
2. Add 2 drops <strong>of</strong> concentrated sulfuric acid <strong>and</strong> stir with a glass rod.<br />
3. Add 5 drops <strong>of</strong> ethanol <strong>and</strong> warm gently (~40-50°C).<br />
4. Observe any change in color <strong>of</strong> the solution.<br />
5. Repeat step 1-4 with 2-propanol <strong>and</strong> tert-butanol.<br />
6. Present the data to your instructor.<br />
8) Identification <strong>of</strong> an unknown alcohol.<br />
After presenting the data from part 1-6 to your instructor, you will receive an<br />
unknown alcohol. Identify the possible structure <strong>of</strong> your unknown based on the data<br />
from ceric nitrate test, FeCl 3 test, Lucas test, <strong>and</strong> oxidation test.<br />
- 26 -
Experiment<br />
7<br />
Aromatic Chemistry –<br />
Nitration <strong>of</strong> Methyl Benzoate<br />
by Varawut Tangpasuthadol<br />
Objectives<br />
1) To perform nitration reaction <strong>of</strong> methyl benzoate.<br />
2) To purify the product by recrystallization.<br />
3) To analyze the purity <strong>of</strong> the product by TLC <strong>and</strong> melting point determination.<br />
Principles<br />
Nitration <strong>of</strong> methyl benzoate is a classic example <strong>of</strong> the electrophilic aromatic<br />
substitution reaction. In general, the electron-rich aromatic ring is attracted to<br />
electrophiles, which in this case is a ‘nitronium’ ion (NO 2 + ). The nitronium ion is<br />
generated from a mixture <strong>of</strong> concentrated nitric acid <strong>and</strong> concentrated sulfuric acid as<br />
shown below.<br />
HNO 3 + H 2 SO 4 NO + -<br />
2 + HSO 4<br />
nitronium iom<br />
O<br />
+ H 2 O<br />
O<br />
C<br />
OCH3<br />
+ NO 2<br />
+<br />
H 2 SO 4<br />
15 o C<br />
C<br />
OCH3<br />
NO 2<br />
Methyl m-nitrobenzoate<br />
The –CO 2 CH 3 group on methyl benzoate is an electron withdrawing group <strong>and</strong> is<br />
therefore considered as a meta-directing group. If the reaction condition is very well<br />
controlled as directed, methyl m-nitrobenzoate should be the only product obtained from<br />
this reaction, otherwise by-products such as a di-nitro compound may occur. For this<br />
reason, students are also asked to check the purity <strong>of</strong> the product by performing TLC <strong>of</strong><br />
their synthesized product.<br />
Chemicals<br />
Methyl benzoate 10 drops (~200 mg) irritate, flammable<br />
Conc. sulfuric acid 3 mL<br />
corrosive, reacts violently with water<br />
Conc. nitric acid 1 mL corrosive, oxidizing agent<br />
- 27 -
Experimental Procedure<br />
1) Withdraw 10 drops <strong>of</strong> methyl benzoate from a burette into a small conical flask<br />
with known weight. Record the exact weight <strong>of</strong> methyl benzoate used.<br />
2) Immerse the flask from step 1 in an ice-water bath. Slowly add 2 mL <strong>of</strong><br />
concentrated sulfuric acid dropwise while swirling.<br />
3) Prepare the nitrating agent by mixing 1.0 mL <strong>of</strong> conc. sulfuric acid <strong>and</strong> 1.0 mL <strong>of</strong><br />
conc. nitric acid in a test tube that is chilled in an ice-water bath.<br />
4) SLOWLY add, using a Pasteur pipet, the solution from step 3 into the mixture from<br />
step 2 while being chilled all the time. Stir the mixture regularly. The adding period<br />
should not be less than 15 minutes. If the mixture becomes cloudy, add a few<br />
drops <strong>of</strong> conc. sulfuric acid until the solution is clear.<br />
5) Let the reaction mixture st<strong>and</strong> in a water bath (no ice) at room temperature for 15<br />
minutes.<br />
6) Add about 10 g <strong>of</strong> crushed ice into the reaction mixture. Stir the mixture vigorously.<br />
7) After the ice has melted, isolate the solid product by vacuum filtration <strong>and</strong> wash<br />
with cool water, 5% NaHCO 3 , <strong>and</strong> cool water again until the filtrate is neutral.<br />
8) Dry the product in a watch glass over a steam bath, weigh <strong>and</strong> determine yield<br />
percentage <strong>of</strong> the product (before re-crystallization).<br />
9) Re-crystallize the product from methanol. (Use a minimum amount <strong>of</strong> hot methanol<br />
to dissolve the product.)<br />
10) Weigh the re-crystallized product. Calculate yield percentage after recrystalization<br />
<strong>and</strong> recovery percentage.<br />
11) Check the purity <strong>of</strong> the product by TLC comparing to the starting material. A<br />
mixture <strong>of</strong> hexane-ethyl acetate (3:1) is used as the eluent.<br />
12) Determine the melting point <strong>of</strong> the purified product <strong>and</strong> compare it with a<br />
reference.<br />
13) Submit the product to your instructor in a labeled plastic bag.<br />
Waste Disposal<br />
All organic solvent wastes are discarded in a container marked, ‘Organic Waste’.<br />
- 28 -
Experiment<br />
8<br />
Aldehydes <strong>and</strong> Ketones<br />
by Varawut Tangpasuthadol<br />
Objective<br />
To carry out a series <strong>of</strong> chemical reactions for the classification <strong>of</strong> aldehydes <strong>and</strong><br />
ketones.<br />
Principles<br />
Aldehydes <strong>and</strong> ketones are organic compounds that contain carbonyl functional groups<br />
connecting to either one hydrogen <strong>and</strong> one alkyl (or aryl) group or two alkyl (or aryl)<br />
groups, respectively.<br />
O<br />
O<br />
R C H R C R' R C CH R'<br />
O<br />
OH<br />
O<br />
R C CH 3<br />
Aldehyde ketone α-hydroxy ketone methyl ketone<br />
The chemistry <strong>of</strong> these compounds is primarily due to that <strong>of</strong> the carbonyl<br />
groups. Identifying methods for aldehydes <strong>and</strong> ketones can be performed by a number<br />
<strong>of</strong> chemical reagents listed in Table 1.<br />
Table 1 Classification tests for aldehydes <strong>and</strong> ketones<br />
Compound<br />
Aldehydes <strong>and</strong> ketones<br />
Aldehydes, α-hydroxy ketones<br />
Aliphetic aldehydes, α-hydroxy ketones<br />
Aldehydes<br />
Aldehydes, α-hydroxy ketones<br />
Methyl ketone, acetaldehyde<br />
Reagent<br />
2,4-Dinitrophenylhydrazine<br />
Tollen’s reagent<br />
Benedict’s reagent<br />
Schiff’s reagent<br />
Potassium permanganate<br />
Iod<strong>of</strong>orm test<br />
Classification tests<br />
2,4-Dinitrophenylhydrazine (2,4-DNP) reagent<br />
Most aldehydes <strong>and</strong> ketones give a precipitate, 2,4-dinitrophenylhydrazone. The<br />
color <strong>of</strong> the precipitate is ranged from yellow-orange-red. The color <strong>of</strong> any precipitate<br />
must be judged cautiously, since the 2,4-DNP reagent is itself orange-red. Glucose <strong>and</strong><br />
other carbohydrates also give positive results for this test but very slowly, therefore,<br />
boiling is also required.<br />
- 29 -
O<br />
R C R' +<br />
H 2 N<br />
H<br />
N<br />
NO 2<br />
NO 2<br />
2,4-dinitrophenylhydrazine<br />
H +<br />
R<br />
R'<br />
N<br />
NH<br />
NO 2<br />
NO 2<br />
2,4-dinitrophenylhydrazone<br />
+ H 2 O<br />
Tollen’s test<br />
Most aldehydes, α-hydroxy ketone <strong>and</strong> more carbohydrates can reduce silver<br />
nitrate (AgNO 3 ) solution in ammonia to give silver metal (Ag). The silver may precipitate<br />
as ‘silver mirror’ along the side <strong>of</strong> a test tube or as gray powder. The aldehyde is<br />
oxidized to a carboxylic acid:<br />
RCHO + 2 Ag(NH 3 ) 2 OH 2 Ag (s) + RCOO - NH 4 + + H 2 O + NH 3<br />
Benedict’s test<br />
Only aliphatic aldehydes <strong>and</strong> α-hydroxy ketone can be oxidized by copper (II) ion<br />
(Cu 2+ ) to give orange-red precipitate <strong>of</strong> cupric oxide (Cu 2 O). For some compounds,<br />
green, blue or brown precipitate can also be expected. Reducing sugars such as<br />
glucose, fructose, mannose, lactose <strong>and</strong> maltose can also be oxidized by the Benedict’s<br />
test.<br />
RCHO + 2 Cu 2+ + 5 OH -<br />
RCOO - + Cu 2 O (s) + 3 H 2 O<br />
Schiff’s test<br />
Schiff’s reagent is a solution <strong>of</strong> pararosaniline hydrochloride which is reacted with<br />
sulfuric acid to give a colorless solution. This solution will turn light purple or pink when<br />
reacting with an aldehyde.<br />
Potassium permanganate test<br />
Potassium permanganate solution contains manganese (VII) ion (Mn 7+ ) that can<br />
oxidize aldehydes <strong>and</strong> α-hydroxy ketone to carboxylic compounds <strong>and</strong> di-ketone,<br />
respectively. A brown precipitate <strong>of</strong> manganese dioxide (MnO 2 ) is observed.<br />
Iod<strong>of</strong>orm test<br />
Methyl ketone <strong>and</strong> acetaldehyde form a precipitate <strong>of</strong> iod<strong>of</strong>orm (CHI 3 ) when<br />
treated with a basic solution <strong>of</strong> iodine. The iod<strong>of</strong>orm is yellow in color <strong>and</strong> may be<br />
produced in a very small amount. Therefore, the testing result should be carefully<br />
observed since the yellow precipitate usually sinks to the bottom <strong>of</strong> the test tubes.<br />
CH 3<br />
O<br />
C<br />
R'<br />
I 2<br />
NaOH<br />
CI 3<br />
O<br />
C<br />
R'<br />
OH -<br />
O<br />
- O C R'<br />
+ CHI 3<br />
iod<strong>of</strong>orm<br />
Test samples<br />
Acetaldehyde, acetone, benzaldehyde, glucose (1% solution in water), benzoin (1%<br />
solution in ethanol), <strong>and</strong> one UNKNOWN sample<br />
- 30 -
Experimental Procedure<br />
Note- A blank test should be performed in every test.<br />
1) Reaction with 2,4-dinitrophenylhydrazine (2,4-DNP)<br />
Place one drop <strong>of</strong> a test sample in a test tube <strong>and</strong> add 1 mL <strong>of</strong> 2,4-DNP. Shake the<br />
solution well. If no precipitation is observed, gently heat the sample test tube about 15<br />
minutes. Compare the appearance <strong>of</strong> the precipitate <strong>and</strong> the time required for the<br />
precipitation <strong>of</strong> all test samples.<br />
2) Tollen’s reagent<br />
Place 2 drops <strong>of</strong> a test sample in a test tube. Add 1 mL Tollen’s reagent. Shake the<br />
solution well. If a mirror <strong>of</strong> silver is deposited on the inner walls <strong>of</strong> the test tube, the test<br />
is positive. Otherwise heat the test tube for 1 minute, let it cool down to room<br />
temperature. Record the change in appearance.<br />
3) Schiff’s reagent<br />
Place 1 mL Schiff’s reagent in a test tube. Add 1 drop <strong>of</strong> a test sample. Shake the<br />
solution. Record the result.<br />
4) Benedict’s test<br />
In a test tube, place 1 mL Benedict’s solution <strong>and</strong> add 1 drop <strong>of</strong> a test sample. Shake<br />
the solution well. If there is no change, warm up the test tube for about 5 minutes.<br />
Record the result.<br />
5) Oxidation with KMnO 4<br />
Place 4 drops <strong>of</strong> test sample in a test tube. Add 2 drops <strong>of</strong> 0.1% KMnO 4 solution. Shake<br />
the solution well. Record the result.<br />
6) Iod<strong>of</strong>orm test<br />
Use only acetaldehyde, acetone <strong>and</strong> benzaldehyde for this test.<br />
Place 1 mL distilled water in each <strong>of</strong> 4 test tubes. Add one drop <strong>of</strong> the test sample in<br />
each tube. Add 1 mL <strong>of</strong> 5% NaOH solution. Add iodine-potassium iodide (I 2 -KI) solution<br />
one drop at a time until a permanent pale yellow solution is obtained. Shake the tube<br />
well after each addition. Allow the test tube to st<strong>and</strong> for 2-3 minutes. If the test is<br />
positive, the yellow solution will decolorize <strong>and</strong> a yellow precipitate <strong>of</strong> iod<strong>of</strong>orm will form.<br />
If the color <strong>of</strong> the solution is discharged but no precipitation, add some more I 2 -KI<br />
solution until the pale yellow color returns. Allow the solution to st<strong>and</strong> for 2 more<br />
minutes. It may be necessary to warm the solution in a water bath (~60 °C) to aid in the<br />
discharge <strong>of</strong> the color.<br />
7) Classification test for an unknown compound<br />
Obtain an unknown sample from the instructor. Record the sample number. Perform the<br />
tests according to the procedure. From the results, try to identify the detailed structure<br />
<strong>of</strong> the unknown. Consult with your instructor <strong>and</strong> write down the structure in the report.<br />
- 31 -
Experiment<br />
9<br />
Synthesis <strong>of</strong> Esters <strong>and</strong> Reactions <strong>of</strong><br />
Carboxylic Acids <strong>and</strong> their Derivatives<br />
by Warinthorn Chavasiri<br />
Objectives<br />
1) To synthesize an ester using acid-catalyzed esterification reaction.<br />
2) To study the reactions <strong>of</strong> carboxylic acids <strong>and</strong> their derivatives.<br />
Principles<br />
Carboxylic acid is an important class <strong>of</strong> organic compounds. Acid derivatives differ<br />
from their parent compound in that the hydroxyl (-OH) portion is replaced by another<br />
group. Important acid derivatives include acid halides, anhydrides, esters, <strong>and</strong> amides.<br />
O<br />
R<br />
C<br />
OH<br />
carboxylic acid<br />
O<br />
O<br />
O<br />
O<br />
O<br />
R<br />
C<br />
X<br />
R<br />
C<br />
O<br />
C<br />
R<br />
R<br />
C<br />
OR'<br />
R<br />
C<br />
NH 2<br />
acid halide<br />
anhydride<br />
ester<br />
amide<br />
Carboxylic acids can be converted into their salts by treatment with base. Because<br />
these salts are ionic <strong>and</strong> usually water-soluble, acids have low solubility in the presence<br />
<strong>of</strong> base in water can be extracted from a solution into an organic solvent.<br />
O<br />
O<br />
R<br />
C<br />
less soluble<br />
in water<br />
OH + NaOH R C<br />
O - Na +<br />
more soluble<br />
in water<br />
+ H 2 O<br />
Acid halides are usually prepared by reacting the corresponding acid with an<br />
inorganic halide such as PCl 3 , PCl 5 or thionyl chloride (SOCl 2 ). Acid anhydrides can be<br />
prepared by dehydration <strong>of</strong> the corresponding carboxylic acids. The acid-catalyzed<br />
reaction <strong>of</strong> an alcohol with a carboxylic acid is the most commonly used method for ester<br />
preparation. Amides can be prepared by heating ammonium salts <strong>of</strong> acids or by the<br />
reaction <strong>of</strong> ammonia, primary-, or secondary-amines with various acid derivatives. Most<br />
reactions <strong>of</strong> acid derivatives involve nucleophilic attack on the carbonyl carbon.<br />
- 32 -
Preparation <strong>of</strong> an ester<br />
Background<br />
Esters are found in many natural products, contributing to the scent <strong>of</strong> banana,<br />
orange, pineapple, <strong>and</strong> other fruits. The structure <strong>of</strong> ester determines its scent. By<br />
reacting different alcohols with carboxylic acids, you can produce esters <strong>of</strong> different<br />
scents. There are many different methods for synthesizing esters. However, the two<br />
most common ones are 1) acid-catalyzed Fischer esterification using a carboxylic acid<br />
<strong>and</strong> an alcohol; <strong>and</strong> 2) condensation <strong>of</strong> acid chloride with an alcohol.<br />
The Fischer esterification is an equilibrium reaction in which an acid <strong>and</strong> an alcohol<br />
combine to produce the ester <strong>and</strong> water. For example, the acid catalyzed reaction for<br />
the formation <strong>of</strong> ethyl acetate from acetic acid <strong>and</strong> ethanol.<br />
H 3 C<br />
O<br />
C<br />
OH<br />
+ CH 3 CH 2 OH<br />
H+<br />
H 3 C<br />
O<br />
C<br />
OCH 2 CH 3<br />
+ H 2 O<br />
To drive the equilibrium towards completion, either the starting carboxylic acid or the<br />
alcohol is used in excess. Alternatively, if the ester has a significantly different boiling<br />
point than the alcohol or acid, it can be separated from the acid <strong>and</strong> alcohol by<br />
distillation.<br />
The second synthetic route to esters employs an acid chloride, which has to be<br />
prepared in an additional step. The reaction requires a base such as K 2 CO 3 or<br />
triethylamine to destroy the hydrochloric acid by-product.<br />
O<br />
O<br />
H 3 C<br />
C<br />
base<br />
Cl + CH 3 CH 2 OH H 3 C C<br />
OCH 2 CH 3<br />
Techniques<br />
Reflux<br />
Extraction using separatory funnel<br />
Simple distillation<br />
- 33 -
Experimental Procedure<br />
Part A Preparation <strong>of</strong> fruity ester (CARE: extremely corrosive)<br />
Each group will obtain an unknown carboxylic acid <strong>and</strong> an unknown alcohol. You will<br />
then synthesize an ester from the two starting materials, identify the scent <strong>of</strong> the ester<br />
product, purify the product by distillation, <strong>and</strong> predict the identity <strong>of</strong> the two starting<br />
materials based on the scent <strong>of</strong> the ester <strong>and</strong> its boiling point.<br />
Procedure<br />
1. Pour all <strong>of</strong> the unknown alcohol <strong>and</strong> carboxylic acid into a 50 mL round bottom<br />
flask. The alcohol was accurately measured to be 0.046 mol <strong>and</strong> the carboxylic<br />
acid was measured to be 0.12 mol.<br />
2. Carefully add 1.5 mL <strong>of</strong> concentrated sulfuric acid to the reaction flask. Add<br />
boiling stones to the mixture.<br />
3. Assemble the reflux apparatus. Bring the mixture to boil using a heating mantle<br />
<strong>and</strong> heat the mixture under reflux for 1 hour. During this time, you may proceed<br />
to Part B.<br />
4. Remove the heating source <strong>and</strong> allow the mixture to cool to room temperature.<br />
5. Pour the cooled mixture into a separatory funnel <strong>and</strong> carefully add 20 mL <strong>of</strong><br />
distilled water. Rinse the reaction flask with 5 mL <strong>of</strong> distilled water <strong>and</strong> pour the<br />
rinsing into the separatory funnel.<br />
6. Stopper the funnel <strong>and</strong> shake it several times. Separate the lower aqueous layer<br />
from the upper organic layer. Label the unwanted aqueous layer <strong>and</strong> put it aside.<br />
7. The crude ester in the upper organic layer still contains some unreacted acid<br />
which can be removed by extraction with NaHCO 3 solution. Carefully add 10 mL<br />
<strong>of</strong> 5% NaHCO 3 to the organic layer in the separatory funnel. Without the stopper,<br />
swirl the funnel gently until carbon dioxide gas no longer evolved.<br />
8. Place the stopper, shake the funnel, relief the internal pressure, <strong>and</strong> settle the<br />
funnel to allow phase separation to occur, then remove <strong>and</strong> discard the lower<br />
layer.<br />
9. Add 10 mL <strong>of</strong> 5% NaHCO 3 to the organic layer in the separatory funnel. Place<br />
the stopper, shake the funnel, relief the internal pressure, <strong>and</strong> settle the funnel to<br />
allow phase separation to occur.<br />
10. Remove the lower layer <strong>and</strong> check whether it is basic to litmus paper. If it is not<br />
basic, repeat step 9 until the aqueous layer is basic.<br />
11. Add 10-mL portion <strong>of</strong> water. Place the stopper, shake the funnel, relief the<br />
internal pressure, <strong>and</strong> settle the funnel to allow phase separation.<br />
12. Add 10 mL <strong>of</strong> saturated sodium chloride to aid in layer separation.<br />
13. Carefully separate <strong>and</strong> discard the lower layer.<br />
- 34 -
14. Transfer the organic layer into an Erlenmeyer flask. Add about 2 g <strong>of</strong> anhydrous<br />
MgSO 4 to dry the solution.<br />
15. Assemble a simple distillation apparatus <strong>and</strong> carefully decant the ester solution<br />
into the distillating flask.<br />
16. Add boiling stones <strong>and</strong> distill the ester. Collect the fraction <strong>and</strong> observe the<br />
boiling range.<br />
17. Weigh the product.<br />
18. Report the scent <strong>and</strong> boiling point <strong>of</strong> your ester product to your instructor. Also,<br />
identify the unknown starting carboxylic acid <strong>and</strong> alcohol.<br />
19. Calculate the percentage yield based on the molecular weight <strong>of</strong> your product.<br />
- 35 -
Table <strong>of</strong> selected ester flavors <strong>and</strong> fragrances<br />
Complete this table before starting the experiments.<br />
Draw the structures <strong>of</strong> the carboxylic acids, alcohols <strong>and</strong> esters.<br />
Find out the boiling range <strong>of</strong> the esters from the references.<br />
Carboxylic Alcohol Ester Scent b.p.<br />
acid<br />
Acetic acid Isoamyl alcohol Isoamyl acetate banana<br />
Propionic acid Isobutyl alcohol Isobutyl propionate rum<br />
Anthranilic<br />
acid<br />
Methyl alcohol Methyl anthranilate grape<br />
Acetic acid Benzyl alcohol Benzyl acetate peach<br />
Butyric acid Methyl alcohol Methyl butyrate apple<br />
Butyric acid Ethyl alcohol Ethyl butyrate pineapple<br />
Acetic acid Octyl alcohol Octyl acetate orange<br />
Acetic acid n-Propyl alcohol n-Propyl acetate pear<br />
- 36 -
Part B<br />
Reactions <strong>of</strong> carboxylic acids <strong>and</strong> their derivatives<br />
Samples:<br />
O<br />
H OH<br />
Formic acid<br />
O<br />
H 3 C OH<br />
Acetic acid<br />
O<br />
O<br />
OH<br />
OH<br />
Oxalic acid<br />
O OH O OCH 3<br />
Benzoic acid<br />
Methyl benzoate<br />
O<br />
HN CH 3<br />
Acetanilide<br />
1. Solubility Experiments<br />
a) In water<br />
Add approximately 2 drops <strong>of</strong> liquid sample or 0.1 g <strong>of</strong> solid sample into water<br />
(3 mL). Shake well, observe the solubility, <strong>and</strong> record your observation.<br />
b) In 5% NaOH solution<br />
Use the same amount <strong>of</strong> sample as above, <strong>and</strong> use 3 mL <strong>of</strong> 5% NaOH solution.<br />
Observe the solubility in 5% NaOH solution <strong>and</strong> record your observation.<br />
c) In 5% NaHCO 3 solution<br />
Use the same amount <strong>of</strong> sample as above, <strong>and</strong> use 5% NaHCO 3 solution.<br />
Observe the solubility in 5% NaHCO 3 <strong>and</strong> look for evolution <strong>of</strong> gas.<br />
2. Ferric hydroxamate reaction<br />
Place a drop <strong>of</strong> methyl benzoate in a test tube <strong>and</strong> add 0.5 M NH 2 OH.HCl in<br />
ethanol (1 mL). Add 20% NaOH until the solution becomes basic to litmus. Warm<br />
up the mixture on the water bath for 5 min <strong>and</strong> then cool down to room<br />
temperature. Add 1M HCl until the solution becomes acidic or the brown<br />
precipitate dissolves. Add 5% FeCl 3 until a permanent color is observed. Record<br />
your observation <strong>and</strong> then repeat with benzoic acid.<br />
3. Reaction with Tollens’ reagent<br />
Place approximately 4 mL <strong>of</strong> Tollens’ reagent in each <strong>of</strong> 5 test tubes <strong>and</strong> add in<br />
the samples in the first four tubes as listed in the table below. The last tube is<br />
used as a blank test.<br />
Tube # Tollens’s reagent (mL) Sample<br />
1<br />
2<br />
3<br />
4<br />
5<br />
4<br />
4<br />
4<br />
4<br />
4<br />
Formic acid (5 drops)<br />
Acetic acid (5 drops)<br />
Oxalic acid (0.1 g)<br />
Benzoic acid (0.1 g)<br />
- = blank test<br />
Place the tubes in water bath for 5 min <strong>and</strong> compare with the blank test. Record<br />
your observation.<br />
- 37 -
4. Reaction with KMnO 4<br />
Place approximately 1 mL <strong>of</strong> distilled water in each <strong>of</strong> 5 test tubes <strong>and</strong> add in the<br />
reagents <strong>and</strong> samples as listed in the table below. The last tube is used as a<br />
blank test.<br />
Tube<br />
#<br />
Water (mL)<br />
Conc.<br />
H 2 SO 4<br />
(drop)<br />
0.3%<br />
KMnO 4<br />
(mL)<br />
Sample<br />
1<br />
2<br />
3<br />
4<br />
5<br />
4<br />
4<br />
4<br />
4<br />
4<br />
1<br />
1<br />
1<br />
1<br />
1<br />
1<br />
1<br />
1<br />
1<br />
1<br />
Formic acid (5 drops)<br />
Acetic acid (5 drops)<br />
Oxalic acid (0.1 g)<br />
Benzoic acid (0.1 g)<br />
None (= blank test)<br />
Gently shake <strong>and</strong> place the tubes in water bath for 1 min <strong>and</strong> compare with the<br />
blank test. Record your observation.<br />
Caution: Extreme care must be exercised to avoid contact with concentrated sulfuric<br />
acid (safely goggles must be worn at all times). If it comes in contact with the skin or<br />
clothes, it must be washed <strong>of</strong>f immediately with excess water. In addition, sodium<br />
bicarbonate may be used to neutralize the acid. Clean up all spills immediately.<br />
Reference<br />
1. “Introduction to Organic Laboratory Techniques: A Small Scale Approach”, Pavia,<br />
Lampman, Kriz <strong>and</strong> Engel, Brooks/Cole, 2 nd Ed, 2005.<br />
2. “Theory <strong>and</strong> Practice in the Organic Laboratory” L<strong>and</strong>grebe, Brooks/Cole, 5 th Ed,<br />
2005.<br />
3. “Microscale <strong>and</strong> Miniscale Organic Chemistry Laboratory Experiments” Sch<strong>of</strong>fstall,<br />
Gaddis, Druelinger, McGraw Hill, 2 nd Ed, 2004.<br />
4. “Organic Chemistry”, Solomon <strong>and</strong> Fryhle, John Wiley & Sons, 8 th Ed, 2004.<br />
- 38 -
Experiment<br />
10<br />
Oxidation <strong>and</strong> Reduction <strong>of</strong> Benzoin<br />
by Sumrit Wacharasindhu<br />
Objectives<br />
1) To underst<strong>and</strong> oxidation-reduction processes in organic reactions.<br />
2) To perform simple oxidation <strong>and</strong> reduction reactions <strong>of</strong> benzoin <strong>and</strong> related<br />
techniques in laboratory-scale synthesis.<br />
Principles<br />
Focusing on the functional groups in a molecule allows us to recognize patterns<br />
in the behavior <strong>of</strong> related compounds. Consider what we know about the reaction<br />
between sodium metal <strong>and</strong> water, for example;<br />
2 Na(s) + 2 H 2 O(l) H 2 (g) + 2 Na + (aq) + 2 OH - (aq)<br />
We can divide this reaction into two half-reactions. One involves the oxidation <strong>of</strong> sodium<br />
metal to form sodium ions.<br />
Oxidation: Na Na + + e -<br />
The other involves the reduction <strong>of</strong> an H + ion in water to form a neutral hydrogen atom<br />
that combines with another hydrogen atom to form an H 2 molecule.<br />
Reduction:<br />
2<br />
O<br />
H H H + OH<br />
2H 2e 2H H 2<br />
Once we recognize that water contains an -OH functional group, we can predict what<br />
might happen when sodium metal reacts with an alcohol that contains the same<br />
functional group. Sodium metal should react with methanol (CH 3 OH), for example, to<br />
give H 2 gas <strong>and</strong> a solution <strong>of</strong> the Na + <strong>and</strong> CH 3 O - ions dissolved in this alcohol.<br />
2 Na(s) + 2 CH 3 OH(l) H 2 (g) + 2 Na + (alc) + 2 CH 3 O - (alc)<br />
Because they involve the transfer <strong>of</strong> electrons, the reactions between sodium metal <strong>and</strong><br />
either water or alcohol are examples <strong>of</strong> oxidation-reduction. But what about the<br />
following reaction, in which hydrogen gas reacts with an alkene in the presence <strong>of</strong> a<br />
transition metal catalyst to form an alkane<br />
- 39 -
H H H H<br />
Ni<br />
C C + H 2 H C C<br />
H H<br />
H H<br />
H<br />
There is no change in the number <strong>of</strong> valence electrons on any <strong>of</strong> the atoms in this<br />
reaction. Both before <strong>and</strong> after the reaction, each carbon atom shares a total <strong>of</strong> eight<br />
valence electrons <strong>and</strong> each hydrogen atom shares two electrons. Instead <strong>of</strong> electrons,<br />
this reaction involves the transfer <strong>of</strong> atoms in this case, hydrogen atoms. There are<br />
so many atom-transfer reactions that chemists developed the concept <strong>of</strong> oxidation<br />
number to extend the idea <strong>of</strong> oxidation <strong>and</strong> reduction to reactions in which electrons<br />
aren't necessarily gained or lost.<br />
Oxidation involves an increase in the oxidation number <strong>of</strong> an atom.<br />
Reduction occurs when the oxidation number <strong>of</strong> an atom decreases.<br />
During the transformation <strong>of</strong> ethene into ethane, there is a decrease in the oxidation<br />
number <strong>of</strong> the carbon atom. This reaction therefore involves the reduction <strong>of</strong> ethene to<br />
ethane.<br />
-2<br />
H H H H<br />
Ni<br />
C C + H 2 H C C<br />
H H<br />
H H<br />
-3<br />
H<br />
Reactions in which none <strong>of</strong> the atoms undergo a change in oxidation number are called<br />
metathesis reactions. Consider the reaction between a carboxylic acid <strong>and</strong> an amine,<br />
for example.<br />
CH 3 CO 2 H + CH 3 NH 2 CH 3 CO 2 + CH 3 NH 3<br />
Or the reaction between an alcohol <strong>and</strong> hydrogen bromide.<br />
CH 3 CH 2 OH + HBr CH 3 CH 2 Br + H 2 O<br />
These are metathesis reactions because there is no change in the oxidation number <strong>of</strong><br />
any atom in either reaction. The oxidation numbers <strong>of</strong> the carbon atoms in a variety <strong>of</strong><br />
compounds are given in the following table.<br />
- 40 -
Typical Oxidation Numbers <strong>of</strong> Carbon<br />
Functional Group Example<br />
Oxidation Number <strong>of</strong><br />
Carbon in the Example<br />
Alkane CH 4 -4<br />
Alkyllithium CH 3 Li -4<br />
Alkene H 2 C=CH 2 -2<br />
Alcohol CH 3 OH -2<br />
Ether CH 3 OCH 3 -2<br />
Alkyl halide CH 3 Cl -2<br />
Amine CH 3 NH 2 -2<br />
Alkyne HC CH -1<br />
Formaldehyde H 2 CO 0<br />
Aldehyde RCHO +1<br />
Carboxylic acid RCO 2 H +3<br />
Carbon dioxide CO 2 +4<br />
In this experiment, benzoin having both a secondary alcohol <strong>and</strong> a ketone<br />
functional group can be oxidized to a diketone, benzil, or reduced to a diol, hydrobenzoin.<br />
In this reaction, the commonly used reducing agent, sodium borohydride, is used for the<br />
reduction. The oxidation can be accomplished with any <strong>of</strong> several oxidizing agents, such<br />
as nitric acid.<br />
O<br />
OH<br />
HNO 3<br />
Benzoin<br />
NaBH 4<br />
MW 212.24<br />
O<br />
OH<br />
O<br />
Benzil<br />
MW 210.23<br />
OH<br />
Hydrobenzoin<br />
MW 214.26<br />
- 41 -
Experimental Procedure<br />
Part I Oxidation <strong>of</strong> benzoin to benzil (step 1-3 must be carried out in fume hood)<br />
1. Place 1.0 g <strong>of</strong> benzoin into a 50 mL Erlenmeyer flask <strong>and</strong> carefully add 7 mL <strong>of</strong><br />
concentrated nitric acid.<br />
2. Heat the mixture on a steam bath with occasional slow swirling for 30 min or until the<br />
brown-red nitric oxide gas longer evolves. Make sure that the fume hood safety<br />
shield is pulled down.<br />
Caution: Concentrated nitric acid is highly corrosive <strong>and</strong> can cause severe burns.<br />
Nitric oxide (NO 2 ) fume is highly toxic <strong>and</strong> can damage the lungs.<br />
3. Pour the reaction mixture into 25 mL <strong>of</strong> cool water <strong>and</strong> stir to coagulate the<br />
precipitated product.<br />
4. Collect the yellow solid by suction filtration <strong>and</strong> wash the precipitate twice with 5 mL<br />
<strong>of</strong> cool water to remove trace amount <strong>of</strong> nitric acid.<br />
5. Air dry the product on the filtration set for 1 min <strong>and</strong> transfer it onto a watch glass.<br />
6. Remove trace amount <strong>of</strong> water in the product by placing another piece <strong>of</strong> dry filter<br />
paper over <strong>and</strong> pressing with the bottom <strong>of</strong> a small beaker or round-bottom flask.<br />
7. Recrystallize the product by adding 5 mL <strong>of</strong> 95% ethanol, heating the mixture in the<br />
steam bath to make a clear solution, <strong>and</strong> adding water dropwise until cloudiness<br />
occurs. Allow the solution to cool to room temperature <strong>and</strong> then place in an ice bath.<br />
8. Collect the yellow solid by suction filtration.<br />
9. Air dry the product on the filtration set for 1 min <strong>and</strong> transfer onto a watch glass.<br />
10. Weigh the product, record the yield, <strong>and</strong> determine the melting point.<br />
Part II Reduction <strong>of</strong> benzoin to hydrobenzoin<br />
1. Place 1.0 g <strong>of</strong> benzoin into a 50 mL Erlenmeyer flask <strong>and</strong> dissolve it with 10 mL <strong>of</strong><br />
95% ethanol.<br />
2. Carefully add, in small portions, over 5 minutes, 0.20 g <strong>of</strong> sodium borohydride while<br />
swirling. This reaction is exothermic. Do not add sodium borohydride too rapidly.<br />
3. Allow the reaction to proceed at room temperature for 20 min with frequent swirling.<br />
4. Cool the reaction in an ice bath, add 15 mL <strong>of</strong> water, then 0.5 mL <strong>of</strong> 6 M HCl.<br />
5. Add another 5 mL <strong>of</strong> water <strong>and</strong> allow the mixture to st<strong>and</strong> for 20 min at room<br />
temperature with frequent swirling.<br />
6. Collect the product by suction filtration <strong>and</strong> rinse with 50 mL <strong>of</strong> water.<br />
7. Recrystallize the product by adding 5 mL <strong>of</strong> 95% ethanol, heating the mixture in the<br />
steam bath to make a clear solution, <strong>and</strong> adding water dropwise until cloudiness<br />
occurs. Allow the solution to cool to room temperature <strong>and</strong> then place in an ice bath.<br />
8. Collect the yellow solid by suction filtration.<br />
9. Air dry the product on the filtration set for 1 min <strong>and</strong> transfer onto a watch glass.<br />
10. Weigh the product, record the yield <strong>and</strong> determine the melting point.<br />
- 42 -
Experiment<br />
11<br />
Amines<br />
by Duangamol Nuntasri<br />
Objectives<br />
1. To classify amines according to their characteristic chemical reactions<br />
2. To use the chemical characteristics to identify amine sample<br />
Principles<br />
Amines are organic compounds that resemble ammonia but at least one hydrogen<br />
atom is replaced by organic substituents like alkyl (alkane chain) <strong>and</strong> aryl (aromatic<br />
ring) groups.<br />
Types <strong>of</strong> Amines<br />
Amines can be classified as primary, secondary or tertiary. If there is only one carboncontaining<br />
group (such as in CH 3 NH 2 ) then it is considered primary. Two carboncontaining<br />
groups make it secondary, <strong>and</strong> three groups make it tertiary. The lone pair <strong>of</strong><br />
electrons on the nitrogen is sometimes donated to form a fourth carbon-containing<br />
group to the amine. In this case, quaternary ammonium salt (R 4 N + X - ) is obtained.<br />
Primary amine Secondary amine Tertiary amine<br />
H<br />
N<br />
R 1<br />
H<br />
N<br />
R 1<br />
R 1<br />
R 3 N<br />
H<br />
R 2<br />
R 2<br />
An organic compound with multiple amine groups is called a diamine, triamine,<br />
tetraamine <strong>and</strong> so forth, based on the number <strong>of</strong> amino groups on the molecule. The<br />
formula for the simplest diamine, for example, is<br />
Aromatic amines<br />
H 2 N-CH 2 -NH 2<br />
Aromatic amines have the nitrogen atom directly bonded to an aromatic ring. Due to its<br />
delocalization properties, the aromatic ring greatly decreases the basicity <strong>of</strong> the amine -<br />
this effect can be either enhanced or <strong>of</strong>fset depending on the substituents on the ring<br />
<strong>and</strong> on nitrogen. The presence <strong>of</strong> the lone pair electrons from the nitrogen has an<br />
opposite effect on the electron density <strong>of</strong> the ring. It causes the ring to become much<br />
more reactive, particularly towards electrophiles.<br />
- 43 -
Naming conventions<br />
Generally amines are named for their carbon structures with the amine functionality<br />
included as either a prefix (amino-) or a suffix (-amine"). Generally, smaller molecules<br />
will use the suffix form, while larger chains will list amine functionality as if it were any<br />
other type <strong>of</strong> functional group. Examples include methlyamine (CH 3 NH 2 ), <strong>and</strong> 2-<br />
aminopentane (CH 3 NH 2 CH(CH 2 ) 2 CH 3 ).<br />
• as prefix: "amino-"<br />
• as suffix: "-amine"<br />
• the prefix "N-" shows substitution on the nitrogen atom (in the case <strong>of</strong> secondary,<br />
tertiary <strong>and</strong> quaternary amines)<br />
Systematic names for some common amines:<br />
small amines are named<br />
with the suffix -amine.<br />
large amines have the prefix<br />
amino as a functional group.<br />
H 3 C CH 3<br />
H 2 N CH 3 NH 2<br />
Methylamine<br />
2-Aminopentane<br />
Physical properties<br />
1. Basicity<br />
1.1 Solubility <strong>and</strong> 1.2 Indicator testing<br />
All three classes <strong>of</strong> amines form hydrogen bonds with water.<br />
N + H OH<br />
N H OH<br />
For this reason, low-molecular weight amines are water soluble. Borderline water<br />
solubility is observed when the amine has about six carbon atoms. Aqueous solutions <strong>of</strong><br />
amines are alkaline (basic).<br />
N<br />
H OH<br />
N H + OH<br />
Like ammonia, amines act as reasonably strong bases (see the provided table for some<br />
examples <strong>of</strong> conjugate acid K a values). The basicity <strong>of</strong> amines varies by molecule, <strong>and</strong><br />
it largely depends on:<br />
• The availability <strong>of</strong> the lone pair electrons on the nitrogen<br />
- 44 -
Ions <strong>of</strong> compound<br />
K b<br />
ammonia NH 3 1.8 × 10 -5<br />
methylamine CH 3 NH 2 4.4 × 10 -4<br />
propylamine CH 3 CH 2 CH 2 NH 2 4.7 × 10 -4<br />
2-propylamine (CH 3 ) 2 CHNH 2 5.3 × 10 -4<br />
diethylamine (CH 3 ) 2 NH 2 9.6 × 10 -4<br />
+I inductive effect <strong>of</strong> alkyl groups raises the energy <strong>of</strong> the lone pair <strong>of</strong> electrons, thus<br />
elevating the basicity.<br />
• The electronic properties <strong>of</strong> the attached substituent groups (e.g., alkyl groups<br />
enhance the basicity, aryl groups diminish it, etc.)<br />
Ions <strong>of</strong> compound<br />
K b<br />
ammonia NH 3 1.8 × 10 -5<br />
aniline C 6 H 5 NH 2 3.8 × 10 -10<br />
4-methylphenylamine 4-<br />
CH 3 C 6 H 4 NH 2<br />
1.2 × 10 -9<br />
+M mesomeric effect <strong>of</strong> aromatic ring delocalizes the lone pair electron into the ring,<br />
resulting in decreased basicity.<br />
• The degree <strong>of</strong> solvation <strong>of</strong> the protonated amine, which depends mostly on the<br />
solvent used in the reaction<br />
The nitrogen atom <strong>of</strong> a typical amine features a lone electron pair which can bind a<br />
hydrogen ion (H + ) in order to form an ammonium ion -- R 3 NH + . The water solubility <strong>of</strong><br />
simple amines is largely due to the extent <strong>of</strong> hydrogen bonding that occurs between<br />
protons <strong>of</strong> water <strong>and</strong> N lone pairs.<br />
Amine protonation VS water solubility:<br />
Ions <strong>of</strong> compound<br />
NH 4<br />
+<br />
+<br />
RNH 3<br />
+<br />
R 2 NH 2<br />
R 3 NH +<br />
Maximum number <strong>of</strong> H-bond<br />
4 Very Soluble in H 2 O<br />
3<br />
2<br />
1 Least Soluble in H 2 O<br />
- 45 -
1.3 Salt Formation<br />
Amines are weak organic bases that form salts with strong acids.<br />
N + H + Cl - N H Cl<br />
Like ordinary salts, ammonium salts are readily dissociate into ions <strong>and</strong> are therefore<br />
water soluble. The salts can be reconverted to amines by making their solutions<br />
alkaline.<br />
N H Cl + Na + OH - N + Na + Cl - + H 2 O<br />
2. Reaction with bromine in water<br />
The amino functional group in aniline works as electron donating group to the benzene<br />
ring via resonance effect, making electrophilic aromatic substitution reaction more<br />
favorable than for non-substituted aromatics. For the bromination <strong>of</strong> aniline, bromine<br />
acts as electrophile which gets directed to substitute hydrogen atoms at ortho- <strong>and</strong><br />
para- positions, producing 2-4-6-tribromoaniline. With, aliphatic amines this type <strong>of</strong><br />
reaction cannot occur.<br />
NH 2<br />
+ 3 Br 2<br />
NH 2<br />
Br<br />
Br<br />
+ 3 HBr<br />
3. Reaction with nitrous acid<br />
Nitrous acid (HNO 2 ) is unstable, <strong>and</strong> so a mixture <strong>of</strong> NaNO 2 <strong>and</strong> dilute acid is usually<br />
used to produce nitrous acid in situ. Primary aliphatic amines with nitrous acid give very<br />
unstable diazonium salts which spontaneously decompose by losing N 2 gas, forming a<br />
carbonium ion. The carbonium ion goes on to produce a mixture <strong>of</strong> alkenes, alcohols or<br />
alkyl halides, with alcohols as the major product. This reaction is <strong>of</strong> little synthetic<br />
importance because the diazonium salt formed is too unstable, even under quite cold<br />
conditions.<br />
NaNO 2 + HCl → HNO 2 + NaCl<br />
Br<br />
R<br />
H 2 C NH 2<br />
HCl<br />
NaNO 2<br />
R<br />
C<br />
H 2<br />
N<br />
N<br />
R CH 2 + N N H 2 C OH<br />
R<br />
Primary aromatic amines, such as aniline (phenylamine) form a more stable diazonium<br />
ion at 0–5°C. Above 5°C, it decomposes to give phenol <strong>and</strong> N 2 . Diazonium salts can be<br />
isolated in the crystalline form but are usually used in solution <strong>and</strong> immediately after<br />
preparation, due to rapid decomposition on st<strong>and</strong>ing even with little ambient heat. Solid<br />
diazonium salts can be explosive on mild warming.<br />
- 46 -
NH 2<br />
HCl / NaNO 2<br />
5 o C<br />
N<br />
N<br />
If the primary amine is readily converted to a diazonium salt <strong>and</strong> loses nitrogen, bubbles<br />
will be visible in a very short period <strong>of</strong> time. If no bubbles <strong>of</strong> nitrogen appear, you can<br />
assume that the amine is secondary or tertiary rather than primary.<br />
At low temperatures, diazonium salts are stable <strong>and</strong> will couple with the alpha position<br />
with the sodium salt <strong>of</strong> β-naphthol to form a red colored precipitates.<br />
Cl<br />
N<br />
N<br />
+<br />
OH<br />
OH<br />
N<br />
N<br />
β-naphthol<br />
(colorless)<br />
Azo compound<br />
(red)<br />
4. Hinsberg test<br />
The reaction between primary or secondary amines <strong>and</strong> benzenesulfonyl chloride in the<br />
presence <strong>of</strong> sodium hydroxide solution yields the corresponding substituted<br />
benzenesulfonamide, whereas tertiary amines do not react with this combination <strong>of</strong><br />
reagents.<br />
With primary amines the sulfonamide formed is acidic <strong>and</strong> dissolves in the excess base<br />
used to yield a solution <strong>of</strong> the corresponding anion. Addition <strong>of</strong> excess hydrochloric acid<br />
converts the anion into the water-insoluble sulfonamide.<br />
NaOH<br />
RNH 2 + SO 2 Cl SO 2 NHR<br />
+ NaCl + H 2 O<br />
Insoluble in water<br />
excess<br />
HCl<br />
excess<br />
NaOH<br />
SO 2 NRNa + H 2 O<br />
Solubility in water<br />
Secondary amines react with benzenesulfonyl chloride but the sulfonamide lacks an<br />
amide hydrogen <strong>and</strong> is insoluble in the both aqueous basic <strong>and</strong> acid reagents.<br />
- 47 -
R 2 NH<br />
NaOH<br />
+ SO 2 Cl SO 2 NR 2<br />
+ NaCl + H 2 O<br />
Insoluble in water<br />
excess<br />
NaOH<br />
No reaction<br />
Tertiary amines react differently with benzenesulfonyl chloride; the intermediate<br />
ammonium ion does not have a proton to lose <strong>and</strong> reacts rapidly with hydroxide ion to<br />
displace the benzenesulfonate anion <strong>and</strong> regenerate the tertiary amine.<br />
NaOH<br />
R 3 N + SO 2 Cl SO 2 NR 3 Cl<br />
water soluble<br />
excess<br />
NaOH<br />
SO 3 + NR 3 + Cl<br />
water soluble<br />
The overall reaction amounts to an amine-catalyzed hydrolysis <strong>of</strong> the benzenesulfonyl<br />
chloride. With tertiary amines there can be a side reaction between the amine <strong>and</strong> the<br />
intermediate ammonium ion to produce a complex mixture <strong>of</strong> water-insoluble products,<br />
which could lead to confusion with the results for a secondary amine. This complication<br />
can be minimized by keeping the concentration <strong>of</strong> the amine low. If there is any doubt<br />
regarding the interpretation <strong>of</strong> the results, carry out the test on known compounds <strong>and</strong><br />
compare the results with those <strong>of</strong> the unknown.<br />
5. Rimini’s test, Simon’s test, modified Rimini’s test <strong>and</strong> modified Simon’s test<br />
Rimini’s reagent (sodium nitroprusside <strong>and</strong> acetone) <strong>and</strong> Simon’s reagent (sodium<br />
nitroprusside <strong>and</strong> acetaldehyde) can be used as to distinguish primary amines from<br />
secondary aliphatic ones. When amines react with Rimini’s reagent, different colors are<br />
produced, according to Table 1. Modified versions <strong>of</strong> Rimini’s reagent <strong>and</strong> Simon’s<br />
reagent, however work well for identifying aryl amines. i.e. primary, secondary <strong>and</strong><br />
tertiary aromatic amines.<br />
- 48 -
Table 1 The developed color <strong>of</strong> Rimini’s test, Simon’s test, modified Rimini’s test <strong>and</strong><br />
modified Simon’s test<br />
Reagent 1 o aliphatic 2 o aliphatic 1 o aromatic 2 o aromatic 3 o aromatic<br />
Rimini purple deep red - - -<br />
Simon<br />
Modified<br />
Rimini<br />
Modified<br />
Simon<br />
pale yellow<br />
to<br />
red brown<br />
- -<br />
- -<br />
deep blue - - -<br />
orange red<br />
to<br />
red brown<br />
orange red<br />
to<br />
red brown<br />
Blue green<br />
purple<br />
blue green<br />
blue green<br />
Amine samples for chemical reaction testing<br />
Aliphatic amine<br />
C 4 H 7<br />
C 4 H 7 NH 2<br />
C 4 H 7 NH<br />
n-butylamine<br />
di-n-butylamine<br />
Aromatic amine<br />
NH 2<br />
CH 3<br />
NH<br />
CH 3<br />
N CH 3<br />
Aniline N-methylaniline N,N-dimethylaniline<br />
- 49 -
Experimental Procedure<br />
1. Basicity testing<br />
1.1 Water solubility<br />
Test with n-butylamine, di-n-butylamine <strong>and</strong> N,N-dimethylaniline<br />
To 2 mL <strong>of</strong> distilled water in a test tube, add 5 drops <strong>of</strong> amine <strong>and</strong> note its solubility.<br />
Test the resulting solution with pink litmus paper.<br />
1.2 Indicator test<br />
Test with n-butylamine <strong>and</strong> aniline<br />
Add 2 drops <strong>of</strong> amine to each <strong>of</strong> two test tubes containing 1 ml <strong>of</strong> distilled water. To one<br />
tube add a drop <strong>of</strong> phenolphthalein indicator <strong>and</strong> to the other add a drop <strong>of</strong><br />
bromothymol blue solution. Interpret the results observed on the basis <strong>of</strong> the following<br />
information: bromothymol blue; below pH 6 the color is yellow, at pH 7 it is yellow-green,<br />
<strong>and</strong> above pH 7.5 the color is blue. Phenolphthalein is colorless at pH 8.4 <strong>and</strong> red<br />
above pH 8.6.<br />
1.3 Salt formation<br />
Test with n-butylamine <strong>and</strong> aniline<br />
To 10 drops <strong>of</strong> 6M HCl, add 2 drops <strong>of</strong> amine <strong>and</strong> shake. Note whether the amine is<br />
soluble in aquous acid. Add 6M NaOH dropwise until the solution becomes alkaline, <strong>and</strong><br />
observe.<br />
2. Reaction with bromine in water<br />
Test with n-butylamine <strong>and</strong> aniline<br />
To 1 ml <strong>of</strong> distilled water in test tubes, add 1 drop <strong>of</strong> amine then bromine water<br />
dropwise until excess <strong>of</strong> bromine <strong>and</strong> shake.<br />
3. Reaction with nitrous acid (Azo dye)<br />
Test with n-butylamine <strong>and</strong> aniline<br />
To 1 mL <strong>of</strong> conc. HCl <strong>and</strong> 1mL <strong>of</strong> water, add amine 5 drops. Stir the solution while<br />
cooling in ice bath (ensure temperature does not exceed 5 o C). Dissolve 0.2 g NaNO 2 in<br />
1 mL distilled water <strong>and</strong> cool in ice bath at the same temperature. Add NaNO 2 solution<br />
dropwise with stirring or shaking to the cold amine hydrochloride. The endpoint can be<br />
determined by putting a drop <strong>of</strong> the solution on starch-KI paper. A blue color is observed<br />
when excess nitrite is present. Observe whether bubbles appear or not.<br />
Compare the result between n-butylamine <strong>and</strong> aniline.<br />
Remove about 1 mL <strong>of</strong> the aniline diazonium chloride solution into test tube <strong>and</strong> heat on<br />
water bath at 50 o C. Observe the change <strong>and</strong> odour.<br />
To another portion <strong>of</strong> the cold aniline diazonium solution, add a pre-chilled solution <strong>of</strong><br />
0.1 g <strong>of</strong> β-naphthol in 1 mL <strong>of</strong> 5% NaOH. Observe the result.<br />
- 50 -
4. Hinsberg Test<br />
Test with aniline, N-methylaniline <strong>and</strong> N,N-dimethylaniline<br />
To 2 drops <strong>of</strong> amine in test tube with 1 mL <strong>of</strong> water, add 1 mL <strong>of</strong> 10% aqueous NaOH<br />
<strong>and</strong> 2 drops <strong>of</strong> benzenesulfonyl chloride (in hood). Close test tube tightly with stopcock<br />
<strong>and</strong> vigorously shake the tube for 5 mins <strong>and</strong> note any reaction. If unreacted<br />
benzenesulfonyl chloride is left as an oil drop at bottom <strong>of</strong> tube. In this case, warm the<br />
mixture do not boil in hood with shaking for 10 min. The reaction mixture should still be<br />
strongly alkaline at this point. Cool the test tube to room temperature, shake well, <strong>and</strong><br />
note whether any solid or liquid separates. Do not confuse any separated material with<br />
unreacted benzenesulfonyl chloride. Observe the result.<br />
Separate half amount <strong>of</strong> reaction mixture (both liquid <strong>and</strong> solid) into new test tube. Add<br />
2M <strong>of</strong> HCl until solution turns acidic. Observe if a precipitate forms. If so, this indicates<br />
that the unknown was a primary amine. However, if the organic material does not<br />
dissolve in the hydrochloric acid, it indicates a secondary amine (acid- <strong>and</strong> baseinsoluble<br />
secondary sulfonamide). If the organic material is soluble, it indicates a tertiary<br />
amine (acid soluble, unreactive toward benzenesufonyl chloride).<br />
5. Rimini test, Simon test, modified Rimini test <strong>and</strong> modified Simon test<br />
5.1 <strong>and</strong> 5.2 test with aliphatic amine (n-butylamine <strong>and</strong> di-n-butylamine)<br />
5.3 <strong>and</strong> 5.4 test with aromatic amine (aniline, N-methylaniline <strong>and</strong> N,N-dimethylaniline)<br />
5.1 Rimini test<br />
To 1 mL <strong>of</strong> sodium nitroprusside reagent A (0.13 M in 50% aq. methanol) in test tube<br />
with 1 mL <strong>of</strong> water, add 5 drops <strong>of</strong> acetone <strong>and</strong> 3 drops <strong>of</strong> amine. Shake the tube <strong>and</strong><br />
observe result within 2 min.<br />
5.2 Simon test<br />
To 1 mL <strong>of</strong> sodium nitroprusside reagent A (0.13 M in 50% aq. methanol) in test tube<br />
with 1 mL <strong>of</strong> water, add 5 drops <strong>of</strong> 2.5 M acetaldehyde solution <strong>and</strong> 3 drops <strong>of</strong> amine.<br />
Shake the tube <strong>and</strong> observe result within 2 min.<br />
5.3 Modified Rimini test<br />
To 1 mL <strong>of</strong> sodium nitroprusside reagent B (0.13 M in 80% aq. dimethyl sulfoxide) in<br />
test tube with 1 mL <strong>of</strong> saturated ZnCl 2 aqueous solution, add 5 drops <strong>of</strong> acetone <strong>and</strong> 3<br />
drops <strong>of</strong> amine. Shake the tube <strong>and</strong> observe result within 2 min.<br />
5.4 Modified Simon test<br />
To 1 mL <strong>of</strong> sodium nitroprusside reagent B (0.13 M in 80% aq. dimethyl sulfoxide) in<br />
test tube with 1 mL <strong>of</strong> saturated ZnCl 2 aqueous solution, add 5 drops <strong>of</strong> 2.5 M<br />
acetaldehyde solution <strong>and</strong> 3 drops <strong>of</strong> amine. Shake the tube <strong>and</strong> observe result within 2<br />
min.<br />
6. Classification test for an unknown compound<br />
Obtain an unknown sample from your instructor. Record the sample number. First,<br />
determine if the unknown is an alkyl or aryl amine <strong>and</strong> then determine whether the<br />
amine is primary, secondary, or tertiary. Consult with your instructor <strong>and</strong> write down the<br />
answer in your report sheet.<br />
Caution<br />
- Carefully dispose the red azo compound <strong>and</strong> reaction mixture from reaction with<br />
nitrous acid by washing down the drain without contact to your skin.<br />
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Experiment<br />
12<br />
Identification <strong>of</strong> Organic Compounds<br />
by Duangamol Nuntasri<br />
<strong>and</strong> Paitoon Rashatasakhon<br />
Objectives<br />
1. To classify organic compounds to the corresponding solubility classes.<br />
2. To determine functional groups <strong>of</strong> organic compounds by chemical tests<br />
Principles<br />
Qualitative organic analysis, the identification <strong>and</strong> characterization <strong>of</strong> organic<br />
compounds, is an important part <strong>of</strong> organic chemistry. In this experiment you will be<br />
issued an unknown compound <strong>and</strong> asked to identify it through chemical methods. Your<br />
instructor will give you an unknown, you must first determine the class <strong>of</strong> compound to<br />
which the unknown belongs. Then identify its main functional group <strong>and</strong> determine the<br />
specific compound in the class that corresponds to the unknown. Unknown compounds<br />
are restricted to include only eight possible important functional groups: aldehydeketone,<br />
carboxylic acid, phenol, amine, alcohol, alkyl halide, unsaturated, <strong>and</strong><br />
ester. The experiment presents all <strong>of</strong> the chemical methods <strong>of</strong> determining the main<br />
functional groups, <strong>and</strong> it includes methods for verifying the presence <strong>of</strong> the subsidiary<br />
functional groups as well.<br />
How to proceed<br />
1. Preliminary classification by physical state.<br />
2. <strong>Determination</strong> <strong>of</strong> solubility in different solvents<br />
3. Application <strong>of</strong> relevant chemical classification tests<br />
Preliminary classification<br />
Note the physical characteristics <strong>of</strong> the unknown. These include its color, its<br />
odor, <strong>and</strong> its physical state (liquid, solid, crystalline form). Compounds with a high<br />
extent <strong>of</strong> conjugation are frequently yellow to red. Amines <strong>of</strong>ten have a fishlike odor.<br />
Esters have a pleasant fruity or floral odor. Acids have a sharp <strong>and</strong> pungent odor. As a<br />
note <strong>of</strong> caution, many compounds have distinctly unpleasant or nauseating odors.<br />
Some have corrosive vapors. Any unknown substance should be smelled with the<br />
greatest caution. Initially, open the unknown container, holding it away from you. Then,<br />
using your h<strong>and</strong>, carefully waft the vapors toward your nose.<br />
Solubility behavior<br />
Solubility tests are important in determining the nature <strong>of</strong> the main functional<br />
group <strong>of</strong> the unknown compound. These a tests are simple, require only small amounts<br />
<strong>of</strong> unknown, <strong>and</strong> can reveal whether the compound is a base (amine), an acid (phenol),<br />
a stronger acid (carboxylic acid), or a neutral substance (aldehyde, ketone, alcohol,<br />
ester). Common solvents used to determine solubility include water, 5% NaOH, 5%<br />
NaHCO 3 , 5% HCl, <strong>and</strong> conc. H 2 SO 4 .<br />
- 52 -
The solubility tests <strong>and</strong> solubility classes (Table 1) provides a useful <strong>and</strong> logical<br />
approach to determining compound class from solubility observations. The possible<br />
functional groups for each solubility class are listed in Table 2.<br />
Chemical classification tests<br />
The solubility tests usually suggest or eliminate several possible functional<br />
groups. The chemical classification tests listed in Table 3 allows one to distinguish<br />
among these possible choices. You should choose to perform only those meaningful<br />
tests; time is wasted doing unnecessary tests. The solubility <strong>and</strong> the main chemical<br />
tests will be possible to identify the class <strong>of</strong> compound. Solubility tests automatically<br />
eliminate the need for some <strong>of</strong> the chemical tests. Each successive test will either<br />
eliminate the need for another test or dictate its use. Many possibilities may be<br />
eliminated on the basis <strong>of</strong> logic alone.<br />
Experimental Procedure<br />
Part 1 Solubility tests<br />
Five unknowns (A to E) will be used for this experiment. The order <strong>of</strong> solvents for<br />
this test should be as follows:<br />
Water 5% NaOH 5% NaHCO 3 5% HCl concentrated H 2 SO 4<br />
Place about 1 mL <strong>of</strong> the solvent in a test tube. Add two drop or 50 mg (about the<br />
size <strong>of</strong> one grain <strong>of</strong> rice) <strong>of</strong> an unknown directly into solvent. Shake the test tube to<br />
ensure good mixing, <strong>and</strong> then observe whether the unknown is soluble. The<br />
disappearance <strong>of</strong> the liquid or solid, or the appearance <strong>of</strong> the mixing lines, indicates that<br />
dissolution is taking place. Add several more drops <strong>of</strong> the liquid, or a few more crystals<br />
<strong>of</strong> the solid, to determine the extent <strong>of</strong> the compound’s solubility. A common mistake in<br />
determining the solubility <strong>of</strong> a compound is testing with a quantity <strong>of</strong> the unknown too<br />
large to dissolve in the chosen solvent. Use small amounts. It may take several minutes<br />
to dissolve solids. Compounds in the form <strong>of</strong> large crystals will need more time to<br />
dissolve than powders or very small crystals. In some cases it is helpful to first pulverize<br />
a compound composed <strong>of</strong> large crystals. Sometime gentle heating helps, but strong<br />
heating is discouraged, as it <strong>of</strong>ten leads to reaction. When colored compounds dissolve,<br />
the solution <strong>of</strong>ten assumes the same color.<br />
By the above procedure, the solubility <strong>of</strong> the unknown should be determined in<br />
each <strong>of</strong> the following solvents: water, 5% NaOH, 5% NaHCO 3 , 5% HCl, <strong>and</strong><br />
concentrated H 2 SO 4 . With sulfuric acid, a color change may be observed rather than<br />
dissolution. A color change should be regarded as a positive solubility test.<br />
If compound is found to dissolve in water, the pH <strong>of</strong> the aqueous solution should<br />
be estimated with pH paper or litmus. Compounds soluble in water are usually soluble<br />
in all the aqueous solvents. If a compound is only slightly soluble in water, it may be<br />
more soluble in acid or alkali. For instance, a carboxylic acid may be only slightly<br />
soluble in water but very soluble in dilute base. It will <strong>of</strong>ten not be necessary to<br />
determine the solubility <strong>of</strong> the unknown in every solvent.<br />
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Part 2 Solubility test <strong>and</strong> determine functional group <strong>of</strong> specific unknown<br />
- Obtain your specific unknown from the instructor<br />
- Record the unknown number<br />
- Report the physical character <strong>of</strong> the unknown<br />
- Classify unknown into the solubility class, <strong>and</strong> check your answer before<br />
proceed to the next step<br />
- Examine unknown functional group using appropriate chemical tests as shown in<br />
Table 3<br />
- Report the answer <strong>of</strong> unknown in your report sheet<br />
Ref. Pavia, D.L.; Lampman, G.L.; Kriz, G.S. Introduction to Organic Laboratory<br />
Techniques, 3 rd ed., W.B. Saunders Company, New York.<br />
- 54 -
Table 1<br />
Solubility tests <strong>and</strong> Solubility classes<br />
Water<br />
Soluble <strong>and</strong><br />
change blue<br />
litmus into red<br />
Soluble but does<br />
not change blue<br />
litmus into red<br />
Soluble <strong>and</strong><br />
change red<br />
litmus into blue<br />
Soluble but does<br />
not change red<br />
litmus into blue<br />
Insoluble<br />
Insoluble<br />
Insoluble<br />
Solvent (1 ml) : unknown (2 drops or 1 grain <strong>of</strong> rice)<br />
5%<br />
NaOH<br />
-<br />
-<br />
5%<br />
NaHCO 3<br />
5%<br />
HCl<br />
Produces<br />
CO 2 gas<br />
No gas<br />
evolves<br />
conc.<br />
H 2 SO 4<br />
5%<br />
FeCl 3<br />
- - -<br />
- -<br />
- - - -<br />
- - - -<br />
Soluble<br />
Slightly<br />
soluble<br />
Insoluble<br />
Insoluble Insoluble -<br />
Insoluble Insoluble -<br />
Note 1. “ - ” = unnecessary.<br />
Change color <strong>of</strong><br />
FeCl 3 solution<br />
Produce redbrown<br />
precipitate<br />
Does not change<br />
color <strong>of</strong> FeCl 3<br />
solution<br />
Solubility class<br />
Water soluble strong<br />
acid<br />
Water soluble weak acid<br />
Water soluble base<br />
Water soluble neutral<br />
compound<br />
Slightly<br />
soluble <strong>and</strong><br />
produces<br />
CO 2 gas<br />
- - - Strong acid<br />
Insoluble -<br />
- - Weak acid<br />
-<br />
Soluble<br />
(contains N<br />
atoms)<br />
Insoluble<br />
(contains N or<br />
S atoms)<br />
Insoluble<br />
(no N or S<br />
atom)<br />
- - Basic compound<br />
- -<br />
Miscellaneous neutral<br />
compound<br />
(this class <strong>of</strong> compounds is not<br />
available in this course)<br />
Soluble - Neutral compound<br />
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Table 2<br />
Functional group tests for compounds in each solubility class<br />
Functional groups<br />
Solubility class<br />
Neutral<br />
Carboxylic<br />
Phenol<br />
(see note 1)<br />
acid<br />
Water soluble strong acid √ √<br />
Water soluble weak acid<br />
√<br />
Water soluble base<br />
Water soluble neutral compound √<br />
Strong acid √ √<br />
Weak acid<br />
√<br />
Basic compound<br />
Neutral compound<br />
√<br />
Amine<br />
Note :<br />
1. The following functional groups are possible for this class <strong>of</strong> compounds.<br />
1.1. carbonyl compounds (aromatic or aliphatic aldehyde, α-hydroxy ketone, methyl ketone,<br />
or other ketone)<br />
1.2. alcohol (primary, secondary, or tertiary alcohol)<br />
1.3. ester<br />
1.4. unsaturated hydrocarbon (alkene or alkyne)<br />
1.5. alkyl halide (primary, secondary, or tertiary alkyl halides)<br />
1.6. nitro compound (not available in this course)<br />
1.7. thiol (not available in this course)<br />
1.8. amide (not available in this course)<br />
1.9. ether (not available in this course)<br />
√<br />
√<br />
The solubility flow-chart below provides a summary <strong>of</strong> information from Table 1 <strong>and</strong> Table 2.<br />
- 56 -
turn red litmus to blue<br />
turn blue litmus to red<br />
low MW<br />
amines<br />
low MW<br />
carboxylic acids<br />
soluble<br />
No change with<br />
litmus<br />
neutral, hydrogen<br />
bonding or neutral but<br />
polar<br />
Unknown<br />
H 2 O<br />
insoluble<br />
5%NaHCO 3<br />
soluble<br />
soluble<br />
insoluble<br />
strong acids<br />
weak acids<br />
carboxylic acids<br />
some phenols<br />
phenols<br />
5%NaOH<br />
insoluble<br />
soluble<br />
bases<br />
amines<br />
5%HCl<br />
insoluble<br />
conc.H 2 SO 4<br />
soluble<br />
insoluble<br />
neutral<br />
compounds<br />
alkenes esters<br />
alkynes ethers<br />
alcohols amides<br />
ketones thiols<br />
aldehydes<br />
alkyl halides<br />
nitro compounds<br />
inert<br />
compounds<br />
alkanes<br />
aromatic<br />
- 57 -
Table 3 Functional group tests <strong>and</strong> required reagents<br />
Functional group Sub-functional group Reagents<br />
(see note 1)<br />
Solvent for solid<br />
unknown<br />
Aldehyde, ketone Aldehyde: aliphatic,aromatic 1. 2,4-DNP Ethanol<br />
(see exp. 8)<br />
2. Schiff’s reagent Ethanol<br />
Alcohol<br />
(see exp. 6)<br />
Ester<br />
(see exp. 9)<br />
Unsaturation<br />
(see exp. 4)<br />
Carboxylic acid<br />
(see exp. 9)<br />
Phenol<br />
(see exp. 6)<br />
Amine<br />
(see exp. 11)<br />
Alkyl halides<br />
(see exp. 5)<br />
Ketone: α-hydroxy ketone,<br />
methyl ketone, other ketones<br />
3. Tollens’ reagent Ethanol<br />
4. Benedict’s reagent Ethanol<br />
5. Iod<strong>of</strong>orm test Ethanol<br />
1°, 2°, 3° alcohol 1. Ceric nitrate reagent<br />
(positive results= red or orange)<br />
2. Lucas reagent<br />
3. Oxidation test<br />
Aliphatic, aromatic amine<br />
1°, 2°, 3° amine<br />
- Ferric hydroxamate test -<br />
- 1. KMnO 4<br />
2. Br 2 /CCl 4<br />
- 5% NaHCO 3 -<br />
-<br />
1. 5% FeCl 3 Ethanol<br />
2. Ceric nitrate reagent Dioxane or acetone<br />
3. Br 2 /H 2 O Ethanol<br />
1. 2 M HCl<br />
2. Sodium Nitroprusside Test<br />
(Ramini, Simon, Modified<br />
Ramini <strong>and</strong> Simon)<br />
3. Diazotization & Coupling<br />
4. Br 2 /H 2 O<br />
1°, 2°, 3° alkyl halide 1. AgNO 3 / EtOH<br />
2. NaI / actone<br />
Note:<br />
1. For liquid unknown, perform the tests without any solvent.<br />
2. For solid unknown which is soluble in water, perform the tests using a solution <strong>of</strong> the<br />
unknown in water.<br />
3. For solid unknown which is insoluble in water, perform the tests using a solution <strong>of</strong> the<br />
unknown in solvent listed in Table 3.<br />
-<br />
-<br />
-<br />
-<br />
- 58 -