10.4 CARBOXYLIC ACIDS ESTERS AND ESTERIFICATION REACTIONS

(b) Methanol and ethanol, having both polar hydroxyl groups and nonpolar carbon chains, 

are soluble in both water and in gasoline; thus water droplets are dissolved in the alcohol 

and do not form ice, which blocks gasoline flow. 

13. (a) 

(b) Ethylene glycol is a better choice as a radiator antifreeze and coolant than ethanol 

because it has a much higher boiling point (197 °C vs 79 °C) due to its stronger London 

forces and hydrogen bonding. A mixture of ethylene glycol and water can be heated to a 

higher temperature before it boils, compared to a mixture of ethanol and water. Ethylene 

glycol also has a larger specific heat capacity than ethanol, which allows for the 

absorption of larger amounts of heat from an engine for the same increase in temperature. 

(c) Methanol, rather than ethanol glycol, is used as a windshield wiper antifreeze for three 

reasons. First, ethylene glycol has a higher melting point (–13 °C vs –97 °C), which 

means it is likely to get too viscous or even freeze at temperatures that can occur during 

winter. Second, ethylene glycol is more viscous than methanol, which could make 

clearing the liquid from the windshield a problem. Spilled or sprayed ethylene glycol, 

with its higher boiling point and lower volatility, evaporates very slowly compared to 

methanol, which evaporates much more quickly. 

(d) According to the Material Safety Data Sheet (MSDS) references, methanol is more toxic 

than ethylene glycol. The lowest reported lethal dose for a human is 428 mg/kg for 

methanol and 786 mg/kg for ethylene glycol. 

(e) A 50:50 dilution of ethylene glycol in water has a freezing point of –37 °C. 

10.4 CARBOXYLIC ACIDS, ESTERS, AND ESTERIFICATION REACTIONS 

Lab Exercise 10.B: Explaining Physical Property Trends 

(Page 437) 

Purpose 

The purpose of this investigation is to use your knowledge of organic structures and 

intermolecular forces to explain some physical properties of alcohols and carboxylic acids. 

Problem 

What is the explanation for the trends in boiling points and solubilities in water within and 

between series of simple alcohols and carboxylic acids? 

Analysis 

The boiling point increase of methanol (65 C) to pentan-1-ol (137 C) can be explained by 

the increase in the size of the molecules and the number of electrons. As the size increases, 

the strength of the London forces increases, which means that the strength between molecules 

increases, which in turn causes an increase in boiling points. The dipole–dipole and hydrogen 

bonding forces should be approximately the same for all the alcohols. 

Copyright © 2007 Thomson Nelson Unit 5 Solutions Manual 365

The decrease in solubility of alcohols in water comes from the addition of CH 2 groups to the 

alcohol. The more CH 2 groups added to the parent chain, the greater the nonpolar portion of 

the alcohol and the less its solubility. 

The boiling point increase of methanoic acid (101 C) to pentanoic acid (186 C) can be 

explained by the increase in the size of the molecules and the number of electrons. As the size 

increases, the strength of the London forces increases, which means that the strength between 

molecules increases, which in turn causes an increase in boiling points. The dipoledipole 

and hydrogen bonding forces should be approximately the same for all the acids. 

The decrease in solubility of carboxylic acids in water comes from the addition of CH 2 

groups to the acid. The more CH 2 groups added to the parent chain, the greater the nonpolar 

portion of the acid and lower its solubility. 

The carboxylic acids as a group have a higher set of boiling points than alcohols and are 

generally more soluble in water. The carboxylic acid group is more polar than the hydroxyl 

group on the alcohol and there are more locations available for hydrogen bonding. 

Evaluation 

The purpose was accomplished because the explanation for trends in boiling points and 

solubilities of alcohols and carboxylic acids seems to be logical and consistent with 

intermolecular theories and rules. There are no exceptions or unexplained results. 

Practice 

(Page 438) 

1. (a) 

(b) 

(c) 

2. (a) methanoic acid (formic acid) 

(b) pentanoic acid 

(c) hexanoic acid 

Practice 

(Pages 441–442) 

[Note that the ester functional group is –COO– and the general formula for an ester is 

R 1 (H)–COO–R 2 .] 

3. (a) rum flavour 

366 Unit 5 Solutions Manual Copyright © 2007 Thomson Nelson

(b) cherry flavour 

(c) apple flavour 

(d) banana flavour 

4. (a) ethyl propanoate (from propanoic acid and ethanol) 

(b) methyl butanoate (from butanoic acid and methanol) 

(c) butyl methanoate (from methanoic acid and butan-1-ol) 

(d) propyl ethanoate (from ethanoic acid and propan-1-ol) 

5. (a) pentan-1-ol and butanoic acid make pentyl butanoate 

(b) octan-1-ol and ethanoic acid make octyl ethanoate 

6. (a) The boiling points of the three classes of straight-chain organic compounds increase as 

the number of CH 2 groups are added to the parent chain. This occurs because as the 

number of electrons increases, the London force increases, increasing the total 

intermolecular forces and increasing the boiling point. Dipole–dipole forces and 

hydrogen bonding (acids) are assumed to be constant within a group. 

(b) At lower molar masses, the esters have slightly higher boiling points than alkanes 

because their molecules are polar with a small additional dipole–dipole force. However, 

as the size of the ester increases, the nonpolar portion of the molecules increases and the 

dipole–dipole forces become a much smaller part of the total intermolecular forces 

present. Since there is no hydrogen bonding, and there are only slight dipole–dipole 

forces, the strength of the intermolecular forces is similar for the same length of parent 

chain. 

(c) Carboxylic acids have higher boiling points than the alkanes or methyl esters of similar 

molar mass because they have additional hydrogen bonding forces, which the alkanes and 

methyl esters do not have. 

(d) The intermolecular force theories pass the test of being able to explain the relative boiling 

points, but an anomaly appears. At approximately 110 g/mol, the alkanes, with no 

dipole–dipole bonding, start to have a slightly higher boiling point than the straight chain 

methyl esters. This cannot be explained by our present knowledge. 

(e) The test is restricted to straight-chain compounds to try to keep other variables (like 

shape) constant. [Changing the shape of the compound greatly complicates the 

intermolecular forces between the molecules. Since the intermolecular forces depend on 

how close the molecules are to each other, the branches keep us from making accurate 

predictions.] 

(f) Since alcohols contain hydroxyl groups, which can form hydrogen bonds, the alcohols 

will have a higher boiling point, for a similar molar mass, than the alkanes and methyl 

esters. The alcohols will have a lower boiling point, for a similar molar mass, than the 

carboxylic acids because the extra carbonyl group on the acid will add more dipole– 

dipole forces and some additional locations for hydrogen bonding. 


(g) The prediction posed in 6(f) is verified as the boiling points of alcohols are between the 

carboxylic acids and the alkanes and methyl esters. 

7. Pro Perspectives 

Ecological: It is less wasteful to produce artificial flavours than to extract the flavour 

from natural sources and discard any unused parts. 

Esthetic: Artificial flavours have a more consistent flavour between batches, keeping 

products tasting the same for consumers over time. 

Con Perspectives 

Ecological: The production of artificial flavours uses up petrochemicals, which are a 

nonrenewable resource. 

Esthetic: Many consumers feel that artificial flavours do not taste as good as the flavours 

they are replacing. 

Investigation 10.3: Synthesis of an Ester 

(Pages 442, 463) 

Purpose 

The purpose of this investigation is to use the esterification generalization and diagnostic tests to 

synthesize and observe the properties of two esters. 

Problem 

What are some physical properties of ethyl ethanoate (ethyl acetate) and methyl salicylate? 

Evidence/Analysis 

Ester Solubility Odour 

ethyl ethanoate liquids mixed sweet, “gluey” smell 

methyl salicylate two layers formed wintergreen smell 

Investigation 10.4: Testing with Models 

(Pages 442, 464) 

[Prediction and Evaluation should not be required. The purpose should be to obtain a better 

understanding of a variety of organic reactions by building and observing molecular models. 

Orientation of molecules is important in many organic reactions, and the stereochemical 

formulas provide a method of recording this information.] 

Purpose 

The purpose of this investigation is to test stereochemical formula equations by using molecular 

models. 

Problem 

What are the stereochemical formula equations for the following reactions? 

(a) methane undergoes complete combustion 

(b) ethane is cracked into ethane 

(c) propane reacts with chlorine 

(d) but-2-ene reacts with water 

(e) ethanol eliminates water to produce ethane 

(f) 1-chloropropane undergoes an elimination reaction with hydroxide ions to produce propene, a 

chloride ion, and water 

(g) ethanol reacts with methanoic acid 


Prediction 

[This is not required.] 

Materials 

Molecular model kit, molecular model software program, or Internet virtual models. 

Evidence 

(a) 

(b) 

(c) 

(d) 

(e) 

(f) 

(g) 


Section 10.4 Questions 

[This is not required.] 

(Pages 443–444) 

1. 

Family General formula Naming system 

(a) Alcohols ROH [prefix]an-#-ol 

(b) Carboxylic acids RCOOH [prefix]anoic acid 

(c) Esters R 1 COOR 2 [prefix]yl [prefix]anoate 

2. An ester contains an —OR group in place of the —OH in the carboxylic acid. The OH group 

is responsible for the acidic properties of carboxylic acids, and also for hydrogen bonding; 

thus esters have lower melting and boiling points, are less soluble in water, and are less 

acidic. 

3. Procedure 

1. In a test tube, mix 5 mL of ethanol and acetic acid. 

2. In a fume hood, add 8–10 drops of concentrated sulfuric acid. 

3. Heat test tube and contents in a hot-water bath for 10–15 min, with a small beaker 

inverted over the test tube. 

4. Cool and observe contents. 

5. Dispose of the mixture into the sink with lots of cold water. 

CAUTION: Concentrated sulfuric acid is highly corrosive. Avoid contact with skin and 

clothing. Wear eye protection and a lab apron. Work under a fume hood and keep test tubes 

in a hot-water bath, away from people. Ethanol is flammable, so there should be no open 

flames in the vicinity. 

4. (a) HNO 3 + NaOH NaNO 3 + H 2 O 

nitric acid + sodium hydroxide sodium nitrate + water 

CH 3 COOH + CH 3 CH 2 CH 2 OH CH 3 COOCH 2 CH 2 CH 3 + H 2 O 

ethanoic acid + propan-1-ol propyl ethanoate + water 

Both inorganic salts and esters are formed by combining part of the reactant acid and the 

other “OH” reactant. Water is a product of both reactions. However, the inorganic salt is 

an ionic compound and the ester is a molecular compound. 

(b) The two unlabelled samples are observed or tested for state of matter, solubility in water, 

conductivity of solution, and flame test of the solution or pure sample. 

5. (a) (b) 


(c) 

6. (a) Neutralization 

(b) Esterification 

(c) Neutralization 

(d) Esterification 

7. 

8. (a) 

(b) 


(c) 

(d) 

(e) 

(f) 

(g) 

9. Purpose 

The purpose of this investigation is to test the esterification reaction generalization. 

Problem 

What is the product of the reaction between benzoic acid and ethanol? 

Prediction 

According to the esterification reaction generalization, 


Materials 

lab apron pure ethanol dropper bottle 

eye protection concentrated sulfuric acid 

two 25250 mm test tubes vial of benzoic acid 

250 mL beaker two 50 mL beakers 

laboratory scoop balance 

hot plate thermometer 

ring stand test tube clamp 

CAUTION: 

Concentrated sulfuric acid is dangerously corrosive. Protect your eyes and do not allow 

the acid to come in contact with skin, clothes, or paper. 

Ethanol is flammable. Keep ethanol away from open flame and from direct contact with 

the hot plate element. 

Excessive inhalation of the products may cause headaches or dizziness. Use your hand to 

waft the odour from the cooled test tube towards your nose. The laboratory area should 

be well ventilated. 

Analysis 

According to the evidence, the odour of cherries and the low solubility are both positive tests 

for the presence of ethyl benzoate ester. 

Evaluation 

On the basis of the limited evidence collected, it appears that the prediction is verified but the 

results are not very certain. Therefore, the esterification reaction generalization remains 

acceptable because no evidence was obtained to contradict it. The purpose was not really 

accomplished because the design was limited and only one reaction was investigated. 

Additional reactions with better tests need to be investigated. 

10. (a) C 25 H 51 COOH + C 32 H 63 OH C 25 H 51 COOC 32 H 63 + H 2 O 

(b) C 27 H 55 COOH + C 30 H 61 OH C 27 H 55 COOC 30 H 61 + H 2 O 

11. Pro Perspective 

Technological:Many carboxylic acids and esters are easier to produce artificially than to 

recover from natural products. 

Con Perspectives 

Mystical: Some people believe that natural sources of carboxylic acids like vitamin C are 

inherently better than manufactured sources because they are natural. 

Esthetic: Artificial flavours of synthetic esters are only approximate and are not as 

flavoursome as the natural product. 


Extension 

12. (a) 

(b) Animal hides decompose quickly unless they are cured to remove the water from the 

skin. The hide is first soaked in water to remove water-soluble substances, and hair is 

removed by soaking in a mixture of lime and water, followed by an enzyme mixture. The 

hair and any remaining tissue are removed by machine and the hide is washed and treated 

with tannic acid. The tannic acid displaces water from the spaces between the protein 

fibres of the hide, allowing the fibres to cement together to form a strong, water-resistant 

leather. 

13. (a) First molecule: one cis and two trans 

Second molecule: two cis and two trans 

(b) Transfats increase the level of low-density lipoprotein (LDL) or “bad” cholesterol in the 

bloodstream, which contributes to clogging of the arteries. As arteries clog, the risk of 

stroke and heart attack increases. 

10.5 POLYMERIZATION REACTIONS—MONOMERS AND POLYMERS 

Web Activity: Web Quest—Teflon: Healthy or Hazardous? 

(Page 448) 

[Students’ presentations may cover some of the following material.] 

Production of Teflon 

To produce polytetrafluoroethylene (PTFE or Teflon®), the manufacturer first needs a steady 

supply of tetrafluoroethylene (TFE). To produce the required TFE, three main ingredients, 

fluorspar, hydrofluoric acid, and chloroform are combined in a reaction chamber and heated to 

between 590 ˚C and 900 ˚C. The gas produced is cooled and then distilled to remove impurities. 

A possible sequence of reactions is: 

CaF 2 (s) + H 2 SO 4 (aq) CaSO 4 (s) + 2 HF(aq) 

CH 4 (g) + 3 Cl 2 (g) CHCl 3 (g) + 3 HCl(g) 

CHCl 3 (g) + 2 HF(g) CHClF 2 (g) + 2 HCl(g) 

2 CHClF 2 (g) CF 2 CF 2 (g) + 2 HCl(g)

10.4 CARBOXYLIC ACIDS ESTERS AND ESTERIFICATION REACTIONS

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