Nitrating Methyl Benzoate: Electrophilic Aromatic ... - Franklin College

Nitrating Methyl Benzoate: Electrophilic Aromatic Substitution 


Leah Monroe 

March 25, 2003 

Organic Chemistry Lab II 

Experiment performed on March 13 and 18, 2003 

Abstract: The purpose of this experiment was to synthesize methyl nitrobenzoate from methyl benzoate, 

concentrated HNO3, and concentrated H2SO4 via an electrophilic aromatic substitution reaction. The 

HNO3 and H2SO4 were combined to form a nitrating solution, which was mixed with a mixture of 

methyl benzoate and H2SO4. The resulting mixture sat in an ice-water bath for 40 minutes, then had 

10 mL chilled water added to it. The solution was then allowed to sit for an additional 10 minutes to 

complete crystal formation. The crystals were then collected using vacuum filtration. The product was 

isolated and recrystallized using 95% ethanol. Following recrystallization, melting point and infrared 

spectrum were used to identify and characterize the product of the reaction. The percent recovery of 

this reaction for the recrystallized product was 56.42%. Percent yield for the crude product and 

percent recovery following recrystallization were not calculated because the written procedure from 

the reference did not require it. Melting point and infrared spectroscopy analyses indicated the 

product was indeed methyl m-nitrobenzoate and that the reaction was successful.


Introduction: The purpose of this experiment is to synthesize methyl nitrobenzoate from methyl benzoate, 

concentrated HNO3, and concentrated H2SO4 via an electrophilic aromatic substitution reaction. 

The product will then be isolated and recrystallized using 95% ethanol. Following 

recrystallization, melting point and infrared spectrum will be used to identify and characterize the 

product of the reaction. Regiochemistry of the product will also be determined. 

Materials Used: 

50-mL beaker 50-mL graduated cylinder 

400-mL beaker marking pen 

Hirsch funnel with tubing microspatula 

25-mL Erlenmeyer flask 3 Pasteur pipets, with latex bulb 

125-mL Erlenmeyer flask 3 pipets, 1-mL, with rubber bulb 

glass stirring rod sand bath 

10-mL graduated cylinder support stand 

utility clamp 2 test tubes, 15 x 125-mm 

Reagents and Properties: 

Substances Formula Weight Quantity 

g/mol 

Moles Used Mole Ratio Melting Point 

°C 

Boiling Point Density 

°C 

Methyl benzoate 136.15 0.55 g 4.039 x 10 -3 1 to 1 113 – 115 N/A N/A 

Methyl nitrobenzoate 181.13 product N/A 1 to 1 78 – 80 N/A N/A 

Conc. Nitric acid 63.01 0.5 mL 1.192 x 10 -2 N/A N/A 121 1.5027 g/mL 

Conc. sulfuric acid 98.08 1.6 mL 3.0 x 10 -2 N/A N/A N/A 1.841 g/mL 

Ethanol, 95% 46.07 2-3 mL N/A N/A N/A N/A N/A 

Reaction and its Mechanism: 

Overall Reaction: 

O 

C 

Methyl benzoate 

OCH3 

HNO3 

H2SO4 

NO2 

O 

C 

Methyl m-nitrobenzoate 

OCH3 

+ H2O + H2SO4

Mechanism: 

Procedure: 

.. 

O 

N 

.. H 

O 

Nitric Acid 

O 

C 

O - 

.. 

.. 

O N O 

+ 


OCH3 

+ H O SO3H 

Sulfuric Acid 

NO2 

H 

+ 

- O 

O 

C 

H 

OCH3 

SO3H 

+ 

H 

O 

N 

O 

O - 

.. 

.. 

- O 

N 

+ 

+ SO3H O O 

NO2 

O 

C 


OCH3 

+ 

H2SO4 

+ H2O 

Part 1 – Preparing the Ice-Water Bath and Chilled Water 

Place equal volumes of ice and tap water into a 400-mL beaker so that the beaker is approximately 75% full. Then, 

prepare chilled water for parts three and four of this experiment by pouring approximately 30 mL distilled or 

deionized water into a 125-mL Erlenmeyer flask. Place the flask into the ice-water bath. 

Part 2 – Preparing the Nitrating Solution 

Label two 15 x 125-mm test tubes “nitric acid” and “sulfuric acid”, respectively. Transfer 0.5 mL concentrated nitric 

acid into the tube labeled “nitric acid.” Then, transfer 0.6 mL concentrated sulfuric acid into the tube labeled “sulfuric 

acid”. Chill both the test tubes with the acids in them in the ice-water bath for 15 minutes. Then, use a Pasteur pipet 

to very slowly add the cold sulfuric acid drop by drop into the cold nitric acid. Swirl the reaction mixture after every 

three drops are added. After adding all the sulfuric acid to the nitric acid, allow the nitrating solution to stand in the 

ice-water bath for 10 minutes. 

Part 3 – Nitrating Methyl Benzoate 

Place approximately 0.55 g methyl benzoate into a 25-mL Erlenmeyer flask and add 1.0 mL concentrated sulfuric 

acid. Clamp the flask containing the mixture to a support stand. Lower the flask into the ice-water bath for 5 minutes, 

being sure to prevent the bath water from entering the reaction flask. After the 5 minutes are up, use a Pasteur pipet to 

slowly add the nitrating solution in the test tube to the Erlenmeyer flask containing the methyl benzoate and sulfuric 

acid. After all the nitrating solution has been added, allow the mixture to stand in the ice-water bath for 30-45 

minutes. Make sure you swirl the flask every 5 minutes. After the 30-45 minutes are up, add 10 mL chilled water to a 

50-mL beaker. Slowly and carefully add the cold reaction mixture, with stirring, to the chilled water. Then, allow the 

chilled solution to stand 5-10 minutes to complete crystal formation. 

Part 4 – Isolating, Purifying, and Characterizing the Product 

Filter the reaction mixture via vacuum filtration. Wash the crystals with approximately 10 m L of chilled water in 

order to remove any residual acid. Then, allow your product to air dry in the filter tunnel for 10 minutes. Then, put 

your product crystals into a 10-mL Erlenmeyer flask and add 1 mL of 95% ethanol. Swirl the flask to mix. Heat the 

flask in a sand bath until the crystals are in solution and the solution boils. Boil the solution for a couple minutes, then 

remove the flask from the sand bath and allow it to cool to room temperature. Add approximately 0.5 mL ice-cold 

ethanol to the flask and swirl to loosen the crystals. Then filter the crystals using vacuum filtration. Allow the product 

to dry in the filter funnel for a couple days. Then, weigh your product and record its mass.


Part 5 – Melting Points and Infrared Spectrum 

Prepare a melting point capillary of the recrystallized product and take its melting point. Also, perform an infrared 

spectrum on the recrystallized product. Do this by adding 100 mg KBR to approximately 1mg of the recrystallized 

product. Mix the two using a mortar and pestle, being sure to grind the two compounds into a fine powder. Place some 

of this mixture in a microcup, making sure the surface is smooth. Then place the pellet in the infrared spectrometer 

and obtain an infrared spectrum of the product. 

Part 5 – Clean Up 

Place all waste materials in their appropriate waste containers. 

Data and Calculations: 

Mass methyl benzoate used: 0.554 g 

Mass recrystallized crystals: 0.413 g 

Percent Yield: 56.42% 

Melting Point recrystallized product: 77.5 - 80°C 

Literature Value: 78 - 80°C 

Finding Limiting Reagent 

HNO3 (0.5 mL HNO3) (1.5027 g HNO3) (1 mol HNO3) (1 mol methyl nitrobenzoate) (181.3 g methyl nitrobenzoate) 

(1 mL HNO3) (63.01 g HNO3) (1 mol HNO3) (1 mol methyl nitrobenzoate) 

= 2.159 g methyl nitrobenzoate 

H2SO4 (0.6 mL H2SO4) (1.841 g H2SO4) (1 mol H2SO4) (1 mol methyl nitrobenzoate) (181.3 g methyl nitrobenzoate) 

(1 mL H2SO4) (98.08 g H2SO4) (1 mol H2SO4) (1 mol methyl nitrobenzoate) 


Methyl Benzoate (0.554 g methyl benzoate) (1 mol methyl benzoate) (1 mol methyl nitrobenzoate) (181.13 g methyl nitrobenzoate) 

(136.15 g methyl benzoate) (1 mol methyl benzoate) (1 mol methyl nitrobenzoate) 


The limiting reagent for this electrophilic aromatic substitution reaction is methyl benzoate. It yields the least amount of 

methyl nitrobenzoate in this reaction, and therefore is the limiting reagent. 

Theoretical Yield 

(0.554 g methyl benzoate) (1 mol methyl benzoate) (1 mol methyl nitrobenzoate) (181.13 g methyl nitrobenzoate) 

(136.15 g methyl benzoate) (1 mol methyl benzoate) (1 mol methyl nitrobenzoate) 


Percent Yield 

For recrystallized product (mass of recrystallized methyl nitrobenzoate) (0.413 g methyl nitrobenzoate) x (100) = 

(theoretical yield) (0.732 g methyl nitrobenzoate) 

=56.42% yield


Observed Properties and IR Data and Interpretation: 

An infrared spectrum of the recrystallized product revealed that it was methyl m-nitrobenzoate. The peak located at 

1534.48 cm -1 indicates the presence of an –NO2 group. The peak located at 1734.33 cm -1 is the result of a carbonyl 

group and the peak at 1584.9 cm -1 indicates the presence of a benzene ring. Also, the peak at 1076.30 cm -1 indicates a 

C—O bond, which is present in methyl m-nitrobenzoate. Regarding the regiochemistry of the obtained product, the 

peak at 823.14 cm -1 indicated that the product was a meta-substituted benzene, as was predicted. All these peaks 

together indicate that the product was methyl m-nitrobenzoate. 

Results and Conclusions: 

The electrophilic aromatic substitution reaction between methyl benzoate and a nitrating solution of sulfuric and nitric 

acids was successful and yielded methyl m-nitrobenzoate. The percent yield of the recrystallized product was 56.42%. 

Percent yield of the crude product was not calculated because the experiment did not include this step and consequently, 

percent recovery for the recrystallized product cannot be calculated either. 

The melting point of the recrystallized product was 77.5 - 80°C. This was then compared with a data table given in the 

experiment in order to determine the regiochemistry of the obtained product. The observed melting point was extremely 

close to the literature value of 78 - 80°C for the meta-substituted product. Therefore, analysis of the melting point 

determined that the product was methyl meta-nitrobenzoate, as could be predicted. Since –CO2H3 is a strongly 

deactivating group, it is meta-directing. Thus, we expected the –NO2 group to be added to the methyl benzoate at the 

meta position. The melting point analysis proved that this is what happened and the product obtained was methyl mnitrobenzoate. 

An infrared spectrum of the product also confirmed its identity as methyl m-nitrobenzoate. A peak located at 1534.48 

cm -1 indicated the presence of an –NO2 group. The peak located at 1734.33 cm -1 was the result of a carbonyl group and 

the peak at 1584.9 cm -1 indicated the presence of a benzene ring. Another peak at 1076.30 cm -1 indicated a C—O bond, 

which is present in methyl m-nitrobenzoate. Regarding the regiochemistry of the obtained product, the peak at 823.14 

cm -1 indicated that the product was a meta-substituted benzene, as was predicted. All these peaks together indicated that 

the product was methyl m-nitrobenzoate. 

Reference: 

Chemistry Lab Experiments CHEM 224 REAC 716 pgs. 61 – 71 

By Wigal/Manion/LeFevre/Wade, Jr./Rapp/Lee/Wikholm 

Weast, Robert C., ed. CRC Handbook of Chemistry and Physics. 70 th ed. Boca Raton, FL: CRC Press, Inc., 1990. 

Post-Lab Questions: 

1. (a) The percent yield of my product was 56.42%. See Data section for calculation. 

(b) The melting point of my product was 77.5 - 80°C. 

(c) The observed melting point of 77.5 - 80°C was most closely related to the literature melting point of 78 – 

80°C for a meta substitututed product. Therefore, my product has a meta- regiochemistry. The meta- 

product forms because the ortho- and para- products both have very unstable resonance forms with 2 

positive charges next to each other. The two positive charges right next to one another cause the 

resonance forms to be unstable, so ortho- and para- substituted products do not form in this reaction. The 

meta- position is electron-rich, and thus reacts best with the –NO2 group to form methyl m-nitrobenzoate. 

Also, we knew the meta- product was going to form because –CO2H3 is a strongly deactivating group and 

is meta-directing. Thus, we expected the –NO2 group to be added to the methyl benzoate at the meta 

position. This was confirmed by analyzing the melting point.


(d) The structure of my product is: 

O 

NO2 

C 


OCH3 

2. The resonance forms for the arenium ion formed during this reaction are as follows: 

O 

C 

+ 

OCH3 

NO2 

+ 

O 

C 

OCH3 

NO2 


OCH3 

3. The first nitration proceeds much faster than the second two because the first –NO2 group to be added is 

added to the isolated toluene. The methyl group on the benzene ring is an activating group. It causes the 

benzene ring to be more electron rich and thus, have a high reactivity. –CH3 is an ortho-para activator. So, 

the first –NO2 group adds to the toluene in the para-position in order to avoid steric crowding from the 

methyl group. The toluene has now been converted to para- nitrotoluene. The –NO2 group that is now on 

the benzene ring is a deactivating group, and causes the benzene ring to be not nearly as reactive as it was 

before the first –NO2 group was added. Thus, the second and third nitrations occur much more slowly 

than does the first one. 

O 

C 

+ 

NO2

Nitrating Methyl Benzoate: Electrophilic Aromatic ... - Franklin College

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