Nitration of Metyl Benzoate

Nitration of Methyl Benzoate

ABSTRACT

In the nitration of methyl benzoate experiment, methyl m-nitrobenzoate (C8H7NO4) will be synthesized from methyl benzoate (C8H802), nitric acid (HNO3) and sulfuric acid (H2SO4). Methyl m-nitrobenzoate (C8H7NO4) will be purified by crystallization with methanol using an electrophilic aromatic substitution reaction. Nitration is a general chemical process for the introduction of a nitro group into a chemical compound. The percent recovery of this reaction was 57.17% (table 6).

After crystallization, melting point indicated the product was methyl m-nitrobenzoate and that the reaction was successful, however the TLC plate failed to confirm this due to the solvent that was used was too polar causing the very polar isomers to stick to the TLC plate.

INTRODUCTION/PURPOSE

The purpose of this experiment was to synthesize methyl nitrobenzoate from methyl benzoate, concentrated nitric acid (HNO3), and concentrated sulfuric acid (H2SO4) using electrophilic aromatic substitution reaction. The product will then be isolated and crystallization with methanol and vacuum filtration for isolation. Following crystallization, melting point and TLC will be used to identify and characterize the product of the reaction. Electrophilic aromatic substitutions are reactions that when a hydrogen atom on an aromatic ring is replaced by and electropile.

EXPERIEMENTAL/PROCEDURES

Materials and Instruments

1. Iron ring and support bar

2. Clamp

3. Stir Plate

4. 250 mL beaker

5. 2 - Spotting pipets

6. TLC plate

7. 5 mL conical vial

8. Triangular spin vane

9. Crushed ice

10. Sulfuric acid (H2SO4)

11. Nitric Acid (HNO3)

12. Methyl benzoate

13. Methanol

14. Water

15. 5% acetic acid

16. UV light

Procedures and Observations

The procedures were followed from (Ref. 2).

1. Fill a 250 mL beaker with crushed ice. Set up stir plate.

2. Added 560 μL of methyl benzoate into a conical vial and placed into ice bath for 5 minutes.

* Observations: Clear liquid

3. Combined 240 μL of nitric acid and 240 μL of sulfuric acid in test tube and placed in ice bath.

4. Placed 3 mL deionized water into a test tube and placed in ice bath.

5. Removed conical vial containing sulfuric acid, clamped it above stir plate.

6. Added 200 μL methyl benzoate to conical vial, then added the test tube with 240 μL nitric acid and 240 μL sulfuric acid.

* Observations: The mixture turns from clear to brown with steam escaping

7. Allowed the solution to stir a room temperature for 15 minutes.

8. Stopped the reaction by adding 2 mL de-ionized ice water.

* Observations: Turned solution brown and white precipitate formed crystals

9. Placed the solution in ice bath for 10 minutes stirring with a glass rod several times.

* Observations: As the solution cooled, more white crystals formed

10. The precipitate was then collected using a Hirsch funnel using filter paper.

11. The solution that remained in the conical vial was then dissolved in approximately 1 mL dichloromethane for use in the TLC plate.

12. The crystals in the Hirsch funnel were rinsed with a mixture of cold methanol and water and allowed to vacuum for 5 minutes.

13. The crystals were then weighed.

14. Samples were then spotted on the TLC plate of 1) solution from conical vial 2) methyl p-nitrobenzoate 3) methyl m-nitrobenzoate and 4) methyl o-nitrobenzoate.

15. Use a developing chamber with 5% acetic acid; examine the TLC plate under a UV light.

16. The melting point was determined by using a melting point capillary

DATA/RESULTS

Mass of crystallized product: 0.165g

Theoretical yield: 0.2886g

Percent yield: 57.17%

Melting point crystallized product: 79 - 89oC

Literature Value: 78 - 80o C (Ref. 1)

Retention Factor Values

1. Methyl nitrobenzoate 2. Methyl p-nitrobenzoate 3. Methyl m-nitrobenzoate 4. Methyl o-nitrobenzoate

0.078 0.078 0.104 0.182

Table 1

Limiting Reagent

HNO3

0.24 mL HNO3 1.5027g HNO3 1 mol HNO3 1 mol methyl nitrobenzoate 181.3g methyl nitrobenzoate

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

Table 2

= 1.038g methyl