Experiment 82

Objective

To synthesize aspirin (acetylsalicylic acid) from salicylic acid by reacting it with acetic anhydride in the presence of sulfuric acid as a catalyst.

Introduction

Aspirin is synthesized by heating salicylic acid with acetic anhydride in the presence of sulfuric acid. The acetylation of salicylic acid produces aspirin and acetic acid as byproducts.

Reaction Overview

C7H6​O3​ + (CH3​CO)2​O → C9​H8​O4 + CH3​COOH

(Salicylic Acid + Acetic Anhydride → Aspirin + Acetic Acid)

Materials

Chemicals

·       Salicylic acid (3.659 g)

·       Acetic anhydride (9-10 mL)

·       Sulfuric acid (H₂SO₄)

·       Ethanol (for dilution)

Apparatus

·       Beaker

·       Glass rod

·       Electric heater

·       Pipette

Reagents

·       3.659 g of salicylic acid and 9-10 mL of acetic anhydride, with 1-2 drops of sulfuric acid as a catalyst.

Procedure

1.    Preparation of Reaction Mixture

o   Place salicylic acid and acetic anhydride in a beaker.

o   Add 1-2 drops of sulfuric acid to catalyze the reaction.

2.    Heating

o   Heat the mixture to 60°C on an electric heater, ensuring the temperature remains constant.

3.    Stirring

o   Stir the mixture using a glass rod for 5-10 minutes to complete the reaction.

4.    Crystallization

o   Allow the mixture to cool, then dilute it with ethanol and place it in a cooler environment to facilitate crystal formation.

5.    Isolation of Aspirin

o   Filter the mixture to collect aspirin crystals.

Observation

Aspirin crystallizes as a solid with a mild, sweet odor, indicating successful synthesis.

Questions

1.    What is aspirin?

2.    How is aspirin synthesized from salicylic acid?

3.    How is aspirin separated from the reaction mixture?

4.    What are the uses of aspirin?