Acetylsalicylic Acid

Acetylsalicylic Acid

Experiment #8

Pg: 9-12

PURPOSE

The purpose of this experiment was to show that aspirin, otherwise known as acetylsalicylic acid, can be prepared by the reaction between salicylic acid and acetic anhydride. Through the process of crystallization, we should be able to extract acetylsalicylic acid.

REACTION EQUATION

C7H6O3 + C4H6O3  C9H8O4 + C2H4O2

Salicylic Acid + Acetic Anhydride  Acetylsalicylic Acid (Aspirin) + Acetic Acid

TABLE OF PHYSICAL CONSTANTS

Physical

Constant Molecular Weight Melting Point/ Boiling Point Density Hazards

Acetylsalicylic Acid 180.2 g/mol 135˚C / 140˚C 1.40 g/cm³

Acetic Anhydride 102.9 g/mol -73.1˚C / 140˚C 1.08 g/cm³

Salicylic Acid 138.1 g/mol 159˚C / 211˚C 1.44 g/cm³

Phosphoric Acid 98.00 g/mol 42.4˚C / 158˚C 1.88 g/cm³ Highly Corrosive

Water 18.01 g/mol 0.00˚C / 100˚C 1000 kg/m³

THEORETICAL YIELD

Acetic Anhydride (102.9 g/mol)

0.480 mL = .000480 L

.00480 L * 1.08 g/cm³ = .00518 mol

Salicylic Acid (138.1 g/mol)

0.210 g / 138.1 g/mol = .00152 mol

(Limiting Reagent)

.00152 mol * 1000 = 1.52 mmol

.210 g * 1000 = 210 mg

PROCEDURE

1. Set up 100 mL of water in a hot bath and set to 50˚C.

2. Weigh 0.210 g of salicylic acid and place in dry 5-mL conical vial.

3. Add 0.480 mL acetic anhydride followed by one drop of concentrated phosphoric acid.

4. Thoroughly mix solution using spin vane until salicylic acid dissolves.

5. Continue heating for 8-10 minutes after the solid completely dissolves.

6. Allow vial to cool to room temperate, during which the acetic acid begins crystallization.

7. After crystallization completes, add 3.0 mL water and stir thoroughly.

8. Vacuum filtrate using Hirsch funnel and 1 mL cold water to rinse product.

9. Continue

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