The Preparation of Aspirin The purpose of this experiment is to synthesize aspirin (acetyl salicylic acid) from salicylic acid and acetic anhydride. CO2H OH salicylic acid 2g 0. 014 mole O O O CH3 H2SO4 ethyl acetate CO2H O O acetyl salicylic acid acetic acid CH3 O + H3C + H3C OH acetic anhydride 5 mL 0. 05 mole The limiting reagent is salicylic acid. The theoretical yield of acetyl salicylic acid is 2. 52 g. Physical Data:* mp MW salicylic acid 157-9? 138 acetyl salicylic acid 135-6?
180 acetic anhydride — 102 acetic acid — 60 sulfuric acid — 98 ethyl acetate — 88 *Data from the CRC, 70th ed. bp — — 138? 117-8? — 77? density — — 1. 08 1. 049 1. 84 0. 90 solubility al, eth, ace al, eth, chl — — — — hazards toxic irritant corrosive, lachrymator corrosive corrosive flammable Calculations: 2 g salicylic acid (1 mole/138 g) = 0. 014 moles 5 mL acetic anhydride (1. 08 g/mL) = 5. 4 g then, 5. 4 g (1 mole/102 g) = 0. 05 moles thus salicylic acid is present in the lesser molar amount and is the limiting reagent therefore the theoretical yield of acetyl salicylic acid is 0.
014 moles, or 0. 014 moles (180 g/mole) = 2. 52 g Procedure From: Experiments for Organic Chemistry, Chem 3341, Spring 2000, pp. 20-25 1) Mix salicylic acid and acetic anhydride in a 125 mL Erlenmeyer flask, add 5 drops H2SO4. 2) Heat on steam bath for 10 min, then cool. 3) Add 50 mL water and cool on ice. 4) Collect product by vacuum filtration. 5) Air dry the crude product crystals and determine a crude yield. 6) Purify as in the flow chart below. on the next page. SIGNATURE DATE John Doe 2/29/00.