SolutionsPreparation
1. Fischer esterification
Acetic acid and ethanol in a 1:1 ratio with H2SO4 give only 67 % ethyl acetate. Suggest two ways to increase the yield.
- Use an excess of one of the reagents, usually the alcohol.
- Remove the water as it forms (azeotropic distillation or a drying agent).
The reaction is an equilibrium; by Le Châtelier's principle, both measures shift it towards the ester.
2. Choose the method
How would you prepare: a) tert-butyl acetate; b) methyl cyclohexanecarboxylate, on a small scale and under mild conditions?
- From acetyl chloride (or acetic anhydride) and tert-butanol in the presence of a base: Fischer esterification works badly with tertiary alcohols, which dehydrate in acid.
- With diazomethane in ether on cyclohexanecarboxylic acid (with care), or from the carboxylate and methyl iodide.