An ester group is an important functional component in many chemical compounds such
as fatty acids and components of fragrances and flavors. Esters are widespread throughout
nature, but are also a vital use in industry. The synthesis of low molecular weight esters, by the
reaction of a carbonyl with an alcohol, is essential to the fragrance and flavoring industry. nButyl
acetate is a widely known ester used as a solvent in the production of lacquers, but more
commonly as a synthetic apple flavoring used in foods such as ice cream, candy, jams, and baked
goods.
n-Butyl acetate is synthesized by reacting acetic acid with n-butanol and ptoluenesulfonic
acid catalyst. This reaction is an example of a Fisher etherification or a
nucleophilic acyl substitution mechanism. The reaction precedes by protonating the carbonyl
oxygen of acetic acid with the catalyst p-toluenesulfonic acid. A resonance hybrid is formed
upon protonation and the resonance form that contains the electrophilic carbon is easily attacked
by the nucleophilic oxygen of the alcohol 1-butanol. The final product is formed by the removal
of a water molecule and subsequent deprotonation of the attached alcohol. The water is
physically removed as an azeotrope by distillation in a modified Dean-Stark apparatus. It is
important to remove the water so the reaction mixture will not reach equilibrium. By Le
Chatelier’s principle, if the water is continuously removed the reaction must continue to drive
forward producing pure n-butyl acetate.