Esters (or alkyl alkanoates) are a class of organic compounds that typically have distinctive fruity aromas and flavors and are hence responsible for the odors/flavours of many fruits. The most common esters found in nature are fats and vegetable oils, which are esters of glycerol and fatty acids.

Esters are the functional group RCOOR and are produced when carboxylic acids are heated with alcohols in the presence of an acid catalyst (usually concentrated sulphuric acid). Fundamentally the hydrogen of the carboxylic acid (R-COOH) is replaced with the alkyl group (R) of the alcohol. This is known as esterification, a slow and reversible process. The diagram below is the general model of esterification:

The opposite reaction also occurs that synthesizes an ester into a carboxylic acid and an alcohol. The ester is hydrolyzed by the addition of water to produce acids and alcohols using acidic or basic...