Esters are obtained by the dehydration of an alcohol and an acid. This dehydration takes place under milder conditions than dehydration of two alcohol molecules to form an ether, and thus occurs preferentially. Ester formation, or esterification, is catalysed by acid and requires only mild heating:




Esterification formally resembles the process of acid-base neutralization in the way that an alcohol formally resembles a base, but the resemblance is only superficial. An ester is a covalently bonded, nonionizing organic molecule, not an ionized salt. Esterification is a particularly good example of a reaction that does not go to completion. Equilibrium is reached while appreciable quantities of both reactants and products remain. For this reason, esterification and the reverse process, hydrolysis, were among the earliest reactions whose kinetics were studied. We have seen the results of some of these studies in Chapter 15.

Right (From top): "Roadsign" for an ester, Benzyl acetate (jasmine), Ethyl benzoate (berry).