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