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Esters

Esters, R–CO–OR′, are the condensation derivatives of a carboxylic acid and an alcohol. They abound in nature (flavours, fats, waxes, membranes) and are key synthetic intermediates: they are hydrolysed, transesterified and reduced, and they form enolates.

Examples of ester names: methyl formate, isopropyl isobutyrate, ethyl cyclohexanecarboxylate, 2-benzyloxycarbonylbenzaldehyde, 2-benzylcarbonyloxybenzaldehyde and a δ-lactone (2-oxooxacyclohexane)

Nomenclature

 Molecular model of a lipid bilayer made of molecules with ester groups

Physical and Bond Properties

 Protonation of an acid derivative R–CO–L at the carbonyl oxygen and resonance forms of the cation, with the positive charge on the oxygen, the carbon and the L group

Acid-Base Properties

 Preparation of esters: Fischer esterification of 4-phenylbutanoic acid with excess ethanol, malonyl chloride with tert-butanol, phthalic anhydride with phenol, acetate with benzyl chloride and cyclohexanecarboxylic acid with diazomethane, with the resonance forms of diazomethane

Preparation

 Reactions of esters: acid hydrolysis of methyl benzoate with labelled water, saponification of (R)-2-butyl benzoate with retention of configuration (v = k[ester][HO⁻]) and transesterification with ethanol

Reactivity