arylaesterit

Arylaesterit, or aryl esters, are esters in which the alkoxy fragment is an aryl group. In the common form R-CO-O-Ar, the acyl part derives from a carboxylic acid (R-COOH) and the alcohol part from a phenol or substituted phenol (Ar-OH). The physical properties and reactivity of aryl esters depend on the aryl substituents.

Preparation methods include studying several routes: reaction of carboxylic acids with phenols under activating conditions (for example, using coupling reagents or acidic catalysis), reaction of acyl chlorides with phenols, or transesterification of existing esters with phenols to swap the aryl group. Activated aryl esters such as p-nitrophenyl esters are especially useful because the corresponding phenoxide is a good leaving group, facilitating acyl transfer.

Reactivity and behavior vary with the aryl moiety. Electron-withdrawing substituents on the aryl ring tend to increase the rate of hydrolysis and transesterification, while electron-donating groups can slow them. Compared with many alkyl esters, aryl esters can be more or less reactive depending on the activation and substitution pattern; highly activated aryl esters are commonly used as leaving groups in chemical and biochemical applications.

Applications of aryl esters are broad. They appear in fragrances and flavors, as intermediates in pharmaceutical and polymer synthesis, and as activated esters for enzyme assays, bioconjugation, and peptide chemistry. They also serve as protecting groups in multi-step syntheses, where selective deprotection reveals a carboxyl functionality.

See also: esters, phenyl esters, activated esters.