Abstract
Aryl esters of 4-hydroxybutyric acid, 5-hydroxyvaleric acid, 2-hydroxyphenylacetic acid, and 3-(2-hydroxyphenyl)propionic acid are lactonised in reactions whose rates are proportional to 10pH – pKW. The anchimeric assistance corresponds to rate enhancements of 103–106 over the rates of hydrolysis of analogous esters without the hydroxy-groups. The reaction of phenyl 4-hydroxybutyrate shows buffer catalysis, possibly general base catalysis, in acetate and phosphate buffers. The esters of 4-hydroxybutyric acid and 5-hydroxyvaleric acid also react with participation by the hydroxy-groups in the acid-catalysed hydrolysis but those of 2-hydroxyphenylacetic acid and 3-(2-hydroxyphenyl)propionic acid do not. The rate of hydrolysis of phenyl 4-hydroxybutyrate increases more rapidly with acid concentration than that of phenyl butyrate does. The ϕ values are 0·59 and 0·99 respectively. The hydrolyses of the lactones of 2-hydroxyphenylacetic acid and 3-(2-hydroxyphenyl)propionic acid were also studied.
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