KINETICS AND MECHANISM OF AMINOLYSIS OF PHENYL ACETATES AND PHENYL TRIMETHYLACETATES IN DIMETHYL-SULFOXIDE

Kinetic studies have been carried out on the reactions of phenyl aceta tes and phenyl trimethylacetates in dimethyl sulfoxide. The rate ratio s between the two acyl compounds, and the positive sign and large magn itude of the cross-interaction constants, rho(xz,) between substituent s X in the nucleophile and Z in the leaving group are considered to fa vour the rate-limiting expulsion of aryl oxide from the tetrahedral in termediate T-+/-. The aprotic solvent used makes the proposed mechanis m with a cyclic transition state more attractive especially in view of the greater charge dispersion and assistance to leaving group departu re provided in such a structure.