ABSTRACT The activation parameters for transesterification of 4-nitrophenyl benzoates with thiophenol in the presence of K2CO3 in DMF were compared with the ones for the same reaction with 4-chlorophenol. The increase of the activation parameters occurs for the reactions with S-nucleophile relative to that with O-nucleophile. This is probably caused by the structure variation of the transition states. It was found that positive values of activation entropy were observed for transesterification of 4-nitrophenyl 4’-R-substituted benzoates (R = H, Me, OMe) with S-nucleophile. It may result from the differences in solvation of initial reagents and transition state (TSS) in the reaction rate - limiting step. The results obtained show that the influence of the substituent and nucleophile nature on the activation parameters in the transesterification is governed by the solvation contribution.
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