Mechanistic Significances of the Reactivity-Selectivity Principle

摘要

The relationship between the signs of ヱi(0), ヱ j(0) and ヱij and validity of the reactivity-selectivity principle (RSP) has been derived: RSP is valid when W = ヱi(0)·ヱj(0)/ヱij is negative. The analysis of 100 reaction series indicated that for normal SN2 reactions involving variations of substituents in the nucleophile (X) and in the substrate (Y) RSP is valid only for a dissociative type for which ヱY(0) is negative, whereas for the acyl transfer reactions with rate-limiting breakdown of the tetrahedral intermediate RSP is valid in general for all substituent changes, X, Y and/or Z (substituent on the leaving group). The trends in the validity of RSP for certain types of reaction can be useful in supplementing the mechanistic criteria based on the signs of ヱi(0), ヱj(0) and ヱij.