Reactivity–selectivity relationships. Part 6. Application of the reactivity–selectivity principle to solvolytic reactions. Possible evidence for ion pair intermediates in SN2 solvolyses

Abstract

The reactivity–selectivity principle has been applied to the study of the solvolytic behaviour of octyl, 1-methylheptyl, and benzyl derivatives toward the competing nucleophiles, ethanol and water. Low selectivity values, k_E/k_W, are observed for these substrates. The results are interpreted as possible evidence for ion pair intermediates in S_N2 solvolyses. The effect of changes in substrate, solvent polarity, leaving group, and temperature are consistent with this interpretation. In the presence of a strong nucleophile, such as azide ion, a traditional S_N2 pathway is indicated.