LACK OF ENHANCed REACTIVITY OF α-NUCLEOPHILES In THE SN2 REACTIONS OF BENZYL BROMIDES AND SMALL α-EFFECT In THE MICHAEL ADDITION RECTION OF AMIDES TO P-TOLYL VINYL SULFONE

Abstract Both second-order rate constants of SN2 reactions on benzyl bromide and p-nitrobenzyl bromide with hydroxy nucleophiles and those of the Michael addition reactions of a few amines to p-tolyl vinyl sulfone have been determined. The values of kHOO-/kHO- for benzyl and p-nitrobenzyl bromide were very small, i.e., 1.3 and 1.2 respectively; in the SN 2 reaction on sp3carbon this may be due to the lack of tight σ-bond formation at the transition state. A very small positive deviation from the Bronsted plots was observed in the Michael addition of hydrazine and other amines to p-tolyl vinyl sulfone. This may be due to the small β-value associated with the reaction.