REACTION OF (E)-O-ARYLBENZALDOXIMES WITH SODIUM METHOXIDE IN METHANOL - EFFECT OF LEAVING GROUP UPON NITRILE-FORMING TRANSITION-STATE

Reactions of (E)-O-arylbenzaldoximes 1-3 with MeONa-MeOH have been studied kinetically. The reactions proceed via competing E2 and S(N)Ar reactions, in which the first step is rate-determining. Although the reactions were strongly influenced by the electronic effect of the beta- and O-aryl substituents, they were insensitive to the steric effect of the O-aryl group, except that the S(N)Ar reaction was retarded by the CF3 group of 2. For eliminations from 1-3 promoted by MeONa-MeOH, the k(H)/k(D) value increased and the Hammett rho-value decreased with better leaving groups. From these results, the effect of leaving group variation upon the nitrile-forming transition state is assessed.