Eliminations from (E)-O-Arylbenzaldoximes Promoted by Tertiary Amines in Acetonitrile. Effects of Aryl Substituents, Base Strength, and Leaving Group upon the Nitrile-Forming Transition State

Article abstract of DOI:10.1021/ja00226a032

Elimination reactions of (E)-O-(2,4-dinitrophenyl)benzaldoximes (1) and (E)-O-picrylbenzaldoximes (2) with R3N in MeCN have been investigated.The reactions are quantitative, producing only benzonitriles and aryloxides.The observation of second-order kinetics, β = 0.43 - 0.81, and <β_1g> = 0.39 - 0.73 is consistent with an E2 mechanism.For reactions of 1 with R3N in MeCN, the β and ρ values increased significantly with electron-withdrawing aryl substituents and stronger bases respectively.The corresponding changes in the β and ρ values for 2 were in the same direction but much less.When the leaving group was changed from 2,4-dinitrophenoxide to picrate, however, β increased and ρ decreased.Changes in transition-state parameters with alteration in the reactant structure are interpreted as resulting from variation in a nitrile-forming transition state.