ELIMINATION-REACTIONS OF (E)-O-PIVALOYLBENZALDOXIMES

Elimination reactions of (E)-O-pivaloylbenzaldoximes promoted by Et3N-MeCN, t-BuOK-t-BuOH, and t-BuOK-DMSO have been studied kinetically. The reactions produce benzonitrile quantitatively. The reactions are second-order and exhibit substantial values of rho,beta, and k(H)/k(D) and an E2 mechanism is evident. The rate of elimination from (E)-O-pivaloylbenzaldoxime increased with base-solvent system variation and gave relative rates of 1, 14.8, and 4.31 X 10(4) for Et3N-MeCN, t-BuOK-t-BuOH, t-BuOK-DMSO, respectively. The k(H)/k(D) value increased, but the Hammett rho value increased and then decreased, with this change in the base-solvent system. These results are compared with the predictions of the More O'Ferrall-Jencks reaction coordinate diagram to assess its scope and limitations in the interpretation of the elimination reactions.