THE CONTRIBUTION OF QUANTUM-MECHANICAL TUNNELING TO THE 1,2-HYDROGEN REARRANGEMENT OF METHYLBROMOCARBENE

The rate constants for the 1,2-hydrogen rearrangement of methyl- and m ethyl-d(3)-bromocarbene have been determined as a function of temperat ure. The Arrhenius plots are curved, and the intermolecular isotope ef fect is small and may increase with increasing temperature. We believe that although the rearrangement proceeds classically at high temperat ures, as suggested by theory, quantum mechanical tunneling contributes significantly to the reaction at low temperatures. Alternative explan ations are presented and discussed.