A primary kinetic isotope effect could most likely be observed in which of the following mechanisms? A)S_N1 and S_N2 B)S_N2 C)E1 and S_N1 D)E2 E)E1

Question

Quizplus · Accepted Answer

The primary kinetic isotope effect occurs when the rate-determining step involves the breaking of a covalent bond that is vibrationally sensitive to the mass of the isotopic substitution. In the E2 mechanism, the rate-determining step involves the simultaneous formation of the carbon-carbon double bond and cleavage of the leaving group, which is a bond-breaking process. Therefore, a primary kinetic isotope effect would most likely be observed in the E2 mechanism.

A Primary Kinetic Isotope Effect Could Most Likely Be Observed