Kinetic Isotope Effects in the Reduction of Methyl Iodide

a-Deuterium kinetic isotope effects (KIE's) have been determined for the reaction of methyl iodide with a series of reducing agents. Reagents which transfer hydride ion in an SN2 reaction show small inverse or small normal KIE's. Reagents which transfer an electron to methyl iodide to produce methyl radical show large normal KIE's up to 20 % per a-D.

Large KIE's were found for the reaction of methyl iodide with sodium, for Pd-catalyzed reaction of methyl iodide with hydrogen, for ET at a platinum cathode, for ET from benzophenone ketyl or from sodium naphthalenide, for iron catalyzed ET from a Grignard reagent to methyl iodide, and for reduction of methyl iodide with tributyltin hydride or with gaseous hydrogen iodide.

Very small KIE's were found for electron transfer to methyl iodide from magnesium in ether or from sodium in ammonia. The reason may be that these reactions are transport or diffusion controlled.