α-Deuterium kinetic isotope effects in reactions of methyllithium: is better aggregation the cause of lower reactivity?

Abstract

The values k H/ k D for α-deuterium kinetic isotope effects for the reaction of methyllithium and methylmagnesium iodide with a series of substrates are consistently ca. 10–15% higher for the lithium reagent than for the Grignard reagent. This may indicate a pre-equilibrium between an aggregate and a reactive monomer, with a better fit of the trideuterio monomer in the aggregate. An attempt has been made to compare the equilibrium constants for the aggregation of deuterio and protio methyllithium by studying the metal-halogen equilibrium between methyllithium and methyl iodide.