Reactions at high pressure. Part 5. The effect of pressure on some primary kinetic isotope effects

Abstract

Primary kinetic isotope effects for the reactions; diphenyldiazomethane–benzoic [²H]acid and [²H]leuco-Crystal Violet–chloranil have been determined at pressures up to 2 kbar. The former shows k_H/k_D <5, almost invariant with pressure while for the latter, believed to possess a significant tunnelling contribution, k_H/k_D falls from 11.5 to 7.5 at 2 kbar. It is suggested that increased solvation of the proton under pressure diminishes the extent of tunnelling.