Reinterpretation of the kinetic data and the non-steady state hypothesis (two-step mechanism) for the SN2 reaction between p-nitrophenoxide and methyl iodide in aprotic solvents containing water

Abstract

Kinetic data obtained by conventional spectrophotometry for reaction of sodium p-nitrophenoxide with methyl iodide in degassed acetone are reported. The rate constants obtained from the first 10% of reaction do not differ significantly from those obtained over longer reaction times (e.g. 50% reaction)—the main criteria of Parker et al. (Org. Biomol. Chem., 2003, 1, 36–38) for a non-steady state two-step mechanism. Reactions are accelerated by crown ether, suggesting a mechanism via a free ion pair. Product studies by high performance liquid chromatography of reactions in aqueous acetonitrile (used by Parker et al.) show that the yield of methylated product is strongly affected by at least two base-neutralising side reactions.