Kinetics and mechanisms of oxidations with nitrous acid. Part 1. Substituted benzyl alcohols and benzyl methyl ether in aqueous sulphuric acid

Abstract

The kinetics and products of oxidation of several substituted benzyl alcohols and of benzyl methyl ether, by nitrous acid in aqueous sulphuric acid (30–50%) at 25 °C, have been investigated. Conversion into substituted benzaldehyde, when nitrous acid is taken in excess, is quantitative. Stoicheiometry, kinetic form, kinetic and product hydrogen isotope effects, and the dependence of rate coefficients on acidity, support a mechanism in which there is rate-determining abstraction by the nitrosonium ion of a hydride ion, either in one step or by electron transfer followed by hydrogen-atom abstraction, from the α-carbon atom of the alcohol or ether. The fate of the HNO so formed depends upon the presence or absence of oxygen.