Kinetics and mechanism of the reaction between nitrous acid and hydroxylamine. Part III. The formation of hyponitrous acid

Abstract

The yield of a minor product of the reaction between nitrous acid and hydroxylamine, trans-hyponitrous acid, has been studied over a wide range of conditions. It has been shown that, for nitrosation of free hydroxylamine by four different neutral nitrosyl compounds, the yield varies with the nature of the reagent: ON·Br 27, ON·NCS 12, ON·NO₂ 6, and ON·Cl 15 %. For nitrosation of the hydroxylammonium ion by the nitrous-acidium ion the yield is 2·0 %. An isotopic study of the reaction shows that a symmetrical intermediate is involved in several cases, probably cis-hyponitrous acid. The results are interpreted as showing that the initial nitrosation is an electrophilic displacement of a proton rather than an addition reaction of the type thought to occur in diazotisation and deamination.