The reaction of trialkylamine with nitric acid in a mixture of acetic acid and acetic anhydride

Abstract

The nitric acid oxidation of trialkylamines has been studied in a mixture of acetic acid and acetic anhydride at 30–50°. The main product from triethylamine is N,N-diethylnitrosoamine and the minor ones are N,N-diethylacetamide and N,N-diethylformamide. On the other hand, the main product from tri-n-butylamine is N,N-di-n-butylformamide and the minor ones are N,N-di-n-butylnitrosoamine, N,N-di-n-butylacetamide and N,N-di-n-butylbutyramide. This reaction has a short induction period, which is minimized by introducing nitrous acid gas in the reaction mixture. The addition of hydrogen chloride and bromide or molecular bromide accelerates the reaction, giving N,N-dialkylnitrosoamine as a main product in either case. These facts suggest a mechanism involving a hydrogen atom abstraction with nitrogen dioxide followed by the formation of nitrite (II) and then imine (III) and the decomposition of II, III and/or enammonium ion (IV).