An unusual case of carbonnitrogen bond formation. Reactivity of a C-nitroso group toward acyl chlorides

Acyl chlorides react with nitrosobenzene in 99.9% acetonitrile and in the presence of catalytic amounts of HCl giving the corresponding N-p-chlorophenylhydroxamic acids. The spectroscopic and kinetic evidence obtained indicates that the reaction is initiated by the formation of an N-chlorohydroxylamine intermediate from nitrosobenzene and hydrochloride in the first, slow step of the process. The nucleophilic N-chlorohydroxylamine intermediate reacts with acyl chloride (or possibly an acyl cation–chloride ion pair) to give the addition acylnitroso intermediate which undergoes to nucleophilic attack by chloride ion at the para position of the phenyl moiety and, after proton transfer from carbon, the corresponding N-p-chlorophenylhydroxamic acid is formed.