The reactivity of dinitrogen trioxide and of nitrosyl thiocyanate

The reactions of dinitrogen trioxide as an electrophilic nitrosating agent with the azide ion and with m-chlorophenylhydrazine occur at rates close to the encounter limit. From the temperature variation of features in the kinetics of the reaction with azide ion it is calculated that ΔH for the formation of N2O3(aq) from 2HNO2(aq) is close to zero. Arguments are advanced to suggest that nitrosyl thiocyanate reacts with the azide ion and not with hydrazoic acid.