Interaction between substituted chloramines and liquid ammonia using the indirect Raschig process

In this paper, different hydrazines are synthesised by the indirect Raschig process. This consists of introducing a substituted chloramine (R₁R₂NCl) into liquid ammonia under pressure to obtain the corresponding hydrazine (R₁R₂NNH₂). The experimental results, in disagreement with those reported in the literature, lead us to propose a new mechanistic scheme involving a chlorine transfer reaction. Thus, the formation of chloramine (NH₂Cl) and the amine (R₁R₂NH) occurs first. Chloramine reacts immediately with the substituted amine, in agreement with the direct Raschig process, to produce the hydrazine. Under these conditions, the nature of the hydrazine is kinetically controlled by the excess amine. It is then possible to synthesise different hydrazines from the same substituted chloramine. This mechanism is validated by the following syntheses: unsymmetric dimethylhydrazine (UDMH), N-aminopiperidine (NAPP) and N-amino 3-azabicyclo[3.3.0]octane (NAZA).