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

Abstract

In this paper, different hydrazines are synthesised by the indirect Raschig process. This consists of introducing a substituted chloramine (R 1 R 2 NCl) into liquid ammonia under pressure to obtain the corresponding hydrazine (R 1 R 2 NNH 2 ). 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 (NH 2 Cl) and the amine (R 1 R 2 NH) 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).

Ammonia–dimethylchloramine system: Kinetic approach in an aqueous medium and comparison with the mechanism involving liquid ammonia

“…The more concentrated the medium, the faster the rate of this reaction. These results explain also the reason why it is not possible to obtain UDMH in aqueous medium, even under extreme conditions and confirm the experimental results obtained by Yagil and Anbar 54. On the contrary, in liquid ammonia, under the most unfavorable conditions, a rate of UDMH equal to 8% is obtained 56.…”

“…These results obtained in our laboratory 56 are very interesting from a mechanistic point of view. However, they show that the mechanism involved in liquid ammonia under pressure, giving NH 2 Cl in the first step, is quite similar to the direct Raschig process with all its constraints.…”

Synthetic and biosynthetic routes to nitrogen–nitrogen bonds

“…13A). More recently, a modified Raschig process has been employed to synthesize substituted hydrazines 68 (Fig. 13A).…”