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

After an exhaustive study of the system ammonia-dimethylchloramine in liquid ammonia, it was interesting to compare the reactivity of this system in liquid ammonia with the same systeme in an aqueous medium. Dimethylchloramine prepared in a pure state, undergoes dehydrohalogenation in an alkaline medium: the principal products formed are Nmethylmethanimine, 1,3,5-trimethylhexahydrotriazine, formaldehyde and methylamine. The kinetics of this reaction was studied by UV, GC and HPLC as a function of temperature, initial concentrations of sodium hydroxide and chlorinated derivative. The reaction is of the second order and obeys an E2 mechanism (k1 = 4.2 × 10 -5 M-1 s-1, ∆H° # = 82 kJ mol-1, ∆S° # = 59 J mol-1 K-1). The oxidation of unsymmetrical dimethylhydrazine by dimethylchloramine involves two consecutive processes. The first step follows a first-order law with respect to the haloamine and the hydrazine, leading to the formation of an aminonitrene intermediate (k2 = 150 x 10 -5 M -1 s -1 ). The second step corresponds to the conversion of aminonitrene into formaldehyde dimethylhydrazone at pH=13). This reaction follows a first-order law (k3 = 23.5 x 10 -5 s -1 ). ha l-0 03 97 54 3, v er si on 1 23 J un 2 00 9 Author manuscript, published in "International Journal of Chemical Kinetics 40, 6 (2008) 340-351"