Diazene formation from hydrazines

Acyclic ADC compounds, which are more correctly named as derivatives of diazene, are generally prepared from hydrazine derivatives. For example, diethyl azodicarboxylate (Chemical Abstracts name diethyl diazene-1,2-dicarboxylate)5 is prepared from hydrazine by treatment with ethyl chloro-formate followed by oxidation with chlorine in benzene-water.6 Other oxidants which have been used include JV-bromosuccinimide,7 nitric acid,8 inorganic nitrates,9 potassium dichromate,10 silver carbonate on celite,11 and phenyl iodosotrifluoroacetate.12 The hydrazine derivative may also be... 

The major product formed from brisk protolysis, occurring with the evolution of nitrogen, is hydrazine in 80-90% yield, which among other products arises from disproportionation of diazene 2 N2H2 - N2H4 + N2 (6, 8). Moreover, ammonia and hydrazoic acid are formed, with additional formation of hydrogen in a strong alkaline milieu. The formation of the latter is characteristic of base-catalyzed dissociation of diazene (8) ... 

The recently confirmed inhibition of cytochrome P-450 by Isoniazid and hydralazine does not result from heme alkylation but rather from the formation of a transient complex with an absorption maximum at 449 nm.41-44 xjjg complex and its inhibitory effect are dissipated by ferrl-cyanide. The Inhibition by isoniazid thus resembles that mediated by 1,1-disubstituted hydrazines, which also form reversible cytochrome P-450 complexes absorbing at 449 nm. 5 studies with metalloporphyrins indicate that 1,1-dialkyIhydrazines are oxidized to amlnonitrenes that coordinate to the iron atom. The coordination of diazene metabolites with the heme of cytochrome P-450 also yields complexes with an absorbance maximum at 446 nm. ... 

The bond dissociation energies Do(HNNH-H) = 183 4.6 [14] and 184 kJ/mol [12] were derived from the ionization potential of N2H3. A well-agreeing value of Do(HNNH-H) = 182 kJ/ mol was obtained by a MP2 calculation [2]. A mean N-H bond dissociation energy of 223 13 kJ/mol was derived from the formation enthalpies of diazene and hydrazine [19]. 

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