Reactions of Azo-, Diazo-, and Related Compounds

The thermolysis and photolysis of azo-compounds (R. N N. R) are well documented sources of radicals (for a review, see Strausz et al., 1972). As such they have been extensively used as radical sources in CIDNP studies (Fischer and Bargon, 1969 Gloss and Trifunac, 1969, 1970b, c Iwamura and Iwaraura, 1970 Iwamura et al., 1970b Kasukhin aZ., 1970). The application of CIDNP to unravel some of the mechanistic complexities of the decomposition of azo-compounds has now begun. 

A central problem in this area concerns the timing of the cleavage of the two carbon-nitrogen bonds. Synchronous and consecutive cleavage can be envisaged [equation (46)] and conventional studies of kinetics and 

Photolysis at about 40°C of the Zraws-isomer of the unsymmetrical azo-compound 4 in benzene solution yields dicumyl and biphenyl as the major products, together with a little a-raethylstyrene, cumene, and 2,2-diphenylpropane. All these products show polarization of their 

Diazenyl radicals have also been detected in related systems. The rapid rearrangement of 1,3,5-triarylpentazadienes [equation (47)] involves intermediate triazenyl-diazenyl radical pairs, as indicated by the appearance in emission of the n.m.r. transitions of the -methyl protons of the starting material when Ar = Ar =p-CH3.C6H4 (Hol-laender and Neumann, 1970). The weak emission of benzene which accompanies a much more intense emission due to toluene when the 1,3-diaryltetrazene 6 decomposes in acetone at 50° has been interpreted 

In the stepwise decomposition of azo-compounds such as 4, products can arise from reactions within the primary diazenyl-alkyl radical pair or from the secondary radical pair produced by loss of nitrogen from the 

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