CHEMISTRY OF DIARYLAZOALKANES .3. EFFECT OF STRUCTURAL VARIATION ON RATE AND NATURE OF THERMAL DECOMPOSITION

A kinetic study of the thermal decomposition in toluene of various diarylazoalkanes [p,p′-difluoro-, p,p′-dichloro-, and m,m′-dichloroazocumenes and 1,1′-di(4-tolyl)azocyclohexane] showed that the rates were all first order. The effects of the structural variations were small but significant. The influence of substituents on the aromatic nucleus is discussed in terms of resonance and induction theory. A steric argument is used to rationalize the rate increase produced by changing the alkyl substituents on the side chain from dimethyl to pentamethylene. The radicals formed in the azo decompositions primarily coupled to form the expected dimers, with disproportionation occurring to a small extent. Activation energies for the thermal decompositions were determined. © 1969, American Chemical Society. All rights reserved.