The rate constant of the primary decomposition step was determined for four symmetrical and four unsymmetrical azoalkanes. From the experimental activation energies and some literature enthalpy data, the following enthalpies of formation of radicals and group contributions were calculated: ΔHƒ (CH3N2) = 51.5 ± 1.8 kcal mol−1, ΔHƒ (C2H5N2) = 44.8 ± 2.5 kcal mol−1, ΔHƒ (2−C3H7N2) = 37.9 ± 2.2 kcal mol−1, [NA‐(C)] = 27.6 ± 3.7 kcal mol−1, [NA‐(ṄA) (C)] = 61.2 ± 3.1 kcal mol−1.

The thermal decomposition of azoethane (AE) was studied by detailed product analysis in the temperature and pressure intervals 508-598 K and 2.7-13.3 kPa. Besides the hydrocarbon products, three characteristic and quantitatively important nitrogen-containing compounds were also determined: ethyl-2-butyldiimide, ethanal-diethylhydrmone, and tetraethyl-hydrazine. Apart from the predominant termination reactions of the ethyl radical with itself and with the pz radical, the decomposition is characterized by a very short chain reaction. The measurements led to determination of the following rate constants and rate constant ratios: log(k,/s-') = (16.0 ? 0.2) -(207.6 t 2.0) kJ mo1-'/2.3RT

The thermal decomposition of azoisopropane (AIP) was studied by detailed product analysis in the temperature and pressure intervals 498-563 K and 0.67-5.33 kPa. Besides the predominant termination and hydrogen-abstraction reaction of the 2-propyl radical, the decomposition is characterized by a very short chain process. The following rate constants were determined from the measurements log(k,/s-') = (16.3 2 0.2) -(199.9 t 1.6) kJ mol-'/2.3RT

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