PHOTOLYSIS OF 1-ARYL-3,3-DIALKYLTRIAZENES

The photolytic decomposition of substituted 1-phenyl-3,3-diethyl-triaz enes has been studied using both pulsed XeCl excimer excitation at 30 8 nm, and continuous-wave irradiation with a xenon lamp. Electron-with drawing substituents in the para position at the phenyl ring are found to decrease both the quantum yield of photolysis and the apparent fir st-order rate constant of decomposition. The reaction proceeds accordi ng to an overall one-step pathway; analysis of the photolysis products by gas chromatography-mass spectrometry is consistent with a radical decomposition mechanism. For the compound 1-(4-nitrophenyl)-3,3-diethy l-triazene, an autocatalytic acceleration of the photolysis was observ ed during the continuous-wave irradiation, using a xenon lamp source. This phenomenon is analysed in terms of an involvement of the nitro gr oup: photoreduction of the latter functionality involves the creation of solvent radicals in comparatively large concentrations, which are d etected by in-situ electron spin resonance experiments. These radicals may attack and decompose further molecules of the starting material.