INVESTIGATION OF THE DECOMPOSITION OF COMPOUNDS CONTAINING AZO GROUPSBY EPR SPECTROSCOPY

In photochemically, electrochemically and thermally initiated decompos ition, compounds containing the azo group ((RN)-R-1=(NR)-R-2) usually form reactive, short-lived radicals R-1(.) and R-2(.) which correspond s to synchronous splitting. As examples, aliphatic azo compounds, 1-ar yl-2-alkylazo compounds, azophosphonates, azosulfonates, azosulfones, azosulfides, triazenes, pentazadienes, hexazadienes, acyl- and diacyla zo compounds, diazonium salts and cyclic azo compounds have been studi ed. R-1(.) and R-2(.) Were characterized by means of the EPR spin trap technique. These reactive radicals may abstract hydrogen from the sol vent or any neighborhood functions, or dimerize (R-1-R-2). Some azo co mpounds trap R-1(.) and R-2(.) and thus form the corresponding hydrazy l radicals. In cathodic reduction, prior to the initiation of decompos ition, corresponding anion radicals centered on the azo group were obs erved which have considerable stability if R-1 and R-2 are conjugated structures. (C) 1998 John Wiley & Sons, Ltd.