Electron spin resonance studies of the free radicals derived from tetraphenylhydrazine

Abstract

The free radicals obtained from tetraphenylhydrazine, diphenylbenzidine and diphenylamine under different conditions have been investigated with electron spin resonance techniques. The identification and differentiation between the radicals were done on the basis of their g-values and the line-widths and hyperfine structure exhibited by their spectra. The formation of the diphenylamino radical, by the thermal dissociation of tetraphenylhydrazine in non-polar solvents has been confirmed. The same radical is obtained when tetraphenylhydrazine is subjected to atmospheric oxidation in a non-polar solvent. The tetraphenylhydrazinium radical ion, is formed (1) when a solution of tetraphenyl-hydrazine in acetic acid is subjected to prolonged atmospheric oxidation, (2) when a similar, freshly prepared solution is heated and (3) when diphenylamine or diphenylbenzidine is subjected to oxidation in an acetic acid medium. It is believed that the protonated hydrazinium radical, results if an acetic acid solution of tetraphenylhydrazine is treated with a few drops of concentrated sulphuric acid. During the course of this investigation, the g-value of a 0·002 M solution of DPPH in xylene was measured to be 2·00347±0·00004.