Formation of 3-aminophenoxazone complex by photoreaction

Abstract

Photochemical oxidation of o-aminophenol was carried out in 30% ethanol or 30% dioxan solution and changes during this reaction were followed by polarography and electron absorption spectrum. Irradiation of 30% dioxan solution of o-aminophenol over a long time resulted in the appearance of a wave (E1/2=-0.85V) for separation of hydrogen peroxide, besides the reduction wave (E1/2=-0.5V) of 3-aminophenoxazone and that (E<1/2>=-1.2V) of hydrogen peroxide seen at the time of short irradiation. Oxidation products were obtained as two kinds of crystals ; crystal 1 of red needles, mp 250-251°, corresponding to 3-aminophenoxazone, and crystal 2 of deep reddish purple needles, mp 260-261°, which was found to contain 50% of 3-aminophenoxazone from the comparison of polarographic reduction wave height and E<425> nm. Since the electron spin resonance spectrum of crystal 2 was similar to that of quinhydrone, it was concluded that this product is a 1 : 1 complex of 3-aminophenoxazone and 3-hydroxy-3-aminophenoxazine.