SELECTIVE OXIDATION OF META-PHENYLPHENOL AND PARA-PHENYLPHENOL PHOTOSENSITIZED BY [CO(NH3)(5)N-3](2-SOLUTION() IN AQUEOUS)

The oxidation of meta-phenylphenol (m-PP) and para-phenylphenol (p-PP) was photosensitized by excitation at 365 nm in the presence of azidop entaammine cobalt(III) in neutral aqueous solution. The presence of m- PP or p-PP did not affect the initial quantum yield of cobalt(III) red uction, and oxygen had no apparent effect. By electron spin resonance spectroscopy upon irradiation, it was possible to detect the formation of both N-3(.) and m-PP. radicals as adducts with the spin trap 5,5-d imethyl-1-pyrroline-N-oxide. Laser Bash photolysis experiments gave ev idence of the formation of the corresponding phenylphenoxyl radical by reaction between N-3(.) and the phenols, and their constants of forma tion and decay were calculated. The dimers were identified as the majo r photoproducts. Trimers and tetramers of m-PP and p-PP were also form ed. It is worth noting that no formation of quinones was observed. Cob alt appeared to prevent the reaction of oxygen with the phenoxyl radic als.