Flash photolysis studies of benzophenone in ethanol

We report the results of a flash photolysis study of solutions of benzophenone in ethanol. In the wavelength range 350 to 650 nm two transient absorbing species were detected. One of these species was the ketyl radical whilst the other was a stable intermediate (in the absence of O2) which has been reported previously, but has yet remained unidentified. A kinetic analysis showed that the intermediate built up by a second order process at the same rate as the ketyl radical decayed. It was concluded that the intermediate was isobenzopinacol formed by dimerization of the ketyl radical.