A. Albini et al., THE PHOTOREDUCTION OF 3-BENZOYLPYRIDINE - AN EXPERIMENTAL AND THEORETICAL-STUDY OF THE FORMATION OF THE INTERMEDIATE LAT, Perkin transactions. 2, (4), 1993, pp. 691-695
3-Benzoylpyridine (3-BPy) triplet abstracts hydrogen from alcohols to
give a ketyl radical similar in its properties to that of benzophenone
. In neat isopropanol, the main product of the ketyl radical reactions
is the pinacol while in water-isopropanol mixed solvent a 'light abso
rbing transient' (LAT) accumulates. This is much more stable than the
LAT formed by photolysis of benzophenone and results from the coupling
of two 3-BPy ketyl radicals, with attack of one of them on the 6 posi
tion of the pyridine ring of the other. Chemical evolution of this int
ermediate leads in part to an oxidized product conserving the same ske
leton. Theoretical calculations and transient absorption spectroscopy
support the structure of the intermediate and the proposed mechanism o
f reaction.