Hydrogen abstraction, ketones charge transfer

The second type of radical photoinitiators is the so-called bimolecular photoinitiators that consist of a diaryl ketone together with a compound that provides easily abstractable hydrogen atoms. The most common of these photoinitiators consists of benzophenone or a substituted benzophenone in combination with an aliphatic tertiary amine. A proposed mechanism for the formation of radicals by these bimolecular photoinitiators is depicted in Scheme 10. Photoexcitation of benzophenone results in the formation of triplet-state benzophenone that forms a charge transfer complex, 22, with triethanolamine. Formal electron transfer takes place with the subsequent formation of a radical cation-radical anion... 

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