Photoinitiators and photoinitiation. Part 13. The photodecomposition of sulphonic esters of α-hydroxymethylbenzoin ethers

Abstract The photodecomposition of some sulphonic esters of α -hydroxymethylbenzoin ethers is examined using ESR and radical trappingtechniques. Photoinduced α -cleavage into benzoyl and α -alkoxy- α -sulphonyloxymethylbenzyl radicals from a short-lived triplet excited state is observed. The α , α -disubstituted benzyl radicals undergo subsequent fragmentation, generating benzoylmethylradicals and sulphonic acids at a rate k el 7 s −1 . The fate of the alkyl ether part of the α,α-disubstituted benzyl radicals after elimination of sulphonic acid is unknown at present.