Photoinduzierte H‐Abstraktionen an Benzylarylethern durch Benzophenon

Abstract

Photoinduced H‐Abstraction on Benzyl Aryl Ethers by Benzophenone The triplet state of benzophenone abstracts in benzene of benzyl aryl ether 6 hydrogen atom from the CH2‐group. The formed α‐ether radicals 1 and diphenylhydroxymethyl radicals 8 react to form the three possible reaction products in statistical distribution. Benzaldehydes 2 and phenols 11 are formed in a side reaction. From quantum yield measurements of the benzophenone reduction in dependence upon the concentration of benzyl phenyl ether 6a follows a rate constant of the H‐abstraction of 9.5 ·105 M−1s−1 which is in good agreement with measurements in presence of naphthalene as a quencher. The quenching constant for benzophenone triplet by naphthalene is 2 · 109 M−1s−1. For benzyl phenyl ethers substituted in the benzyl ring the reaction constant for the H‐abstraction reaction was determined, ϱ = −0,68,

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