Photodecarboxylation of carboxylic acids sensitized by triplet benzophenone and duroquinone. A flash photolysis electron spin resonance and chemically induced dynamic nuclear polarization nuclear magnetic resonance investigation

Abstract

E.s.r. and CIDNP n.m.r. spectroscopy have been used to provide direct evidence for the mediation of R¹XCH₂· and other radicals in the decarboxylation of substituted carboxylic acids R¹XCH₂CO₂H photosensitized by carbonyl compounds. In some systems there is evidence for scavenging of R¹XCH₂· radicals by sensitizer, and it is suggested that the rates of these scavenging reactions are greatly enhanced by polar interactions between radical (acting as an electron donor) and carbonyl compound (an electron acceptor).