Lichtinitiierte Polymer‐ und Polymerisationsreaktionen. III. Photoinduzierte Zersetzung von Aryldiazoniumsalzen durch Benzoinderivate

Light Induced Polymer and Polymerization Reactions. III. Photoinduced Decomposition of Arene Diazonium Salts by Benzoin Derivatives The combination benzoin derivate/arene diazonium salt is suitable as a bivalent photoinitiator system for radicalic and cationic photopolymerization. By means of product analysis, quantum yield measurements and photo‐CIDNP‐studies a mechanism was proposed including the electron transfer from α‐substituted benzyl radicals formed by benzoin derivate photolysis to arene diazonium salts. The quantum yields for diazonium salt decomposition in acetonitril were about 0.65. They show only a small dependence on substituents of diazonium salt but are strong influenced by the solvent. In methanol or dioxane quantum yields were found from 11 to 460. 13C‐photo‐CIDNP‐measurements agree with a mechanism of benzoin ether photolysis on the triplet state.