Photoinitiators and photoinitiation, 12. The aromatic ketone/t-amine Type-II photoinitiating system. Identification of the initiating species†

The system benzophenone/N,N-dimethylaniline (DMA) representing a typical Type-II photoinitiating system is irradiated in the presence of 1,1-di(p-tolyl)ethylene (DTE) as a non-polymerising model substrate. In the presence of DMA the excited triplet state of benzophenone is not quenched by DTE and N-[3,3-di(p-tolyl)propyl]-N-methylaniline is isolated as the major product, indicating the DMA derived radical as the main initiating species in such Type-II systems. The mechanism of the reaction and its implications are discussed.