Photoinduced reaction. 142. Intramolecular hydrogen abstraction from triplet states of 2,4,6-triisopropylbenzophenones: importance of hindered rotation in excited states
Steric and substituenteffects on the photochemical reaction of 2,4,6-trialkylphenyl ketones has been investigated. A striking steric effect was observed in the photoreaction of 2,4,6-trialkylbenzophenones. The more hindered the carbonyl group, the more readily photoenolization occurs resulting in intramolecular cyclization leading to benzocyclobutenol derivatives. With 2,4,6-trialkylacetophenones
Substituted benzophenones and their liquid mixtures suitable for use as photopolymerisation initiators
申请人:FRATELLI LAMBERTI S.p.A.
公开号:EP0209831A2
公开(公告)日:1987-01-28
As initiators for the photopolymerisation of ethylenically unsaturated compounds, the use of systems consisting of compounds of benzophenone type of formula I
In which R, R' and R2 are preferably alkyls of 1-4 carbon atoms, R3 and R4 are preferably hydrogen and Ar is preferably phenyl, in combination with donors of hydrogen or substances which determine the formation of labile photochemical complexes, such as alcohols, ethers and tertiary amines with hydrogens in the alpha position, and the use for the same purpose of mixtures of 2,4,6- trialkylbenzophenones and benzophenone and particularly of a mixture of 2,4,6-trimethylbenzophenone and benzophenone in a molar ratio of 1.155, which has the advantage of being liquid at temperatures exceeding 10°C and of possessing photochemical activity superior to that of benzophenone.