Thiophosphonyl Radicals Photolytic Generation and Reactivity Towards Olefinic Compounds

Upon irradiation with UV light (λ = 347 nm), 2,4,6-trimethylbenzoyldiphenylphosphine sulfide was found to be fragmented into free radicals by α-scission (F(k) = 0.3 ± 0.1): Flash photolysis studies revealed that the optical absorption spectrum of diphenylthiophosphonyl radicals, S = P(Ph) 2 . possesses a strong band with λ max = 340 nm and a somewhat weaker band with λ max ≈ 500 nm (e 340nm = 1.2 ± 0.2) · 10 4 1/mol cm). The reactivity towards olefinic compounds, M, is 10 to 30 times lower than in the case of O = P(Ph) 2 radicals. Typical bimolecular rate constants (in 1/mol s) of the reaction of S = P(Ph) 2 with M are: 4 x 10 6 (styrene), 6.2 x 10 5 (methylacrylate), 4.2 x 10 4 (vinyl acetate).