Photochemistry of dialkylphenacylsulfonium salts

Several reports of the photolysis of dialkylphenacylsulfonium salts appear in the literature Qjj basis of the results of product studies after long irradiation 

Quantum yield measurements of the photolysis of phenacyltetramethylenesulfonium BFT and AsFg in DMSO-dg at 313 nm gave values of 0.32 and 0.42, respectively These values are shomewhat higher than those obtained for the corresponding triphenylsulfonium salts ( diphenylsulfide = 0.1-0.2) at the same wavelength and are probably solvent dependent. 

Determined in DMSO-d with 300 nm light at a constant intensity of approximately 1.38 X 10 einsteins  

Modifications at other sites in the dialkylphenacylsulfonium salt molecule have less pronounced effects on the photolysis rates. In general, substituents other than hydrogen on the carbon adjacent to the carbonyl tend to slightly accelerate or decelerate the rate due to a balance in steric and electronic effects. Similarly, the highest photolysis rates were obtained when the dialkyl groups were both methyls which conformationally and sterically favor the six member transition state of the Norrish Type II reaction. 

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