The hypothesis that the irradiation of unsaturated sultones gives the final products, the ketosulfonic esters, via a sulfene intermediate has been reexamined. In the case of sultone (4), it has been shown that, if such a species be an intermediate, it must have a lifetime, in cyclohexane solution, of less than 20 μs. The consequenes of this observation are discussed.The flashing of sultone (4) in methanol generates the enol of the keto ester end product (13) which decays with a half life of about 20 s