Abstract: Photolysis of alkylmercury halides in the presence of electronegatively-substituted 1-alkenes yields adduct radicals [RCHzCH (EWG)'] that in some cases react with RHgX to form RCHzCH (HgX)(EWG), eg, EWG=(Et0) 2PO or PhS02. When the EWG is carbonyl or cyano, the resonance stabilized adduct radicals fail to react with the alkyl mercury halide. In these cases photolysis with RHgCLKI in MezSO leads to the adduct mercurial via reaction ...