Abstract: The sites of principal reactions o fthe unsaturated organic compounds——irisquinone andisopropiramfumarate with tritium gas were determined, The results showed that the reaction was principally not electrophilic addition on the carbon-carbon double bond, but the tritium incorporated by electrophilic substitution was attached to the carbon bonds. CNDO/ 2 calculations showed that the π-electron polarizability (superdelocalizability) of the reaction sites was greater than that of the carbon-carbon double bond.