Kinetic Study for Reactions of Phenylseleno Radical with Vinyl Monomers

Article abstract of DOI:10.1021/ja00342a034

The reactivities of the phenylseleno radical (PheSe.) generated by flash photolysis of diphenyl diselenide have been determined.Low reactivities of PhSe. toward oxygen, hydrogen -atom donors, and halogen-atom donors have been confirmed.With vinyl monomers (CH2=CHY) PhSe. reacts in a reversible fashion; by the addition of oxygen as a selective radical trap to the adduct radicals (PhSeCH2C.HY), the absolute addition rate constants have been determined.The reverse rate constants and the equilibrium constants have been estimated as relative ones from which the thermodynamic stabilities of the adduct radicals have been elucidated.The addition rates increase mainly with the stabilities of the adduct radicals and subsequently with the polar nature of the transition state.The lower reactivity of PhSe. compared with the phenylthio radical (PhS.) is attributed to the greater stabilization of an unpaired electron in PhSe. than that in PhS..