INTRAMOLECULAR ELECTRON-TRANSFER AND SN2 REACTIONS IN THE RADICAL-ANIONS OF 1-BENZOYL-OMEGA-HALOALKANE STUDIED BY PULSE-RADIOLYSIS

A one-electron reduction of 1-benzoyl-omega-haloalkane (Cl, Br, I) by solvated electrons and a subsequent intramolecular reaction of the radical anions, thus formed, have been investigated by using a pulse radiolysis technique. The reaction mechanism, electron transfer (ET) or S(N)2, and the rate constants were found to change as a function of the nature of the halide and the methylene chain length of the substrate. Although the order of reactivity based on leaving halogen atoms was I, Br, and Cl, the ease of the S(N)2 reaction was found to be in the order Cl > Br > I. In addition, the reaction rates were also affected by the polarity of the solvent used. On the basis of these results, it is discussed how the ET-S(N)2 dichotomy takes place.