Ionic condensation of olefins by ionizing radiation. Effects of additives and the detailed mechanism

Abstract

The mechanism of olefin condensation initiated by the radical ion, C_nH⁺_2n, is further supported by studies of the effects of additives on 1-pentene radiolysis. Radical scavengers inhibit formation of all of the dimeric products except 3-decene, formed with a G-value of 0.55. Electron scavengers in concentrations as low as 0.02 M increase this G-value up to a factor of 3; it is believed they interfere with ion-electron recombination and increase the ion lifetime. Proton scavengers and certain unsaturated additives at about 1 M reduce the G-value by competitive reactions with the olefin ion. Structures of the straight-chain ionic dimer indicate that ionic dimerization proceeds with carbon-carbon bond formation between terminal carbons, with a single hydride migration of an originally allylic hydrogen. Condensation to form trimer and higher polymers requires development of branching.