Products of the Triplet Excited State Produced in the Radiolysis of Liquid Benzene

Abstract

The radiation chemical yields of the products derived from the triplet excited state produced in the radiolysis of liquid benzene with gamma-rays, 10 MeV 4He ions, and 10 MeV 12C ions have been determined. Iodine scavenging techniques have been used to examine the formation and role of radicals, especially the H atom and phenyl radical. For all irradiation types examined here, the increase in hydrogen iodide yields with increasing iodine concentration matches the increase in iodobenzene yields. This agreement suggests that the benzene triplet excited state is the common precursor for the H atom and the phenyl radical. Pulse radiolysis studies in liquid benzene have determined the rate coefficients for the reactions of phenyl radicals with iodine and with the solvent benzene to be 9.3 x 10(9) M(-1) s(-1) and 3.1 x 10(5) M(-1) s(-1), respectively. Direct measurements of polymer formation, which refers to trimers (C18) and higher order compounds (>C18), in liquid benzene radiolysis using gamma-rays, 4He ions, and 12C ions at relatively high doses have been performed using gel permeation chromatography. The yields of trimers increase from gamma-rays to 12C ions due to the increased importance of intratrack radical-radical reactions that can be scavenged by the radical scavenging reactions of iodine. On the other hand, the >C18 product yields decrease from gamma-rays to 12C ions. The structure of the polymer consists of a partly saturated ring as determined by infrared and gas chromatography/mass spectrometry studies. A schematic representation for the radiolytic decomposition of the benzene triplet excited state is presented.

Growth of polyphenyls via ion–molecule reactions: An experimental and theoretical mechanistic study

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Radical yields in the radiolysis of cyclic compounds

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Radiation-Induced Transformations of C6H6 Molecules in Solid Noble-Gas Matrices: Is Benzene Intrinsically Resistant in Condensed Media?

“…Indeed, based on the scavenging experiments, Enomoto et al have concluded that triplet excited states are the precursors of phenyl radicals under radiolysis of liquid benzene. 38 If we consider the excited states resulting from ion−electron recombination, formation of triplet states (including both T 1 and higher triplets) is quite probable, and the ratio of triplet to singlet states should be 3:1 for recombination of noncorrelated pairs. The loss of spin correlation in recombining pairs is expected because both positive holes and electrons travel over large distance in solid noble-gas matrices.…”