Alison M. Funston and John R. Miller
Radiat. Phys. Chem., 72, 601-611 (2005). [Find paper at Elsevier Science Direct]
Abstract:
Pulse radiolysis in chlorinated hydrocarbon liquids such as
1,2-dichloroethane is a versatile and effective method for the generation of
solute radical cations. The
addition of a large concentration of toluene or benzene to solutions of
1,2-dichloroethane is found to increase the yield of solute radical cations (G
= 0.68 molecules/100 eV in 1,2-dichloroethane (Wang et al., 1979) by a factor of 2.5. The increased yield is found for
solutes which have a potential of ~ 1.1 V (vs SCE) or below for the S+·/S
couple and is due to reaction of the chlorine atom:toluene (p-Cl·)
complex with the solute; a similar species forms with benzene. p-Cl·
is formed with a yield of G = 3.0, and arises principally as a result of
geminate recombination of ions. It
has an absorption in the visible with lmax
460 nm, emax = 1800 M-1
cm-1 and decays with an observed first order rate constant k = 1.12 x 106 s-1. The rate of reaction of the p-Cl·
with added solutes ranges from 2.5 5 x 109 M-1 s-1. The other oxidant present in the
1,2-dichloroethane/toluene solutions is identified as the toluene cation
dimer. This is formed from the
1,2-dichloroethane radical cation with bimolecular rate constant k = 1.35 x 1010 M-1 s-1
with a radiation chemical yield G = 0.5.
The rate of reaction of this species with the added solutes is diffusion
controlled, k ~ 1 2 x 1010
M-1 s-1.