ESR Spectra of Para-Substituted Alkyl- and Alkenylbenzene Radical Cations in Halocarbon Matrices

The ESR spectra of several para-substituted alkyl- and alkenylbenzene radical cations generated by 60Co γ-ray irradiation in halocarbon matrices at 77 K have been studied with the aid of semiempirical MO calculations. It has been found that the ethyl conformation of 1,4-diethylbenzene radical cation (1,4-DEB+. ) in CCl2FCClF2 is largely different from that in CCl3CF3. Further the ethyl and n-propyl groups in 4-ethyltoluene and 4-n-propyltoluene radical cations in CCl2FCClF2 take different conformations from that of 1,4-DEB +.. The conformations of the alkylbenzene radical cations depend strongly both on the matrices and on the substituent groups. A peculiar radiolytical reaction of 1,4-diisopropylbenzene to a deprotonation-type neutral radical in CCl2FCClF2 has been found, similarly to the case of photolysis.