Electron spin resonance and molecular orbital study of radicals in irradiated fluoro-derivatives

Abstract

The low temperature matrix isolation technique coupled with e.s.r. spectrometry was employed to study the radicals produced by low temperature irradiation by a ⁶⁰Co source of a number of fluoro and fluoro-chloro derivatives including chloroformyl- and fluoroformyl-perfluoropolyethers, trichlorofluoromethane, 1,1,2-trichloro-1,2,2-trifluoroethane, and perfluoro-1-methyldecalin (PFMD). The major radiolysis process in the acyl chloride is thought to be dissociative electron capture with formation of acyl radicals; the splitting of the C–O bonds in the chains is also inferred from the identification of RR′CF· and RCF₂· species. In the acyl fluoride direct splitting of the COF group is also assumed to take place in order to explain the higher relative yield (with respect to the acyl chloride) of RCF₂·. The irradiation of PFMD yields RR′CF· and RCF₂· at low temperature and the 1-perfluoro-1-methyldecalin-8a-yl radical after warming above 160–180 K. This radical has a spectrum which is consistent with an average planar configuration at C-8a. By irradiation of CFCl₃ and CF₂ClCFCl₂(thiourea clathrate)·CFCl₂ and CF₂ClĊFCl were obtained; the structure and conformation of these radicals have been investigated by the CNDO/2 MO method.