Electron Spin Resonance Studies of Elementary Processes in Radiation- and Photo-chemistry: Part 12.—Fluorinated Carboxylic Acids at Cryogenic Temperatures

Abstract

Some information concerning the mechanism of the radiolysis of perfluorinated carboxylic acids is presented from an examination of the e.s.r. spectra of radicals trapped in polycrystallinc samples of the acids between 77 and 300 K. Three types of radicals have been identified iny-irradiatcd samples of RCF2COOH (R = F, CF3, CF3CF2, C6H13, CF2COOH, CF2CF2COOH). These arc (1) parent radical anions RCF2COOH", (2) primary fluoralkyl radicals RCF2, and (3) secondary radicals RCFCOOH. The radical anions lose F~ on thermal annealing to yield additional RdFCOOH radicals, but when samples containing RCF2COOH~ are u.v.-irradiatcd at 77 K these species disappear without the appearance of any identifiable radical product, as do the corresponding species in non fluorinated carboxylic acids. The RCF2 radicals are believed to originate from the cationic species formed in the initial ionization following proton transfer and elimination of CO2.