The gas-phase reaction of the CF3 radical with thiophene

Abstract

The reaction of CF3 radicals, generated by photolysis of CF3I or hexafluoroacetone with thiophene, was studied in the gas phase at 25 °C. At conversion of thiophene less than 20%, monosubstituted CF3-thiophenes were found as the main reaction products, in addition to CF3H, C2F6, and monosubstituted dihydro-CF3-thiophene, the latter in very low proportion. An isomeric mixture of 2- and 3-CF3-thiophene was obtained in a ratio of about 16, independent of the radical source used (CF3I or hexafluoroacetone) to produce the CF3 radicals. A plausible mechanism that accounts for the observed products is proposed, and the reactivity of thiophene toward the CF3 radical at 25 °C was determined as kadd/kc1/2 = 106 ± 4 cm3/2 mol–1/2 s–1/2.Key words: thiophene, trifluoromethyl radical, reaction mechanism, reactivity.