The gas-phase reaction of the CF3 radical with thiophene

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.