Gas-phase reactions of halogenated radical carbene anions with sulfur and oxygen containing species

The reactivities of mono- and dihalocarbene anions (CHCl−, CHBr−, CF2−, CCl2−, and CBrCl−) were studied using a tandem flowing afterglow-selected ion flow tube instrument. Reaction rate constants and product branching ratios are reported for the reactions of these carbene anions with six neutral reagents (CS2, COS, CO2, O2, CO, and N2O). These anions were found to demonstrate diverse chemistry as illustrated by formation of multiple product ions and by the observed reaction trends. The reactions of CHCl− and CHBr− occur with similar efficiencies and reactivity patterns. Substitution of a Cl atom for an H atom to form CCl2− and CBrCl− decreases the rate constants; these two anions react with similar efficiencies and reactivity trends. The CF2− anion displays remarkably different reactivity; these differences are discussed in terms of its lower electron binding energy and the effect of the electronegative fluorine substituents. The results presented here are compared to the reactivity of the CH2− anion, which has previously been reported.