CmHn+ reactions with H and H-2: An experimental study

We report measurements of the reactions of a number of hydrocarbon ions with atomic and molecular hydrogen made using a selected ion flow tube (SIFT) operating at room temperature. Results, including branching ratios and rate coefficients, are reported for CmHn+ ions (m = 2-6, n = 0-9). Highly unsaturated hydrocarbon ions undergo mainly H atom abstraction reactions with H-2 forming CmHn+1+ + H products. More saturated ions are unreactive. Two types of reactions occur for H atoms: H atom transfer to give CmHn-1+ + H-2 (if exothermic) and association (to give CmHn+1+).