Odd-Even Reactivity Variation Due to Dynamical Effects around the Roaming Saddle Points of the Reaction Between C n- Chain ( n = 2-8) and H2.

Unsaturated carbon cluster chains often have chemical properties depending on the cluster size. While carbon cluster cation chains show odd-even variation in the reactivity with hydrogen, the chemistry of the carbon anion chain has been poorly understood even for the bimolecular reaction with hydrogen. We present a systematic theoretical study based on transition state calculations and molecular dynamics trajectory simulations for the reaction of C n- ( n = 2-8) + H2. We show that carbon cluster chain anion also has an odd-even variation in reactivity where the even ones are more reactive. In addition, dynamics trajectory shows that while odd n only resulted in the C nH2- product with direct H insertion similar to the static reaction pathway, even n had a more complex product branching producing not only C nH2- but also C nH- + H and HC nH- with the roaming of an H atom. The flexibility of the carbon's valence electrons plays an important role to form different isomers of the double H adducts HC nH- and C nH2- from the roaming condition.