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

Abstract

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 n H2 – product with direct H insertion similar to the static reaction pathway, even n had a more complex product branching producing not only C n H2 – but also C n H– + H and HC n H– 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 n H– and C n H2 – from the roaming condition.