A theoretical investigation of the reactions of n(2D) with Small Alkynes and Implications for the Prebiotic Chemistry of Titan

The reactions between atomic nitrogen, in its first electronically excited state (2D), and two different hydrocarbons, methyl acetylene and acetylene, have been analyzed by performing electronic structure calculations of the potential energy surface. For each reaction, H-displacement channels leading to cyclic molecular products have been identified, together with an H2 elimination channel for the reaction N(2D) + acetylene and a methyl (CH3) loss channel for the N(2D) + methylacetylene reaction. Since both reactions have been found to be exothermic and without an entrance barrier, we suggest that they are fast and efficient under the conditions of the upper atmosphere of Titan. These data will be used to perform kinetic calculations and will be compared with detailed experimental results in future work.