Reactivity of HNC with Small Hydrocarbon Radicals

Abstract

We report a theoretical study of the potential energy surfaces relevant to reaction of hydrogen isocyanide (HNC) with the hydrocarbon radicals R (R = H, CH3, C2H, C2H3, C2H5). Stationary points on these surfaces have been obtained at the B3-LYP/6-311+G** level of theory; relative energies of the stationary points have been determined by implementation of the CBS-RAD “model chemistry” methodology on the B3-LYP/6-311+G** optimized geometries. Product channels considered are nitrile formation (RCN + H), R-catalyzed tautomerization (HCN + R), and, when exothermic, H-atom abstraction (RH + CN). We find that the barriers to the HCN + R channel universally exceed those for the RCN + H channel, thus effectively inhibiting the former process at low temperatures. Nevertheless (with the exception of RC2H), a moderate barrier (Ea < 35 kJ mol-1) also exists to RCN + H production. The comparatively low reactivity thus inferred for HNC, in the context of its reactions with radicals in general, is consistent with the app...