The mechanisms of the C+HNC, N+C2H, H+C2N and H+CNC reactions have been investigated using ab initio and OFT calculations. The long-range interactions and species involved in these systems on the triplet potential energy surface were optimized at the M06-2X/cc-pVQZ, MRCI+Q/aug-cc-pVTZ and CCSD(T)/aug-cc-pVQZ levels. The calculations show that these reactions proceed without a barrier in the entrance valley, and are mostly characterized by transition states which are submerged with respect to the reagent level. As a result, these processes are potentially very important for interstellar chemistry. (C) 2015 Elsevier B.V. All rights reserved.