Abstract Quantum chemistry calculations at the MP2 and MRCI levels have been used to compute the energies of the stationary points and the minimum energy pathways (MEPs) between them for the dissociation and isomerization reactions of the methylene amido-gene radical. The MEPs for H2CN → trans-HCNH → cis-HCNH, H2CN → H + HCN, cis-HCNH → H + {HCN, HNC}, trans-HCNH → H + {HCN, HNC} and collinear CN + H2 → HCN + H are reported. The absence of a transition state for the dissociation of the trans isomer has been verified. Also, some calculations for the concerted H2CN ↔ H2 + CN are reported.