The anionic, neutral, and cationic [H,C-2,N] potential energy hypersurfaces have been explored by means of mass spectrometric experiments and by density functional theory/Hartree-Fock hybrid computations. Three distinct neutral isomers can be characterized in the gas phase : the well-known cyanocarbene HCCN, the as yet unknown isocyanocarbene HCNC, and also the recently observed iminovinylidene HNCC. Calculations of the minima, the transition structures for interconversions, and the dissociation channels were performed in order to rationalize the experimental results. The B3LYP method is demonstrated to give results which are in very good agreement with CCSD(T) calculations.