THE H2CN+ molecular ion is generally agreed1–4 to have a critical role in the formation of interstellar HCN and HNC. The obvious problem that H2CN+ has not yet been identified in interstellar space is complicated by considerable uncertainty due to the possible existence of three distinct isomers of H2CN+, with nuclear arrangements Brown4 stated that although the third isomer had been completely neglected in previous discussion, it is likely to have a crucial role in the formation of HNC. Brown also notes that the linear isomer, which is isoelectronic with acetylene and thus expected to lie lowest of all the isomers of H2CN+, may play no part at all in the formation of either HCN or HNC. This is from the hypothesis that the sequence thought most likely to lead to HCN is orfollowed by dissociative recombinationBrown argues that the formation of the more stable linear isomer (1) would require the migration of a hydrogen atom from carbon to nitrogen. As this migration is expected to be very costly energetically, the H2CN+ on the right hand side of reactions (4) and (5) should be the isomer (2) above. Similarly, he argues that the sequence leading to HNC should exclusively involve isomer (3). We report here theoretical studies designed to investigate the molecular structure of (3) and its energy relative to the previously studied3 isomers (1) and (2). In addition, because reactions (4), (5) and (7) must be exothermic or very nearly so if they play a part in the interstellar medium, this question has also been assessed.
This is a preview of subscription content, access via your institution
Subscribe to Journal
Get full journal access for 1 year
only $3.90 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Tax calculation will be finalised during checkout.
Get time limited or full article access on ReadCube.
All prices are NET prices.
Herbst, E. & Klemperer, W. Astrophys. J. 185, 505 (1973).
Watson, W. D. Astrophys. J. Lett. 183, L17 (1973).
Pearson, P. K. & Schaefer, H. F. Astrophys. J. 192, 33 (1974).
Brown, R. D. Nature 270, 39 (1977).
Dunning, T. H. J. chem. Phys. 53, 2823 (1970).
Schaefer, H. F. The Electronic Structure of Atoms and Molecules: A Survey of Rigorous Quantum Mechanical Results (Addison-Wesley, Reading, Massachusetts, 1972).
Pulay, P. in Modern Theoretical Chemistry, Vol. 4 (ed. Schaefer, H. F.) (Plenum, New York, 1977).
Lucchese, R. R. & Schaefer, H. F. J. chem. Phys. 68, 769 (1978).
Liddy, J. P., Freeman, C. G. & McEwan, M. J. Mon. Not. R. astr. Soc. 180, 683 (1977).
JANAF Thermochemical Tables, 2nd edn (NBS Washington, D.C., 1971).
Herzberg, G. Electronic Spectra of Polyatomic Molecules (Van Nostrand Reinhold, New York, 1966).
Moore, C. E. Atomic Energy Levels (NBS Washington, D.C., 1949).
Wolf, J. F. et al. J. Am. chem. Soc. 99, 5417 (1977).
Smith, D. & Adam, N. G. Chem. phys. Lett. 47, 145 (1977).
Fehsenfeld, F. C. Astrophys. J. 209, 638 (1976).
About this article
Cite this article
CONRAD, M., SCHAEFER, H. Role of different isomers of the H2CN+ ion in the formation of interstellar HCN and HNC. Nature 274, 456–457 (1978). https://doi.org/10.1038/274456a0