Encyclopedia of Astrobiology

Living Edition
| Editors: Muriel Gargaud, William M. Irvine, Ricardo Amils, Henderson James Cleaves, Daniele Pinti, José Cernicharo Quintanilla, Michel Viso

Hydrogen Isocyanide

  • William M. Irvine
Living reference work entry
DOI: https://doi.org/10.1007/978-3-642-27833-4_1814-4




Hydrogen isocyanide (HNC) is a linear triatomic molecule that is an isomer of HCN, hydrogen cyanide, the latter being a key intermediary in several possible pathways for the production of important biological molecules. HNC itself is one of the more abundant triatomic molecular species in interstellar clouds, where the abundance ratio HNC/HCN appears to be sensitive to temperature. Because of its relatively large electric dipole moment (and hence rapid transitions to lower energy states) and since higher energy levels are populated by collisions with molecular hydrogen (the most abundant cloud species), the intensity of HNC rotational transitions can be used to estimate density in molecular clouds. Hydrogen isocyanide is also observed in cometary comae.


Hydrogen isocyanide was initially detected in the interstellar medium in 1971 by L. Snyder and D. Buhl. Because HNC is considerably higher in energy than its isomer HCN, at thermal equilibrium its...


Electric Dipole Moment Interstellar Medium Molecular Cloud Rotational Transition Abundance Ratio 
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References and Further Reading

  1. Herbst E (1987) Gas phase chemical processes in molecular clouds. In: Hollenbach DJ, Thronson HA (eds) Interstellar processes. D. Reidel, Dordrecht, pp 611–630Google Scholar
  2. Irvine WM, Bergin EA, Dickens JE, Jewitt D, Lovell AJ, Matthews HE, Schloerb FP, Senay M (1998) Chemical processing in the coma as the source of cometary HNC. Nature 393:547–550ADSCrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  1. 1.Department of AstronomyUniversity of MassachusettsAmherstUSA