Names Identifiers Preferred IUPAC name Cyano radical Systematic IUPAC name Isocyano Other names Cyanyl Nitrile CAS Number 2074-87-5 3D model (JSmol) Interactive image Beilstein Reference 1697323 ChEBI CHEBI:29306 ChemSpider 4514240 Gmelin Reference 88 PubChem CID 5359238 InChI InChI=1S/CN/c1-2 Key: JEVCWSUVFOYBFI-UHFFFAOYSA-N SMILES [C]#N Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is  ?) Infobox references

The cyanido radical (cyano is the old nomenclature) is a radical with molecular formula ·CN. The cyanido radical was one of the first detected molecules in the interstellar medium and has helped the field of astrochemistry a great deal. The first discovery was performed with a coude spectrograph which was made famous and credible due to this detection. ·CN has been observed in both diffuse clouds and dense clouds.[1] Usually, CN is detected in regions with hydrogen cyanide, hydrogen isocyanide, and HCHN+ since it is also used In the creation and destruction of these molecules.

## Physical Properties

The cyano radical is best depicted as a combination of two resonance structures: the structure with the unpaired electron on the carbon is the minor contributor, while the structure with the unpaired electron on the nitrogen (the isocyano radical) is the major contributor. The charge separation in the isocyano radical is similar to that of carbon monoxide.

·CN has a dipole moment of 1.45 Debye and a 2Σ+ ground electronic state. The selection rules are:

${\displaystyle N+S=J}$
${\displaystyle J+I=F}$

Where N is the angular momentum, S is the electric spin, and I = 1 is the nuclear spin of 14N.[2]

## Formation and destruction of ·CN

### Formation

• Dissociative Recombination In Diffuse Clouds: HCN+ + e → ·CN + ·H [1]
• Photo-Dissociation In Dense Clouds: HCN + hv → ·CN + ·H[3]

### Destruction

H3+ + ·CN → HCN+ + H2

## Detections of ·CN

·CN was first detected In 1941 by A. McKellar In the interstellar medium.[3]

The coude spectrograph and a 100-inch (2.5 m) telescope were used to observe ·CN's interstellar lines and ultraviolet spectra. Use of the spectrograph proved McKellar's findings to be correct and also made the spectrograph famous.[4] In 1970, ·CN's first rotational transition from J=0 to J=1 was detected In the Orion Nebula and W51.[5] The first detection of ·CN in extragalactic sources were seen toward Sculptor Galaxy (NGC 253), IC 342, and M82 In 1988. These emission lines seen were from N=1 to N=0 and N=2 to N=1.[6] In 1991, the ·CN vibration-rotational bands were observed in a king furnace at the National Solar Observatory using a McMath Fourier-Transform spectrometer. The observed 2 to 0 lines show an extreme hyperfine structure.[7] In 1995, the rotational absorption spectrum of ·CN in the ground state was observed in the 1 THz region, and most of the lines were measured in the range of 560 to 1020 GHz. Four new rotational transitions were measured; N=8 to N=8, J=15/2 to J=17/2 and J=17/2 to J=19/2; N=7 to N=8, J=15/2 to J=17/2 and J=13/2 to J=15/2.[8]

## References

1. ^ a b Liszt, H.; Lucas, R. (2001). "Comparative chemistry of difuse clouds" (PDF). Astronomy and Astrophysics. Astronomy and Astrophysics. 370 (2): 1–11. arXiv:astro-ph/0103247. Bibcode:2001A&A...370..576L. doi:10.1051/0004-6361:20010260. Retrieved 4 August 2009.
2. ^ Skatrud, David D.; De Lucia, Frank C.; Blake, Geoffrey A.; Sastry, K. V. L. N. (1983). "The millimeter and submillimeter spectrum of ·CN in its first four vibrational states". Journal of Molecular Spectroscopy. 99 (1): 35–46. Bibcode:1983JMoSp..99...35S. doi:10.1016/0022-2852(83)90290-4.
3. ^ a b Bakker, Eric J.; Waters, L.B.F.M.; Lamers, Henny J.G.L.M.; Trams, Norman R.; Van der Wolf, Frank L.A. (23 October 1995). "Detection of C2, CN, and NaID absorption in the AGB remnant of HD56126". Astronomy and Astrophysics. arXiv:astro-ph/9510122v1. Bibcode:1996yCat..33100893B.
4. ^ McKellar, Andrew (June 1940). "Evidence for the Molecular Origin of Some Hitherto Unidentified Interstellar Lines". Publications of the Astronomical Society of the Pacific. Publications of the Astronomical Society of the Pacific. 52 (307): 187. Bibcode:1940PASP...52..187M. doi:10.1086/125159.
5. ^ Walter S., Adams (January 1941). "Some Results with the COUDÉ Spectrograph of the Mount Wilson Observatory". The Astrophysical Journal. Astrophysical Journal. 93: 11. Bibcode:1941ApJ....93...11A. doi:10.1086/144237.
6. ^ Henkel, C.; Schilke, P.; Mauersberger, R. (July 1988). "Molecules in external galaxies - The detection of CN, C2H, and HNC, and the tentative detection of HC3N". 201 (1). Astronomy and Astrophysics: L23–L26. Bibcode:1988A&A...201L..23H.
7. ^ Jefferts, K. B.; Penzias, A. A.; Wilson, R. W. (August 1970). "Observation of the CN Radical in the Orion Nebula and W51". The Astrophysical Journal. Astrophysical Journal. 161: L87. Bibcode:1970ApJ...161L..87J. doi:10.1086/180576.
8. ^ Klisch, E.; Klaus, T.; Belov, S. P.; Winnewisser, G.; Herbst, E. (December 1995). "Laboratory rotational spectrum of CN in the 1 THz region". 304. Astronomy and Astrophysics: L5. Bibcode:1995A&A...304L...5K.