View source for Chemistry:Cyano radical

{{Chembox
| Watchedfields  = changed
| verifiedrevid  = 460109140
| Name           = 
| ImageFile      = cyano radical.svg
| ImageFile1     = Cyano-radical-3D-vdW.svg
| ImageSize      = 80px
| ImageName      = Structural formula of a minor contributor to cyano radical
| PIN            = Azanylidynemethyl
| OtherNames     = Cyanyl<br />Nitrile<br />Cyano<br />Isocyano
| IUPACName      = 
| Section1       = {{Chembox Identifiers
| CASNo = 2074-87-5
| CASNo_Ref = {{cascite|correct|CAS}}
| PubChem = 5359238
| ChemSpiderID = 4514240
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 29306
| SMILES = [C]#N
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/CN/c1-2
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = JEVCWSUVFOYBFI-UHFFFAOYSA-N
| Beilstein = 1697323
| Gmelin = 88}}
| Section2       = 
| Section3       = 
| Section4       = 
| Section5       = 
| Section6       = 
}}

The '''cyano radical''' (or '''cyanido radical''') is a [[Biology:Radical|radical]] with molecular formula CN, sometimes written <sup>•</sup>CN. The cyano radical was one of the first detected molecules in the [[Astronomy:Interstellar medium|interstellar medium]], in 1938. Its detection and analysis was influential in [[Chemistry:Astrochemistry|astrochemistry]]. The discovery was confirmed with a [[Astronomy:Reflecting telescope#Coudé|coudé]] [[Astronomy:Spectrograph|spectrograph]], which was made famous and credible due to this detection. ·CN has been observed in both diffuse clouds and dense clouds.<ref name="Comparative">{{Cite journal |last1=Liszt |first1=H. |last2=Lucas |first2=R. |date=2001 |title=Comparative chemistry of diffuse clouds: II. CN, HCN, HNC, CH<sub>3</sub>CN & N<sub>2</sub>H<sup>+</sup> |journal=Astronomy & Astrophysics |volume=370 |issue=2 |pages=576–585 |bibcode=2001A&A...370..576L |bibcode-access=free |doi=10.1051/0004-6361:20010260 |arxiv=astro-ph/0103247  |doi-access=free}}</ref> Usually, CN is detected in regions with [[Chemistry:Hydrogen cyanide|hydrogen cyanide]], [[Chemistry:Hydrogen isocyanide|hydrogen isocyanide]], and [[Chemistry:HCNH+|HCNH<sup>+</sup>]], since it is involved in the creation and destruction of these species (see also ''[[Chemistry:Cyanogen|Cyanogen]]'').

==Physical Properties==
Bonding in the cyano radical can be described 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 [[Chemistry:Carbon monoxide|carbon monoxide]]. <sup>•</sup>CN has a dipole moment of 1.45&nbsp;debyes and a <sup>2</sup>Σ<sup>+</sup> ground electronic state. The [[Physics:Selection rule|selection rule]]s are:

:<math>\begin{align} N + S &= J \\ J + I &= F \end{align}</math>

where ''N'' is the [[Physics:Angular momentum|angular momentum]], ''S'' is the electric spin, and {{mvar|I}}&nbsp;=&nbsp;1 is the nuclear spin of <sup>14</sup>N.<ref>{{Cite journal |last1=Skatrud |first1=David D. |last2=De Lucia |first2=Frank C. |last3=Blake |first3=Geoffrey A. |last4=Sastry |first4=K. V. L. N. |date=1983 |title=The millimeter and submillimeter spectrum of CN in its first four vibrational states |journal=[[Physics:Journal of Molecular Spectroscopy|Journal of Molecular Spectroscopy]] |volume=99 |issue=1 |pages=35–46 |bibcode=1983JMoSp..99...35S |doi=10.1016/0022-2852(83)90290-4}}<!--| accessdate=19 December 2019 --></ref>

==Formation and destruction of <sup>•</sup>CN==

===Formation===
*Dissociative recombination in diffuse clouds''':<ref name="Comparative"/>
*:HCN<sup>+</sup> + e<sup>−</sup> → <sup>•</sup>CN + H<sup>•</sup>
*Photodissociation in dense clouds:<ref name="HD56126">{{Cite journal |last1=Bakker |first1=Eric J. |last2=Waters |first2=L. B. F. M. |last3=Lamers |first3=Henry J. G. L. M. |last4=Trams |first4=Norman R. |last5=Van der Wolf |first5=Frank L. A. |date=1996 |title=Detection of C<sub>2</sub>, CN, and NaI D absorption in the AGB remnant of HD 56126 |journal=Astronomy and Astrophysics |volume=310 |pages=893–907 |arxiv=astro-ph/9510122 |bibcode=1996A&A...310..893B |bibcode-access=free}}</ref>
*:HCN + ''hν'' → <sup>•</sup>CN + H<sup>•</sup>

===Destruction===
:{{chem|H|3|+}} + <sup>•</sup>CN → HCN + H<sub>2</sub>

==Detections of <sup>•</sup>CN==
A spectral line of <sup>•</sup>CN was detected in 1938 in the [[Astronomy:Interstellar medium|interstellar medium]] in the [[Physics:Ultraviolet|ultraviolet]], and was identified in 1940 by Andrew McKellar. The coudé spectrograph and a {{convert|100|in|m|adj=on}} telescope were used to observe <sup>•</sup>CN's interstellar lines and ultraviolet spectra. Use of the spectrograph confirmed McKellar's findings and also made the spectrograph famous.<ref>{{Cite journal |last1=McKellar |first1=Andrew |date=1940 |title=Evidence for the molecular origin of some hitherto unidentified interstellar lines |journal=Publications of the Astronomical Society of the Pacific |volume=52 |issue=307 |pages=187–192 |bibcode=1940PASP...52..187M |bibcode-access=free|doi=10.1086/125159 |doi-access=}}</ref><ref>{{Cite journal |last=Adams |first=Walter S. |date=1941 |title=Some results with the coudé spectrograph of the Mount Wilson Observatory |journal=[[Astronomy:The Astrophysical Journal|The Astrophysical Journal]] |volume=93 |pages=11–23 |bibcode=1941ApJ....93...11A |bibcode-access=free |doi=10.1086/144237 |doi-access=}}</ref> In 1970, <sup>•</sup>CN's first rotational transition from ''J''&nbsp;=&nbsp;0 to ''J''&nbsp;=&nbsp;1 was detected In the Orion Nebula and the W51 nebula.<ref name=Orion/> The first detection of <sup>•</sup>CN in extragalactic sources were seen toward [[Astronomy:Sculptor Galaxy|Sculptor Galaxy]] (NGC 253), [[Astronomy:IC 342|IC 342]], and [[Astronomy:Messier 82|M82]] In 1988. These emission lines seen were from ''N''&nbsp;=&nbsp;1 to ''N''&nbsp;=&nbsp;0 and ''N''&nbsp;=&nbsp;2 to ''N''&nbsp;=&nbsp;1.<ref>{{Cite journal |last1=Henkel |first1=C. |last2=Mauersberger |first2=R. |last3=Schilke |first3=P. |date=1988 |title=Molecules in external galaxies: The detection of CN, C<sub>2</sub>H, and HNC, and the tentative detection of HC<sub>3</sub>N |journal=Astronomy and Astrophysics |volume=201 |pages=L23–L26 |bibcode=1988A&A...201L..23H |bibcode-access=free}}</ref> In 1991, the <sup>•</sup>CN vibration-rotational bands were observed in a king furnace at the [[Organization:National Solar Observatory|National Solar Observatory]] using a McMath Fourier-Transform spectrometer. The observed 2 to 0 lines show an extreme [[Physics:Hyperfine structure|hyperfine structure]].<ref name=Orion>{{Cite journal |last1=Jefferts |first1=K. B. |last2=Penzias |first2=A. A. |last3=Wilson |first3=R. W. |date=1970 |title=Observation of the CN radical in the Orion Nebula and W51 |journal=The Astrophysical Journal |volume=161 |issue=2 |pages=L87–L89 |bibcode=1970ApJ...161L..87J |bibcode-access=free |doi=10.1086/180576 |doi-access=}}</ref> 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&nbsp;GHz. Four new rotational transitions were measured; ''N''&nbsp;=&nbsp;8 to ''N''&nbsp;=&nbsp;8, ''J''&nbsp;=&nbsp;{{sfrac|15|2}} to ''J''&nbsp;=&nbsp;{{sfrac|17|2}} and ''J''&nbsp;=&nbsp;{{sfrac|17|2}} to ''J''&nbsp;=&nbsp;{{sfrac|19|2}}; ''N''&nbsp;=&nbsp;7 to ''N''&nbsp;=&nbsp;8, ''J''&nbsp;=&nbsp;{{sfrac|15|2}} to ''J''&nbsp;=&nbsp;{{sfrac|17|2}} and ''J''&nbsp;=&nbsp;{{sfrac|13|2}} to ''J''&nbsp;=&nbsp;{{sfrac|15|2}}.<ref>{{Cite journal |last1=Klisch |first1=E. |last2=Klaus |first2=Th. |last3=Belov |first3=S. P. |last4=Winnewisser |first4=G. |last5=Herbst |first5=E. |date=1995 |title=Laboratory rotational spectrum of CN in the 1&nbsp;THz region |journal=Astronomy and Astrophysics |volume=304 |pages=L5–L8 |bibcode=1995A&A...304L...5K |bibcode-access=free}}</ref>

==References==
{{reflist}}

{{Molecules detected in outer space}}
{{DEFAULTSORT:Cyano Radical}}
[[Category:Free radicals]]
[[Category:Cyanides]]

{{Sourceattribution|Cyano radical}}