Carbon–nitrogen bond explained

A carbon–nitrogen bond is a covalent bond between carbon and nitrogen and is one of the most abundant bonds in organic chemistry and biochemistry.^[1]

Nitrogen has five valence electrons and in simple amines it is trivalent, with the two remaining electrons forming a lone pair. Through that pair, nitrogen can form an additional bond to hydrogen making it tetravalent and with a positive charge in ammonium salts. Many nitrogen compounds can thus be potentially basic but its degree depends on the configuration: the nitrogen atom in amides is not basic due to delocalization of the lone pair into a double bond and in pyrrole the lone pair is part of an aromatic sextet.

Similar to carbon–carbon bonds, these bonds can form stable double bonds, as in imines; and triple bonds, such as nitriles. Bond lengths range from 147.9 pm for simple amines to 147.5 pm for C-N= compounds such as nitromethane to 135.2 pm for partial double bonds in pyridine to 115.8 pm for triple bonds as in nitriles.^[2]

A CN bond is strongly polarized towards nitrogen (the electronegativities of C and N are 2.55 and 3.04, respectively) and subsequently molecular dipole moments can be high: cyanamide 4.27 D, diazomethane 1.5 D, methyl azide 2.17, pyridine 2.19. For this reason many compounds containing CN bonds are water-soluble. N-philes are group of radical molecules which are specifically attracted to the C=N bonds.^[3]

Carbon-nitrogen bond can be analyzed by X-ray photoelectron spectroscopy (XPS). Depending on the bonding states the peak positions differ in N1s XPS spectra.^{[4] [5] [6]}

Nitrogen functional groups

Chemical class	Bond order	Formula	Structural Formula	Example	Avg. C–N bond length (Å)^[7]
Amines	1	R3C-NH2		Methylamine	1.469 (neutral amine) 1.499 (ammonium salt)
Aziridines	1	CH2NHCH2		Mitomycin	1.472
Azides	1	R2C-N3		Phenyl azide	1.38–1.48^[8] 1.47 (methyl azide)^[9] 1.432 (phenyl azide)^[10]
Anilines	1	Ph-NH2		Anisidine	1.355 (sp^2 N) 1.395 (sp^3 N) 1.465 (ammonium salt)
Pyrroles	1			Porphyrin	1.372
Amides	1.2	R-CO-NR2		Acetamide	1.325 (primary) 1.334 (secondary) 1.346 (tertiary)
Pyridines	1.5	pyr		Nicotinamide	1.337
Imines	2	R2C=NR		DBN	1.279 (C=N bond) 1.465 (C–N bond)
Nitriles	3	R-CN		Benzonitrile	1.136
Isonitriles	3	R-NC		TOSMIC	1.154^[11]

See also

• Cyanide
• Other carbon bonds with group 15 elements: carbon–nitrogen bonds, carbon–phosphorus bonds
• Other carbon bonds with period 2 elements: carbon–lithium bonds, carbon–beryllium bonds, carbon–boron bonds, carbon–carbon bonds, carbon–nitrogen bonds, carbon–oxygen bonds, carbon–fluorine bonds
• Carbon–hydrogen bond

Notes and References

1. Organic Chemistry John McMurry 2nd Ed.
2. [CRC Handbook of Chemistry and Physics]
3. 2338–9 . 10.1039/B207729A . 5-Azahexenoyl radicals cyclize via nucleophilic addition to the acyl carbon rather than 5-exo homolytic addition at the imine . 2002 . Falzon . Chantal T. . Ryu . Ilhyong . Schiesser . Carl H. . Chemical Communications . 20 . 12430429.
4. Kato . Tomofumi . Yamada . Yasuhiro . Nishikawa . Yasushi . Otomo . Toshiya . Sato . Hayato . Sato . Satoshi . 2021-07-12 . Origins of peaks of graphitic and pyrrolic nitrogen in N1s X-ray photoelectron spectra of carbon materials: quaternary nitrogen, tertiary amine, or secondary amine? . Journal of Materials Science . 56 . 28 . 15798–15811 . en . 10.1007/s10853-021-06283-5 . 235793266 . 1573-4803. free .
5. 2014-04-01 . Nitrogen-containing graphene analyzed by X-ray photoelectron spectroscopy . Carbon . en . 70 . 59–74 . 10.1016/j.carbon.2013.12.061 . 0008-6223. Yamada . Yasuhiro . Kim . Jungpil . Matsuo . Shintaro . Sato . Satoshi .
6. 2021-09-01 . Unveiling Bonding States and Roles of Edges in Nitrogen-Doped Graphene Nanoribbon by X-ray Photoelectron Spectroscopy . Carbon . en . 10.1016/j.carbon.2021.08.085 . 0008-6223. Yamada . Yasuhiro . Tanaka . Haruki . Kubo . Shingo . Sato . Satoshi . 185 . 342–367 . 239687362 .
7. F. H. Allen, O. Kennard, D. G. Watson, L. Brammer, A. G. Orpen. Tables of bond Lengths determined by X-Ray and Neutron Diffraction. Part 1. Bond Lengths in Organic Compounds. J. Chem. Soc. Perkin Trans. II 1987, S1-S19.
8. Azidoacetamide, a neutral small organic azide . M. . Kumasaki . K. . Kinbara . Y. . Wada . M. . Arai . M. . Tamura . . 2001 . 57 . o6–o8 . 10.1107/S160053680001850X.
9. An Electron Diffraction Investigation of the Molecular Structure of Methyl Azide . R. L. . Livingston . C. N. Ramachandra . Rao . C. N. R. Rao . . 1960 . 64 . 6 . 756–759 . 10.1021/j100835a012.
10. . 2009 . 11 . 3056–3058 . Controllable Selective Functionalization of a Cavitand via Solid State Photolysis of an Encapsulated Phenyl Azide . Gerald . Wagner . Vladimir B. . Arion . Lothar . Brecker . Carsten . Krantz . Jean-Luc . Mieusset . Udo H. . Brinker . 14 . 10.1021/ol901122h. 19537769 .
11. . 71 . 2015 . o412 . Crystal structure of p-toluenesulfonylmethyl isocyanide . Huma . Bano . Sammer . Yousuf . 6 . 10.1107/S2056989015008816. 26090196 . 4459310 . 26154257 . free .