Carbon–nitrogen bond

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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.

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.[3][4][5]

Nitrogen functional groups[]

Chemical class Bond order Formula Structural Formula Example Avg. C–N bond length (Å)[6]
Amines 1 R2C-NH2 Primary amine methylamine
Methylamine
 1.469 (neutral amine)
1.499 (ammonium salt)
Aziridines 1 CH2NHCH2 Aziridine Phenyl azide
Mitomycin
 1.472
Azides 1 R2C-N3 Azide Phenyl azide
phenyl azide
Anilines 1 Ph-NH2 Aniline Ansidine
Anisidine
 1.355 (sp2 N)
1.395 (sp3 N)
1.465 (ammonium salt)
Pyrroles 1 amide Acetamide
Porphyrin
 1.372
Amides 1.2 R-CO-NR2 amide Acetamide
Acetamide
 1.325 (primary)
1.334 (secondary)
1.346 (tertiary)
Pyridines 1.5 pyr pyridine Nicotinamide
Nicotinamide
 1.337
Imines 2 R2C=NR imine Ansidine
DBN
 1.279 (C=N bond)
1.465 (C–N bond)
Nitriles 3 R-CN Nitrile Benzonitrile
Benzonitrile
 1.136
Isonitriles 3 R-NC isonitrile TOSMIC
TOSMIC

See also[]

References[]

  1. ^ Organic Chemistry John McMurry 2nd Ed.
  2. ^ CRC Handbook of Chemistry and Physics 65Th Ed.
  3. ^ 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. doi:10.1007/s10853-021-06283-5. ISSN 1573-4803.
  4. ^ "Nitrogen-containing graphene analyzed by X-ray photoelectron spectroscopy". Carbon. 70: 59–74. 2014-04-01. doi:10.1016/j.carbon.2013.12.061. ISSN 0008-6223.
  5. ^ "Unveiling Bonding States and Roles of Edges in Nitrogen-Doped Graphene Nanoribbon by X-ray Photoelectron Spectroscopy". Carbon. 2021-09-01. doi:10.1016/j.carbon.2021.08.085. ISSN 0008-6223.
  6. ^ 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.
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