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.

Nitrogen functional groups

Chemical class Bond order Formula Structural Formula Example Avg. C–N bond length (Å)3
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

CH He
CLi CBe CB CC CN CO CF Ne
CNa CMg CAl CSi CP CS CCl CAr
CK CCa CSc CTi CV CCr CMn CFe CCo CNi CCu CZn CGa CGe CAs CSe CBr CKr
CRb CSr CY CZr CNb CMo CTc CRu CRh CPd CAg CCd CIn CSn CSb CTe CI CXe
CCs CBa CHf CTa CW CRe COs CIr CPt CAu CHg CTl CPb CBi CPo CAt Rn
Fr CRa Rf Db Sg Bh Hs Mt Ds Rg Cn Uut Fl Uup Lv Uus Uuo
CLa CCe CPr CNd CPm CSm CEu CGd CTb CDy CHo CEr CTm CYb CLu
Ac CTh CPa CU CNp CPu CAm CCm CBk CCf CEs Fm Md No Lr
Chemical bonds to carbon
Core organic chemistry Many uses in chemistry
Academic research, but no widespread use Bond unknown

References

  1. ^ Organic Chemistry John McMurry 2nd Ed.
  2. ^ CRC Handbook of Chemistry and Physics 65Th Ed.
  3. ^ 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.