Carbon–hydrogen bond

The C-H bond is a bond between carbon and hydrogen atoms, most commonly found in organic compounds. Carbon-hydrogen bonds have a bond length of about 1.09 Å (1.09 × 10^-10 m) and a bond energy of about 413 kJ/mol (see table below). Using Pauling's scale--C (2.5) and H (2.1)--the electronegativity difference between these two atoms is 0.4. Because of this small difference in electronegativities, the C-H bond generally regarded as being non-polar. In structural formulas of molecules, the hydrogen atoms are often omitted. Compound classes consisting solely of C-H bonds and C-C bonds are alkanes, alkenes, alkynes, and aromatic compounds.

Reactions

The C-H bond in general is unreactive. In several compound classes, collectively called carbon acids, the C-H bond can be sufficiently acidic for proton removal. Unactivated C-H bonds are found in alkanes and are not adjacent to a heteroatom]] (O, N, Si, etc). Such bonds usually only participate in radical substitution. Another reaction type involving C-H bonds is so-called C-H bond activation mediated by metals and carbene C-H insertion.

Although the C-H bond is one of the strongest, it varies over 30% in magnitude for fairly stable organic compounds, even in the absence of heteroatoms.

Bond	Hydrocarbon radical	Bond Dissociation Energy (kcal/mole)
CH3-H	Methyl	103
C2H5-H	Ethyl	98
(CH3)2HC-H	Isopropyl	95
(CH3)3C-H	tert-Butyl	93
CH2=CH-H	vinyl	112
C6H5-H	phenyl	110
CH2=CHCH2-H	Allyl	88
C6H5CH2-H	Benzyl	85
OC4H7-H	tetrahydrofuranyl	92

Nomenclature

The C-H bond is formally named carbogen.

See also

• Hydrocarbon