Everipedia Logo
Everipedia is now IQ.wiki - Join the IQ Brainlist and our Discord for early access to editing on the new platform and to participate in the beta testing.
Carbon–hydrogen bond

Carbon–hydrogen bond

The carbon-hydrogen bond (C–H bond) is a bond between carbon and hydrogen atoms that can be found in many organic compounds.[1] This bond is a covalent bond meaning that carbon shares its outer valence electrons with up to four hydrogens. This completes both of their outer shells making them stable.[2] 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 (2.55) and H (2.2)—the electronegativity difference between these two atoms is 0.35. Because of this small difference in electronegativities, the C−H bond is 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 hydrocarbons. Collectively they are known as hydrocarbons.

In October 2016, astronomers reported that the very basic chemical ingredients of life—the carbon-hydrogen molecule (CH, or methylidyne radical), the carbon-hydrogen positive ion (CH+) and the carbon ion (C+)—are the result, in large part, of ultraviolet light from stars, rather than in other ways, such as the result of turbulent events related to supernovae and young stars, as thought earlier.[3]

Reactions

The C−H bond in general is very strong, so it is relatively 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. Many enzymes are known, however, to affect these reactions.[4]

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.[5][6]

BondHydrocarbon radicalMolar Bond Dissociation Energy (kcal)Molar Bond Dissociation Energy (kJ)
CH3−HMethyl104440
C2H5−HEthyl98410
(CH3)2HC−HIsopropyl95400
(CH3)3C−Htert-Butyl93390
CH2=CH−Hvinyl112470
HC≡C−Hethynyl133560
C6H5−Hphenyl110460
CH2=CHCH2−HAllyl88370
C6H5CH2−HBenzyl85360
OC4H7−Htetrahydrofuranyl92380
CH3C(O)CH2−Hacetonyl96400

References

[1]
Citation Linkopenlibrary.orgMarch, Jerry (1985), Advanced Organic Chemistry: Reactions, Mechanisms, and Structure (3rd ed.), New York: Wiley, ISBN 0-471-85472-7
Sep 26, 2019, 12:41 AM
[2]
Citation Linkcyberbridge.mcb.harvard.edu"Life Sciences Cyberbridge". Covalent Bonds. Archived from the original on 2015-09-18. Retrieved 2015-09-15.
Sep 26, 2019, 12:41 AM
[3]
Citation Linkwww.jpl.nasa.govLandau, Elizabeth (12 October 2016). "Building Blocks of Life's Building Blocks Come From Starlight". NASA. Retrieved 13 October 2016.
Sep 26, 2019, 12:41 AM
[4]
Citation Linkdoi.orgBollinger, J. M. Jr., Broderick, J. B. "Frontiers in enzymatic C-H-bond activation" Current Opinion in Chemical Biology 2009, vol. 13, page 51-7. doi:10.1016/j.cbpa.2009.03.018
Sep 26, 2019, 12:41 AM
[5]
Citation Linkwww.cem.msu.edu"Bond Energies". Organic Chemistry, Michigan State University. Archived from the original on 29 August 2016.
Sep 26, 2019, 12:41 AM
[6]
Citation Linkopenlibrary.orgYu-Ran Luo and Jin-Pei Cheng "Bond Dissociation Energies" in CRC Handbook of Chemistry and Physics, 96th Edition
Sep 26, 2019, 12:41 AM
[7]
Citation Linkweb.archive.org"Life Sciences Cyberbridge"
Sep 26, 2019, 12:41 AM
[8]
Citation Linkcyberbridge.mcb.harvard.eduthe original
Sep 26, 2019, 12:41 AM
[9]
Citation Linkwww.jpl.nasa.gov"Building Blocks of Life's Building Blocks Come From Starlight"
Sep 26, 2019, 12:41 AM
[10]
Citation Linkdoi.org10.1016/j.cbpa.2009.03.018
Sep 26, 2019, 12:41 AM
[11]
Citation Linkweb.archive.org"Bond Energies"
Sep 26, 2019, 12:41 AM
[12]
Citation Linkwww.cem.msu.eduthe original
Sep 26, 2019, 12:41 AM
[13]
Citation Linken.wikipedia.orgThe original version of this page is from Wikipedia, you can edit the page right here on Everipedia.Text is available under the Creative Commons Attribution-ShareAlike License.Additional terms may apply.See everipedia.org/everipedia-termsfor further details.Images/media credited individually (click the icon for details).
Sep 26, 2019, 12:41 AM