Triple bond

A triple bond in chemistry is a chemical bond between two atoms involving six bonding electrons instead of the usual two in a covalent single bond. The most common triple bond, that between two carbon atoms, can be found in alkynes. Other functional groups containing a triple bond are cyanides and isocyanides. Some diatomic molecules, such as dinitrogen and carbon monoxide are also triple bonded. In skeletal formula the triple bond is drawn as three parallel lines (≡) between the two connected atoms.^[1][2][3]

Triple bonds are stronger than single bonds or double bonds and they are also shorter. The bond order is three.

acetylene, H−C≡C−H	cyanogen, N≡C−C≡N	carbon monoxide, C≡O
Chemical compounds with triple bonds

Bonding

The types of bonding can be explained through in terms of orbital hybridization. In the case of acetylene each carbon atom has two sp orbitals and two p-orbitals. The two sp orbitals are linear with 180° angles and occupy the x-axis (cartesian coordinate system). The p-orbitals are perpendicular on the y-axis and the z-axis. When the carbon atoms approach each other the sp orbitals overlap to form a sp-sp sigma bond. At the same time the p_z-orbitals approach and together they form a p_z-p_z pi-bond. Likewise, the other pair of p_y-orbitals form a p_y-p_y pi-bond. The result is formation of one sigma bond and two pi bonds.

In the bent bond model the triple bond can also formed by the overlapping of three sp³ lobes without the need to invoke a pi-bond.^[4]

References

1. March, Jerry (1985), Advanced Organic Chemistry: Reactions, Mechanisms, and Structure (3rd ed.), New York: Wiley, ISBN 0-471-85472-7
2. Organic Chemistry 2nd Ed. John McMurry
3. Pyykkö, Pekka; Riedel, Sebastian; Patzschke, Michael (2005). "Triple-Bond Covalent Radii". Chemistry - A European Journal 11 (12): 3511–20. doi:10.1002/chem.200401299. PMID 15832398.
4. Advanced Organic Chemistry Carey, Francis A., Sundberg, Richard J. 5th ed. 2007