Triple bond
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Atriple bondinchemistryis achemical bondbetween twoatomsinvolving sixbonding electronsinstead of the usual two in acovalent single bond.Triple bonds are stronger than the equivalentsingle bondsordouble bonds,with abond orderof three. The most common triple bond is in anitrogenN2molecule; the second most common is that between twocarbonatoms, which can be found inalkynes.Otherfunctional groupscontaining a triple bond arecyanidesandisocyanides.Some diatomic molecules, such asdiphosphorus[1]andcarbon monoxide,are also triple bonded. Inskeletal formulaethe triple bond is drawn as three parallel lines (≡) between the two connected atoms.[2][3][4]
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acetylene,H−C≡C−H | cyanogen,N≡C−C≡N | carbon monoxide,C≡O |
Bonding
[edit]Triple bonding can be explained in terms oforbital hybridization.In the case of acetylene, each carbon atom has twosp-orbitalsand twop-orbitals.The two sp-orbitals are linear, with 180°bond angles,and occupy the x-axis in thecartesian coordinate system.The p-orbitals areperpendicularto the sp-orbitals on the y-axis and the z-axis. When the atoms approach each other, the sp orbitals overlap to form an sp-spsigma bond.At the same time the pz-orbitals approach and together they form a pz-pzpi-bond.Likewise, the other pair of py-orbitals form a py-pypi-bond. The result is formation of one sigma bond and two pi bonds.
In thebent bond model,the triple bond can also formed by the overlapping of three sp3lobes without the need to invoke a pi-bond.[5]
Triple bonds between elements heavier than oxygen
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Many elements beyond oxygen can form triple bonds. These bonds are common in some transition metals.Hexa(tert-butoxy)ditungsten(III)andHexa(tert-butoxy)dimolybdenum(III)are well known examples, in which the metal-metal bond distance is about 233 pm.[6]Hexa(tert-butoxy)ditungsten(III)has attracted particular attention for its reactions with alkynes, leading to metal-carbon triple bonded compounds of the formula RC≡W(OBut)3[7]
Additionally,phosphoruscan exist as the highly reactive diatomic moleculediphosphorus,which has roughly half thebond-dissociation energyof dinitrogen.[1]
References
[edit]- ^abHuber, K. P.; Herzberg, G. (1979).Molecular Spectra and Molecular Structure IV. Constants of Diatomic Molecules.New York: Van Nostrand.ISBN978-0442233945.
- ^March, Jerry(1985),Advanced Organic Chemistry: Reactions, Mechanisms, and Structure, 3rd edition,New York: Wiley,ISBN9780471854722,OCLC642506595
- ^Organic Chemistry2nd Ed. John McMurry
- ^Pyykkö, Pekka; Riedel, Sebastian; Patzschke, Michael (2005). "Triple-Bond Covalent Radii".Chemistry: A European Journal.11(12): 3511–20.doi:10.1002/chem.200401299.PMID15832398.
- ^Advanced Organic ChemistryCarey, Francis A., Sundberg, Richard J. 5th ed. 2007
- ^Chisholm, Malcolm H.; Gallucci, Judith C.; Hollandsworth, Carl B. (2006). "Crystal and molecular structure of W2(OBut)6and electronic structure calculations on various conformers of W2(OMe)6".Polyhedron.25(4): 827–833.doi:10.1016/j.poly.2005.07.010.
- ^.Listemann, Mark L.; Schrock, Richard R. (1985). "Multiple metal carbon Bonds. 35. A General Route to tri-tert-Butoxytungsten Alkylidyne complexes. Scission of Acetylenes by Ditungsten Hexa-tert-butoxide ".Organometallics.4:74–83.doi:10.1021/om00120a014.