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. Triple bonds are stronger than the equivalent single bonds or double bonds, with a bond order of three. 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 formulae the triple bond is drawn as three parallel lines (≡) between the two connected atoms.
|acetylene, H−C≡C−H||cyanogen, N≡C−C≡N||carbon monoxide, C≡O|
|Chemical compounds with triple bond|
The types of bonding can be explained 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 an sp-sp sigma bond. At the same time the pz-orbitals approach and together they form a pz-pz pi-bond. Likewise, the other pair of py-orbitals form a py-py pi-bond. The result is formation of one sigma bond and two pi bonds.
Triple bonds between elements heavier than carbon
Triple bonds are found for many elements beyond carbon. They are common for transition metals. Hexa(tert-butoxy)ditungsten(III) and Hexa(tert-butoxy)dimolybdenum(III) are well known examples. The M-M distance is about 233 pm. The W2 compound has attracted particular attention for its reactions with alkynes, leading to metal-carbon triple bonded compounds of the formula RC≡W(OBut)3
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