Return to Contents Chapter 2 : Alkanes  Ch 2 contents
sp hybridisation

When a C atom is attached to 2 groups and so is involved in 2 π bonds, it requires 2 orbitals in the hybrid set. This requires that it is sp hybridised. The general "steps" are similar to that for seen previously sp3 and sp2 hybridisation.

sp hybridisation
  • Blend" (i.e. hybridise) the s and a p orbital...
    • since we "mixed" 2 orbitals, we get a set of 2 sp orbitals
    • the other two p orbital remain unaffected
    • both sp hybrids and the 2 p orbitals contain a single unpaired electron
creating the hybrids from an s and a p orbital

(note the sp hybrids are offset horizontally to allow both lobes to be seen)

You can view an animation of the hybridisation of the C orbitals if you wish.

  • In ethyne, HCCH
    • both C are sp hybridised
    • 2 C-H σ bonds are made by the interaction of C sp with H1s orbitals (see red arrows)
    • 1 C-C σ bond is made by the interaction of C sp with another C sp orbital (see green arrow)
    • 2 C-C π bonds are made by the interaction of the 2 pairs of C p orbitals (see black arrows)
orbitals to bonds for ethyne
Summary Now is a good time to try a few questions about bonding and hybridisation.

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organic chemistry © Dr. Ian Hunt, Department of Chemistry University of Calgary