Saturday, October 31, 2009

sp2 hybridization

When a C atom is attached to 3 groups and so is involved in 3 s bonds, it requires 3 orbitals in the hybrid set. This requires that it is sp2 hybridised. The general "steps" are similar to that for seen previously sp3 hybridization.

sp2 hybridization
  • "Blend" (i.e. hybridise) the s and the 2 p orbitals...
    • since we "mixed" 3 orbitals, we get a set of 3 sp2 orbitals
    • the other p orbital remains unaffected
    • each sp2 hybrid and the p orbital contains a single unpaired electron
  • In ethene, H2C=CH2
    • both C are sp2 hybridised.
    • 4 C-H s bonds are made by the interaction of C sp2 with H1s orbitals (see red arrows)
    • 1 C-C s bond is made by the interaction of C sp2 with another C sp2 orbital (see green arrow)
    • 1 C-C p bond is made by the interaction of the C p with the other C p orbital (see black arrows)
orbitals to bonds for ethene

Summary

  • sp2 occurs when a C has 3 attached groups
  • sp2 has 33% s and 67% p character
  • the 3 sp2 hybrids point towards the corners of a triangle at 120o to each other
  • each sp2 hybrid is involved in a s bond
  • the remaining p orbital forms the p bond
  • view a double bond as a s + p bond

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