||Chapter 2 :
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.
- 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
(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, HC≡CH
- both C are sp hybridised
- 2 C-H σ bonds are made by the interaction
of C sp with H1s orbitals (see red
- 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)
Now is a good time to try a few questions about
bonding and hybridisation.
- sp occurs when a C has 2 attached groups
- sp has 50% s and 50% p character
- the 2 sp hybrids point in opposite directions
at 180o to each other
- each sphybrid is involved in a σ bond
- the remaining p orbitals forms the 2π bonds
- view a triple bond as a σ + 2π bonds