Ch 2: sp hybridisation

Chapter 2 : Alkanes

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.

Blend" (i.e. hybridise) the s and a p orbital...

since we "mixed" 2 orbitals, we get a set of 2 sporbitals
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, HC≡CH

both C are sp hybridised
2 C-H σ bonds are made by the interaction of C spwith H1s orbitals (see red arrows)
1 C-C σ bond is made by the interaction of C spwith another C sporbital (see green arrow)
2 C-C π bonds are made by the interaction of the 2 pairs of C p orbitals (see black arrows)

Summary

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 180^o 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

Now is a good time to try a few questions about bonding and hybridisation.