Distinction between σ -Bond and π-Bond

Distinction between σ -bond and π-bond

σ – bond

1. A σ-bond is formed by the co-axial overlapping (head to head overlap) of atomic orbital.
2. A σ –bond may be formed by hybrid orbitals or by atomic orbital. Examples: s-sp³ or s-s or p-p orbital.
3. A sigma (σ –bond) is stronger and is less reactive. Example: Energy of C-C sigma bond is 83 Kcal/Mole.
4. A sigma bond under goes free rotation. So geometrical isomerism isn’t seen in saturated compounds.
5. A single bonds are σ –bond. These are independent bonds.

π -bond

1. A π-bond is formed by the sideway or lateral overlapping of orbital
2. A π -bond not be formed by hybrid orbital; unhybridyzed orbitals can only form π-bond.
3. A π -bond is weaker and is more reactive. Example: Energy of C-C, π -bond is 63 Kcal/mole.
4. Rotation of π –bond is hindered and it gives rise to geometrical isomerism.
5. π –bond can not exist without σ –bond. There are not independent bonds. Except s-orbital and hybrid orbitals, it can occur in all other orbitals.