Question

. What is resonance? Discuss the resonance in benzene?​

Answer 1

Resonance is a method of describing the delocalized electrons in some molecules where the bonding cannot be explicitly expressed by a single Lewis structure.

The oscillating double bonds in the benzene ring are explained with the help of resonance structures as per valence bond theory. All the carbon atoms in the benzene ring are sp2 hybridized. One of the two sp2 hybridized orbitals of one atom overlaps with the sp2 orbital of adjacent carbon atom forming six C-C sigma bonds. Other left sp2 hybridized orbitals combine with s orbital of hydrogen to form six C-H sigma bonds. Remaining unhybridized p orbitals of carbon atoms form π bonds with adjacent carbon atoms by lateral overlap.

This explains an equal possibility for the formation of C1 –C2, C3 – C4, C5 – C6 π bonds or C2 – C3, C4 – C5, C6-C1 π bonds. The hybrid structure is represented by inserting a circle in the ring as shown below in the figure. Hence, it explains the formation of two resonance structures proposed by Kekule.

Benzene - Kekule structure

Answer 2

Resonance is a method of describing the delocalized electrons in some molecules where the bonding cannot be explicitly expressed by a single Lewis structure.