Question

In benzene all $C - C$ bond length between all carbon atoms are equal because of:
A.Tautomerism
B.$S{p^2}$ hybridisation
C.Isomerism
D.Resonance

Answer 1

Benzene is an organic molecule. It is a resonance hybrid of various canonical structures. Resonance is the delocalization of electrons. Electron delocalization can stabilize benzene.
Complete step by step answer:
Benzene is an organic molecule having the molecular formula ${C_6}{H_6}$ . The structure of benzene is given below.

All the carbon atoms are $S{p^2}$ hybridised. These $S{p^2}$ hybrid orbitals are arranged in a triangular planar fashion. One of the unhybridized p orbital will remain perpendicular to the above plane. Each C atom will use two of the $S{p^2}$ hybridized orbital and form 2 $C - C$ sigma bonds by $s{p^2} - s{p^2}$ head-on overlap. The remaining $S{p^2}$ orbital is used to form a sigma bond by overlap with the 1s orbital of hydrogen. There will be 6 $C - C$ sigma bonds that form the sides of the hexagon. All the $C - C - C$ bond angles will be $120^\circ$ .
According to the resonance concept, benzene is a resonance hybrid of the following structures.

The resonance explains the unusual stability of benzene. The resonance hybrid will have a lower energy than the contributing structures. The resonance energy of benzene is -150.5 kJ/mol.
The six mutually parallel unhybridized p orbitals will stand perpendicular to the hexagonal carbon ring and overlap sideways above and below the plane of the ring. Due to the delocalization of pi electrons all the carbon-carbon bonds of benzene have the same length.

Note: All the six carbon-carbon bonds in benzene have equal length. It is greater than carbon-carbon double bond length and lower than carbon-carbon single bond length. Carbon-carbon bond length in benzene is 1.39 angstrom. In contrast to alkenes benzene undergo substitution reactions rather than additional reactions. There are two resonance structures for benzene; these are kekule and dewar structures. Kekule structure has some limitations. It could not explain the remarkable stability of benzene towards strong oxidants like $KMn{O_4}$ .