It is a coupling reaction of diazonium salt.In it the aromatic ring undergoing attack by diazoniumion must contain a powerful electron releasing group,generally –OH, –NR₂, –NHR or –NH₂. Substitution usually secures para-to the activating group.It has been established experimentally that coupling is electrophilic aromatic substitutions.

Among the three given hybrid orbitals, sp hybrid orbital is most electronegative. Contribution of sin sp hybrid orbital is maximum so this orbital is closer to nucleus.Naturally it will have greater tendency to pull electron towards it. Hence it becomes more electronegative and sp³ becomes least electronegative.

Styrene can be purified by vacuum distillation.

Due to + I-effect of the CH₃ group, toluene has much higher electron density in the ring than benzene,nitro benzene and benzoic acid as they show– I-effect and hence is most reactive towards nitration.

Benzoic acid, camphor and naphthalene sublime on heating hence, they are purified by sublimation method.