Question

Which of the set of isomers of C₆H₄Cl₂ is having equal dipole moment with C₆H₅Cl and C₆H₆ respectively

(A) ortho and meta          

(B) meta and para 

(C) ortho and para 

(D) para and ortho

Answer 1

Correct Answer : B. meta and para 

The expression for dipole moment is

In case of meta dichloro benzene, the bond angle between two carbon chlorine bonds is 120^o

Hence, cosθ=cos120=−0.5 and μ₁ =μ₂ =μ_R
Hence, the dipole moment of meta dichlorobenzene is equal to that of chlorobenzene.
In case of para dichlorobenzene, the bond angle between two carbon chlorine bonds is 180^o.
 Hence, cosθ=cos180=−1 and μ_R =0.
Hence, the dipole moment of para dichlorobenzene is equal to that of benzene.