Question

The dipole moment of chlorobenzene is 1.6 D.The expected dipole moment of meta -diclorobenzene is:

• A. 1.6 D
• B. 3.2 D
• C. 1.6 $\sqrt{2}$ D
• D. 0.0D

Answer 1

The correct option is A 1.6 D

In meta dichlorobenzene, two C-Cl bond vectors are present at an angle of 120 degrees.
Hence, the resultant dipole moment will be: $\mu =\sqrt{{\mu }_1^2+{\mu }_2^2+2{\mu }_1{\mu }_{2}cos\theta }=\sqrt{2{\mu }_1^2(1+cos\theta )}={\mu }_1$ $=1.6D$Where, $\theta ={120}^{0}and{\mu }_1={\mu }_2$, $cos120=-0.5$
Hence, option $A$ is correct.