Question

Arrange the following compounds in order of increasing dipole moment.

• A. $I<IV<II<III$
• B. $IV<I<II<III$
• C. $IV<I<III<II$
• D. $IV<II<I<III$

Answer 1

The correct option is B $IV<I<II<III$

Dipole moment of $p-$ dichlorobenzene is zero because of symmetrical structure. $o-$ and $m-$ dichlorobenzene have higher dipole moments than toluene due to high electronegativity of chlorine than $-C{H}_3$ group. Further, the $o-$dichlorobenzene has higher dipole moment due to lower bond angle than the $m-$isomer. Hence, the order of increasing dipole moment is :
$IV<I<II<III$