Arrange in order of increasing dipole movement.
I. Toulene
II. m - dichlorobenzene
III. o - dichlorobenzene
IV. p - dichlorobenzene
CH3 of toluene is e− donating
In p-dichlorobenze, the dipole moments by each Cl cancel out and thus no net dipole moment exists. Among m and o isomers, Ortho isomer has more net dipole moment.
Toulene has a e− donating −CH3 group which is weaker than chlorine
So, the order will be:-
IV < I < II < III