Among the three isomeric dichlorobenzenes , which has the highest boiling point and highest melting point ?

Explanation

Boiling point of o-dichlorobenzene is greater than the boiling point of m -and p-dichlorobenzenes due to its greater polar nature. Boiling point order is : `o - gt m - gt p -` dichlorobenzene. Melting points of p- dichlorobenzene is greater than that of o- and m-dichlorobenzenes. It is due to symmetry of para-isomer of dichlorobenzene that fits in crystal lattice better as compared to o- and m-isomers. Melting points decrease in the order : `p- gt o- gt m-` dichlorobenzene