JEE Main levelSingle correct optionDifficulty 2 of 3hx099
The melting points of the dichlorobenzenes are about 256 K for the ortho, 249 K for the meta and 326 K for the para isomer. The reason for the much higher value for the para isomer is that
Ait forms hydrogen bonds between molecules
Bit has the largest molar mass of the three
Cits symmetrical shape packs more efficiently in the crystal lattice
Dit has the largest dipole moment of the three
Answer: C
All three isomers have the same molar mass and none can hydrogen-bond. The para isomer is highly symmetrical (dipole moment zero) and fits into the crystal lattice better, which raises the lattice energy and the melting point.