question_answer

  p-dichloro benzene has higher melting point and lower solubility than those of o-and m-isomers. Discuss.                                                [2]

Answer:

  Melting point of para-dichloro benzene is higher than of ortho and mete-isomers. It is due to symmetry of para-isomers that fits in crystal lattice better as compared to ortho and meta-isomers. p-dichlorobenzene has zero dipole moment and thus is non-polar. Hence, it is less soluble in water as compared to ortho and mera-isomers.                                                           [1] Dipole moment of o > m >p Also due to symmetry of para-isomers, force of attraction is very high among molecules hence to make soluble high energy is required. Thus solubility of para-isomers is very low.                                                         [1]