Question

Why para chloro benzene has high melting point than ortho and meta measurements?

Answer 1

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Generally, the melting point of para isomer is quite higher than that of ortho or meta isomers.

This is due to the fact that it has a symmetrical structure and therefore, its molecules can easily pack closely in the crystal lattice.

As a result, intermolecular forces of attraction are stronger and therefore, greater energy is required to break its lattice and its melts at higher temperature. .

If you consider solubility. These are insoluble in water but soluble in organic solvents.

Generally, para isomers are highly soluble in organic solvents than ortho.

Every compound (more specifically solids) does not dissolve in a given compound.
In general, a liquid dissolves in a liquid if the intermolecular interactions are similar. This is in accordance with the rule "like dissolves like", ionic or polar compounds dissolve more readily in polar solvents.

Non-polar compounds (covalent or organic) are soluble in non-polar solvents.

If you consider p-dichlorobenzene, it has zero dipole moment and thus is more non-polar than o-dichlorobenzene which has dipole moment of about 2.54 D.
So, non-polar p-dichlorobenzene dissolves more readily than o-dichlorobenzene in non-polar (organic) solvents.

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