Chlorination of benzene in the presence of anhydrous AlCl ₃ yields a mixture of disubstituted isomers X and Y. Isomer Y has a significantly higher melting point than X and is easily separated by crystallization. Identify isomer Y and the primary reason for its higher melting point.

Step-by-step solution

Chlorination of benzene in the presence of a Lewis acid yields a mixture of o -dichlorobenzene and p -dichlorobenzene as the major disubstituted products. The para-isomer ( p -dichlorobenzene) has a significantly higher melting point than the ortho-isomer. This is because the p -isomer is highly symmetrical, which allows its molecules to pack more closely and efficiently in the crystal lattice. As a result of this close packing, stronger intermolecular forces exist in the crystal lattice of the para-isomer, requiri