expert its urgent i m unable to think u have to give the best explaation with the help of diag must reqd

However, the melting point of para-isomer is higher than those of ortho- and meta- isomers due to better symmetry in the structure.the higher melting point of para isomer is due to its symmetry which leads to more close packing of its molecule

in a crystal lattice and consequently strong intermolecular forces

2- how to decide which pdt is major which is minor in any rxn give also examples

1) Actually in case of Para isomers molecules are more ordered and symmetrically packed as compared to that in ortho and meta isomers.Thus when we compare melting points of these thre isomers we should know there Entropy change as well as enthalpy of fusion.
These three isomers will have comparable enthalpy of fusion that is almost same for all three of them. But entropy change will be maximum for the parta isomers since they were the most ordered arrangement of molecules because of interactions and more energy would be required to break them.
Thus the melting point will be highest for the para isomers.
Another reason is that since para isomer is more symetrical that is two electronegative atoms are farthest and cancels out the dipole moment making the molecule non polar.
While in case of ortho and para the electronegative atoms on the ring are closer and have certain dipole moments which makes them polar in nature.
Following values explains the difference in entropy change for all three of them :



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