Which of the following isomer has the highest melting point:

Options

A. 1, 2-dichlorobenzene
B. 1, 3-dichlorobenzene
C. 1, 4-dichlorobenzene
D. all isomers have same melting points

Answer

C

Explanation

1, 4-dichlorobenzene (para isomers are more symmetric than ortho and meta).
Explanation : The melting point is based on the strength of the lattice structure of a compound. Para-isomer have a higher melting point in comparison to ortho-isomer and meta-isomer of the same compound. It is because para-isomers are symmetric and have compact crystal lattice in comparison to ortho-isomer and meta-isomer.