Which compound has highest melting point ?

Options

A. o-Dibromobenzene
B. m-Dibromobenzene
C. p-Dibromobenzene
D. Dibromobenzene

Explanation

To determine which compound has the highest melting point among ortho-dibromobenzene, meta-dibromobenzene, and para-dibromobenzene, we can follow these steps:

### Step 1: Understand the Structures
- **Ortho-dibromobenzene** has two bromine atoms attached to adjacent carbon atoms on the benzene ring.
- **Meta-dibromobenzene** has two bromine atoms attached to carbon atoms that are separated by one carbon atom on the benzene ring.
- **Para-dibromobenzene** has two bromine atoms attached to carbon atoms that are opposite each other on the benzene ring.

### Step 2: Analyze Symmetry
- The melting point of a compound is influenced by its molecular symmetry. Generally, compounds with higher symmetry tend to pack better in the solid state, leading to higher melting points.
- **Ortho-dibromobenzene** has low symmetry due to the adjacent bromine atoms.
- **Meta-dibromobenzene** has moderate symmetry, but it is still less symmetrical than para-dibromobenzene.
- **Para-dibromobenzene** exhibits the highest symmetry because the bromine atoms are positioned directly opposite each other.

### Step 3: Conclusion
- Since para-dibromobenzene has the highest symmetry, it will have the highest melting point among the three compounds.

Therefore, the compound with the highest melting point is **para-dibromobenzene**.