An aromatic compound has molecular formula `C_7 H_7 Br`. Give the possible isomers and the appropriate method to distinguish them.

Options

A. 3 isomers, by heating with `AgNO_3` solution
B. 4 isomers, by treating with `AgNO_3` solution
C. 4 isomers, by oxidation
D. 5 isomers, by oxidation

Answer

To solve the problem of identifying the possible isomers of the aromatic compound with the molecular formula C7H7Br and methods to distinguish them, we can follow these steps:

### Step 1: Identify the Structure
The molecular formula C7H7Br indicates that we have an aromatic compound, which suggests the presence of a benzene ring. The formula can be represented as C6H5R, where R is a substituent. Here, R can be either a methyl group (–CH3) or a bromine atom (–Br).

### Step 2: Determine Possible Isomers
1. **Bromotoluene Isomers**:
- **Ortho-bromotoluene**: The bromine atom is on the adjacent carbon to the methyl group.
- **Meta-bromotoluene**: The bromine atom is on the carbon that is one carbon away from the methyl group.
- **Para-bromotoluene**: The bromine atom is directly opposite the methyl group on the benzene ring.

2. **Bromomethylbenzene**:
- **Benzyl bromide**: Here, the bromine is attached to a –CH2– group, which is directly connected to the benzene ring.

### Summary of Possible Isomers:
1. Ortho-bromotoluene (1-bromo-2-methylbenzene)
2. Meta-bromotoluene (1-bromo-3-methylbenzene)
3. Para-bromotoluene (1-bromo-4-methylbenzene)
4. Benzyl bromide (benzyl bromide)

### Step 3: Distinguishing the Isomers
To distinguish between these isomers, we can use the oxidation method.

- **Oxidation of Methyl Group**:
- The methyl group (–CH3) in ortho, meta, and para-bromotoluene can be oxidized to form a carboxylic acid (–COOH).
- Benzyl bromide can also be oxidized to form benzoic acid.

### Conclusion
All four isomers can be distinguished by their reactivity towards oxidation. The presence of the carboxylic acid group formed from the oxidation will confirm the structure of the original compound.