The number of isomers of dibromobiphenyl (Biphenyl- `C_(6)H_(5)`) is:

Options

A. 8
B. 10
C. 12
D. 4

Answer

To determine the number of isomers of dibromobiphenyl (C₁₂H₈Br₂), we need to analyze the biphenyl structure and the positions where the bromine atoms can be attached. Here’s a step-by-step solution:

### Step 1: Understand the Structure of Biphenyl
Biphenyl consists of two phenyl rings (C₆H₅) connected by a single bond. Each phenyl ring has six carbon atoms and five hydrogen atoms.

### Step 2: Identify the Positions for Substitution
In biphenyl, the carbon atoms can be numbered as follows:
- For the first ring (C₁ to C₆)
- For the second ring (C₁' to C₆')

Since the biphenyl structure is symmetrical, we can focus on the positions of the bromine atoms on the rings.

### Step 3: Determine Possible Isomer Configurations
1. **Both Bromines on the Same Ring:**
- **1,1-Dibromobiphenyl**: Both bromines on the same carbon (not possible as each carbon can only have one bromine).
- **1,2-Dibromobiphenyl**: Bromines on adjacent carbons (C₁ and C₂ or C₁' and C₂').
- **1,3-Dibromobiphenyl**: Bromines on carbons with one carbon in between (C₁ and C₃ or C₁' and C₃').
- **1,4-Dibromobiphenyl**: Bromines on opposite carbons (C₁ and C₄ or C₁' and C₄').

This gives us **3 unique isomers** for the same ring.

2. **Bromines on Different Rings:**
- **2,2'-Dibromobiphenyl**: Bromines on the same position of both rings (C₂ and C₂').
- **2,3'-Dibromobiphenyl**: Bromines on adjacent positions of different rings (C₂ and C₃').
- **2,4'-Dibromobiphenyl**: Bromines on opposite positions of different rings (C₂ and C₄').
- **3,3'-Dibromobiphenyl**: Bromines on the same position of both rings (C₃ and C₃').
- **3,4'-Dibromobiphenyl**: Bromines on adjacent positions of different rings (C₃ and C₄').

This gives us **6 unique isomers** for the different rings.

### Step 4: Total Isomers Calculation
Adding the isomers from both configurations:
- From the same ring: 3 isomers
- From different rings: 6 isomers

Total = 3 + 6 = **9 isomers**

### Conclusion
The total number of isomers of dibromobiphenyl is **9**.