The number of structurally isomerc tribromo derivatives possible for benzene are:

Options

A. 2
B. 3
C. 4
D. 5

Explanation

To determine the number of structurally isomeric tribromo derivatives possible for benzene, we can follow these steps:

### Step 1: Understand the Structure of Benzene
Benzene is a cyclic compound with the formula C₆H₆. It has a planar structure with alternating double bonds, and each carbon atom is bonded to one hydrogen atom.

### Step 2: Identify the Substitution Positions
When we talk about tribromo derivatives, we are referring to benzene where three hydrogen atoms have been replaced by bromine atoms. The positions of these bromine substitutions can lead to different isomers.

### Step 3: Determine Possible Substitution Patterns
We need to consider the different ways we can place three bromine atoms on the benzene ring. The positions on the benzene ring can be numbered as follows:

1. Position 1 (C1)
2. Position 2 (C2)
3. Position 3 (C3)
4. Position 4 (C4)
5. Position 5 (C5)
6. Position 6 (C6)

### Step 4: List the Isomeric Structures
1. **1,2,3-Tribromobenzene**: Bromines are on positions 1, 2, and 3.
2. **1,2,4-Tribromobenzene**: Bromines are on positions 1, 2, and 4.
3. **1,3,5-Tribromobenzene**: Bromines are on positions 1, 3, and 5.

### Step 5: Check for Equivalent Structures
When placing the bromines, we must ensure that we do not count equivalent structures multiple times. For example, placing bromines at positions 1, 2, and 4 is distinct from placing them at 1, 3, and 5, but placing them at 1, 2, and 3 is the same as placing them at 2, 3, and 1 due to the symmetry of the benzene ring.

### Conclusion
After analyzing the possible positions for bromine substitution, we find that there are three unique structurally isomeric tribromo derivatives of benzene:

1. 1,2,3-Tribromobenzene
2. 1,2,4-Tribromobenzene
3. 1,3,5-Tribromobenzene

Thus, the total number of structurally isomeric tribromo derivatives possible for benzene is **3**.

---