The number of isomers possible for disubstituted borazine, `B_(3)N_(3)H_(4)X_(2)` is

Options

A. 3
B. 4
C. 6
D. 5

Answer

To determine the number of isomers possible for disubstituted borazine, \( B_3N_3H_4X_2 \), we need to analyze the structure of borazine and the positions where the substituents (X) can be placed.

### Step-by-Step Solution:

1. **Understanding the Structure of Borazine**:
- Borazine has a cyclic structure composed of alternating boron (B) and nitrogen (N) atoms, with hydrogen (H) atoms attached to these atoms. The general formula is \( B_3N_3H_6 \), but when we substitute two hydrogens with two halogen atoms (X), we get \( B_3N_3H_4X_2 \).

2. **Identifying Possible Substitution Positions**:
- In the borazine ring, there are three boron and three nitrogen atoms. The positions where we can place the substituents (X) are:
- Ortho (adjacent positions)
- Meta (one atom apart)
- Para (opposite positions)

3. **Case 1: Both Substituents in Ortho Position**:
- If both substituents are on adjacent boron or nitrogen atoms, this gives us one isomer.

4. **Case 2: Both Substituents in Meta Position**:
- If both substituents are placed on boron atoms, this gives one isomer.
- If both are placed on nitrogen atoms, this gives another isomer.
- If one is on a boron and the other on a nitrogen, this gives a third isomer.

5. **Case 3: One Substituent on Boron and One on Nitrogen**:
- This can occur in two ways: one substituent can be on a boron atom while the other is on a nitrogen atom, which gives us another isomer.

6. **Counting the Isomers**:
- From the above cases, we have:
- 1 isomer from ortho substitution.
- 3 isomers from meta substitution (both on boron, both on nitrogen, one on boron and one on nitrogen).
- 1 isomer from para substitution (one on boron and one on nitrogen).
- Adding these together gives us a total of 5 isomers.

### Final Answer:
The number of isomers possible for disubstituted borazine, \( B_3N_3H_4X_2 \), is **5**.