From how many alkyl halide we get pentane on reaction with
Zn + HCl (only structural isomers)

Options

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

Answer

To determine how many structural isomers of alkyl halides can yield pentane upon reaction with zinc and hydrochloric acid, we will follow these steps:

### Step 1: Understand the Reaction
The reaction involves the reduction of alkyl halides (R-X) using zinc (Zn) and hydrochloric acid (HCl) to produce alkanes (R-H) and zinc halide (ZnX). Since we want to obtain pentane (C5H12), we need to consider alkyl halides that can yield this molecular formula.

**Hint:** Remember that structural isomers have the same molecular formula but different structural arrangements.

### Step 2: Identify the Alkyl Halides
We need to identify alkyl halides that have five carbon atoms (C5) and can be represented in different structural forms. The general formula for pentane is C5H12, which means we need to consider halides that can be derived from pentane.

### Step 3: List the Possible Structural Isomers
1. **1-Chloropentane**:
- Structure: CH3-CH2-CH2-CH2-CH2Cl
- This is the straight-chain alkyl halide.

2. **2-Chloropentane**:
- Structure: CH3-CH2-CH(Cl)-CH2-CH3
- The chlorine is attached to the second carbon.

3. **3-Chloropentane**:
- Structure: CH3-CH(Cl)-CH2-CH2-CH3
- The chlorine is attached to the third carbon.

### Step 4: Verify for Additional Isomers
We need to ensure that there are no other structural isomers that can be formed. For example, if we try to place the chlorine on the fourth carbon, it would yield the same compound as 2-chloropentane due to symmetry. Therefore, we cannot count it as a new isomer.

### Step 5: Conclusion
The total number of structural isomers of alkyl halides that can yield pentane upon reduction with Zn and HCl is three:
1. 1-Chloropentane
2. 2-Chloropentane
3. 3-Chloropentane

### Final Answer
**Three structural isomers of alkyl halides can yield pentane.**

---