If 3-chloromethylhexane is treated with `C_(2)H_(5)Ona//C_(2)H_(5)OH, E_(2)` elimination reaction takes place predominantly. How many different alkenes would be formed ?

Answer

To determine how many different alkenes can be formed when 3-chloromethylhexane undergoes an E2 elimination reaction, we will follow these steps:

### Step 1: Understand the Structure of 3-Chloromethylhexane
3-chloromethylhexane has the following structure:
- It is a hexane chain (6 carbon atoms) with a chlorine atom at the 3rd carbon and a methyl group also at the 3rd carbon.

### Step 2: Identify Alpha and Beta Carbons
In the E2 elimination reaction, we need to identify the alpha carbon (the one with the leaving group, Cl) and the beta carbons (the adjacent carbons).
- The alpha carbon is the 3rd carbon (C-3) where the chlorine is attached.
- The beta carbons are C-2, C-4, and C-5.

### Step 3: Determine Possible Eliminations
In an E2 reaction, a hydrogen atom from a beta carbon is removed along with the leaving group (Cl) from the alpha carbon to form a double bond. We will analyze each beta carbon:

1. **Elimination from C-2 (Beta 1)**:
- Remove H from C-2 and Cl from C-3.
- This forms an alkene: C2H5-CH=CH-CH2-CH3 (2-hexene).

2. **Elimination from C-4 (Beta 2)**:
- Remove H from C-4 and Cl from C-3.
- This forms an alkene: C2H5-CH2-CH=CH-CH3 (3-hexene).

3. **Elimination from C-5 (Beta 3)**:
- Remove H from C-5 and Cl from C-3.
- This forms an alkene: C2H5-CH2-CH2-CH=CH2 (1-hexene).

### Step 4: Identify Geometric Isomers
For the alkenes formed, we need to check if any of them can have geometric (cis/trans) isomers:
- **2-hexene** can exist as cis-2-hexene and trans-2-hexene (2 isomers).
- **3-hexene** does not have geometric isomers because the double bond is between two identical groups (CH2 and CH3).
- **1-hexene** does not have geometric isomers either.

### Step 5: Count the Unique Alkenes
Now we can summarize the alkenes formed:
1. **Cis-2-hexene**
2. **Trans-2-hexene**
3. **3-hexene**
4. **1-hexene**

### Final Count
Thus, the total number of different alkenes formed is **4**.

### Summary of Steps:
1. Identify the structure of 3-chloromethylhexane.
2. Identify alpha and beta carbons.
3. Determine possible eliminations from each beta carbon.
4. Check for geometric isomers.
5. Count the unique alkenes formed.