Which of the following products can be formed when 2 -chloro -2- methylpentane reacts with sodium methoxide in methanol?
1. `C_(2)H_(5)CH_(2)overset(CH_(2))overset("| ")underset(CH_(3))underset("| ")"C "-OCH_(3)`
2. `C_(2)H_(5)CH_(2)underset(CH_(3))underset("| ")"C "=CH_(2)`
3. `C_(2)H_(5)CH=underset(CH_(3))underset("| ")"C "-CH_(3)`

Options

A. 3 only
B. 1 and 2
C. 1 and 2
D. 1, 2 and 3

Answer

To solve the problem of what products can be formed when 2-chloro-2-methylpentane reacts with sodium methoxide in methanol, we will follow these steps:

### Step 1: Understand the Reactants
We have 2-chloro-2-methylpentane, which has the structure:
```
CH3
|
CH3-CH2-C-CH2-CH3
|
Cl
```
This compound has a chlorine atom (Cl) attached to a tertiary carbon.

### Step 2: Identify the Reaction Conditions
The reaction is taking place in the presence of sodium methoxide (CH3O-) in methanol (CH3OH). Sodium methoxide is a strong nucleophile and can also act as a base.

### Step 3: Determine the Mechanism
Since 2-chloro-2-methylpentane is a tertiary alkyl halide, it can undergo two types of reactions:
1. **SN1 Reaction**: Substitution reaction where the nucleophile (methoxide ion) attacks the carbocation formed after the leaving group (Cl) departs.
2. **E1 Reaction**: Elimination reaction where a hydrogen atom is removed from the adjacent carbon, leading to the formation of a double bond.

### Step 4: Formation of Carbocation
When Cl leaves, it forms a stable tertiary carbocation:
```
CH3
|
CH3-CH2-C^+ -CH2-CH3
```

### Step 5: SN1 Reaction Product
In the SN1 mechanism, the methoxide ion (CH3O-) attacks the carbocation:
```
CH3
|
CH3-CH2-C-OCH3
```
This gives the product:
1. **Product 1**: `C2H5CH2C(OCH3)CH3`

### Step 6: E1 Reaction Products
For the E1 mechanism, we can eliminate a hydrogen atom from one of the adjacent carbons to form alkenes. There are two possible eliminations:
1. **Elimination from the first carbon (CH2)**:
- This leads to:
```
CH3
|
CH3-CH2-C=CH2
```
**Product 2**: `C2H5CH2C=CH2`

2. **Elimination from the second carbon (CH)**:
- This leads to:
```
CH3
|
CH3-C=CH-CH2-CH3
```
**Product 3**: `C2H5CH=CHC(CH3)`

### Step 7: Summary of Products
The products formed from the reaction of 2-chloro-2-methylpentane with sodium methoxide in methanol are:
1. `C2H5CH2C(OCH3)CH3` (from SN1)
2. `C2H5CH2C=CH2` (from E1)
3. `C2H5CH=CHC(CH3)` (from E1)

### Conclusion
All three products can be formed during the reaction. Therefore, the answer is that all options (1, 2, and 3) are correct.