Methyl oxirane on reaction with `CH_3 MgBr`, followed by hydrolysis, gives alcohol. By which of the following mechanisms does the reaction proceed ?

Options

A. `SN^1`
B. `SN^2`
C. `SN^i`
D. `SE`

Explanation

To determine the mechanism by which methyl oxirane reacts with methyl magnesium bromide (CH₃MgBr) followed by hydrolysis to form an alcohol, we can follow these steps:

### Step 1: Identify the Reactants
Methyl oxirane is an epoxide, which is a three-membered cyclic ether. The structure of methyl oxirane is as follows:

```
O
/ \
CH3 CH
```

### Step 2: Reaction with Methyl Magnesium Bromide
When methyl oxirane reacts with methyl magnesium bromide (a Grignard reagent), the nucleophilic carbon (from the Grignard reagent) attacks the less hindered carbon atom of the epoxide. This is a characteristic feature of an SN2 mechanism, where the nucleophile attacks the electrophile and simultaneously displaces the leaving group.

### Step 3: Mechanism of the Reaction
1. The nucleophilic carbon from CH₃MgBr attacks the carbon atom adjacent to the oxygen in the epoxide.
2. This results in the opening of the epoxide ring and the formation of a tetrahedral intermediate.
3. The oxygen atom becomes negatively charged, and the bond between the carbon and oxygen is broken.

### Step 4: Hydrolysis
After the epoxide ring opens, hydrolysis occurs. The negatively charged oxygen will react with water (or H₃O⁺) to form an alcohol. The final product will be a secondary alcohol due to the formation of a new carbon-carbon bond.

### Step 5: Final Product
The final product after hydrolysis is a secondary alcohol, which can be represented as follows:

```
OH
/
CH3-CH-CH3
```

### Conclusion
The mechanism by which methyl oxirane reacts with CH₃MgBr followed by hydrolysis is an SN2 mechanism, resulting in the formation of a secondary alcohol.