In which alkyl halide `SN^(2)` mechanism is favoured maximum

Options

A. `CH_(3)`Cl
B. `CH_(3)CH_(2)`Cl
C. `(CH_(3))_(2)`CHCl
D. `(CH_(3))_(3)`C -Cl

Answer

To determine which alkyl halide favors the SN2 mechanism the most, we need to analyze the characteristics of the SN2 reaction and the structure of various alkyl halides.

### Step-by-Step Solution:

1. **Understanding SN2 Mechanism**:
- The SN2 (Substitution Nucleophilic Bimolecular) mechanism involves a nucleophile attacking the electrophilic carbon from the opposite side of the leaving group (halide).
- This results in a backside attack, leading to a transition state where the bond between the carbon and the halide is partially broken while a new bond with the nucleophile is partially formed.

2. **Factors Affecting SN2 Reaction**:
- The steric hindrance around the carbon atom is a crucial factor. The less hindered the carbon is, the more favorable the SN2 reaction will be.
- Primary (1°) alkyl halides are less hindered compared to secondary (2°) and tertiary (3°) alkyl halides.

3. **Identifying Alkyl Halides**:
- Let's consider some examples of alkyl halides:
- **Methyl Chloride (CH3Cl)**: This is a primary halide with no steric hindrance.
- **Ethyl Chloride (C2H5Cl)**: This is also a primary halide but has slightly more steric hindrance than methyl chloride.
- **Isopropyl Chloride (C3H7Cl)**: This is a secondary halide and is more hindered.
- **Tert-Butyl Chloride (C4H9Cl)**: This is a tertiary halide and is highly hindered.

4. **Comparing the Alkyl Halides**:
- Among the alkyl halides mentioned:
- Methyl chloride (CH3Cl) is the least hindered.
- Ethyl chloride (C2H5Cl) is also primary but has more steric hindrance than methyl chloride.
- Isopropyl chloride (C3H7Cl) and tert-butyl chloride (C4H9Cl) are secondary and tertiary respectively, which are more hindered.

5. **Conclusion**:
- Since the SN2 mechanism is favored in less hindered alkyl halides, methyl chloride (CH3Cl) will favor the SN2 mechanism the most due to its minimal steric hindrance.

### Final Answer:
The alkyl halide that favors the SN2 mechanism the most is **Methyl Chloride (CH3Cl)**.