Which alkyl chloride shows highest probability of SN1 mechanism?

Options

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

Answer

To determine which alkyl chloride shows the highest probability of undergoing an SN1 mechanism, we need to analyze the stability of the carbocations formed during the reaction. The SN1 mechanism involves two main steps: the formation of a carbocation intermediate and the subsequent nucleophilic attack.

### Step-by-Step Solution:

1. **Understanding SN1 Mechanism**:
- The SN1 (Substitution Nucleophilic Unimolecular) reaction is a two-step process. The first step involves the formation of a carbocation after the leaving group departs, and the second step involves the nucleophile attacking the carbocation.

2. **Identify the Alkyl Chlorides**:
- Consider the following alkyl chlorides:
- CH3Cl (Methyl chloride)
- CH3CH2Cl (Ethyl chloride)
- (CH3)3CCl (Tert-butyl chloride)
- CH3CH(CH3)Cl (Isopropyl chloride)

3. **Formation of Carbocations**:
- When the leaving group (Cl-) departs, it generates a carbocation:
- CH3Cl → CH3+ (Methyl carbocation)
- CH3CH2Cl → CH3CH2+ (Ethyl carbocation)
- (CH3)3CCl → (CH3)3C+ (Tert-butyl carbocation)
- CH3CH(CH3)Cl → CH3C+(CH3) (Isopropyl carbocation)

4. **Stability of Carbocations**:
- Carbocation stability increases with the number of alkyl groups attached to the positively charged carbon due to hyperconjugation and inductive effects.
- Tertiary carbocations ((CH3)3C+) are more stable than secondary (CH3C+(CH3)) and primary (CH3+) carbocations because they have three alkyl groups that can donate electron density to the positively charged carbon.

5. **Conclusion**:
- Among the given alkyl chlorides, the tert-butyl chloride ((CH3)3CCl) will form the most stable carbocation ((CH3)3C+), thus showing the highest probability of undergoing an SN1 reaction.

### Answer:
The alkyl chloride that shows the highest probability of SN1 mechanism is **(CH3)3CCl (Tert-butyl chloride)**.