`1^(@)` alkyl halides preferably undergo which of the following mechanism ?

Options

A. `E_(1)`
B. `E_(1cb)`
C. `S_(N)1`
D. `S_(N)2`

Explanation

To determine which mechanisms primary alkyl halides preferably undergo, we need to analyze the characteristics of various mechanisms: E1, E1CB, SN1, and SN2.

### Step-by-Step Solution:

1. **Understanding Primary Alkyl Halides**:
- Primary alkyl halides are compounds where the halogen is attached to a primary carbon (a carbon bonded to only one other carbon).

2. **Analyzing the Mechanisms**:
- **E1 Mechanism**:
- This mechanism involves the formation of a carbocation intermediate.
- Stability of carbocations is crucial; tertiary carbocations are more stable than secondary, which are more stable than primary.
- Therefore, primary alkyl halides do not favor the E1 mechanism.

3. **E1CB Mechanism**:
- In this mechanism, a carbanion is formed instead of a carbocation.
- Primary carbanions are relatively stable compared to secondary and tertiary.
- Thus, primary alkyl halides can undergo the E1CB mechanism.

4. **SN1 Mechanism**:
- Similar to E1, the SN1 mechanism also involves the formation of a carbocation.
- Again, the stability of the carbocation is key. Since primary carbocations are the least stable, primary alkyl halides do not favor the SN1 mechanism.

5. **SN2 Mechanism**:
- In this mechanism, the reaction occurs in a single step where the nucleophile attacks the carbon atom, displacing the leaving group.
- The rate of the SN2 reaction is inversely proportional to steric hindrance.
- Since primary alkyl halides have less steric hindrance, they are most favorable for the SN2 mechanism.

6. **Conclusion**:
- Based on the analysis, primary alkyl halides preferably undergo the E1CB and SN2 mechanisms.

### Final Answer:
Primary alkyl halides preferably undergo the E1CB and SN2 mechanisms.