Which of the following is correct?

Options

A. Vinyl chloride is more reactive than ethyl chloride in `S_(N^(2))`
B. Vinyl chloride is more reactive than ethyl chloride in `S_(N^(1))`
C. allyl chloride is less reactive than n - propyl chloride in `S_(N^(1))`
D. allyl chloride is more reactive than n - propyl chloride in `S_(N^(2))`

Answer

To solve the question regarding the reactivity of vinyl chloride and allyl chloride in SN1 and SN2 reactions, we will analyze each statement provided in the question step by step.

### Step-by-Step Solution:

1. **Understanding Vinyl Chloride and Ethyl Chloride in SN2 Reactions:**
- Vinyl chloride (CH2=CHCl) has a chlorine atom attached to an sp2 hybridized carbon, while ethyl chloride (CH3CH2Cl) has chlorine attached to an sp3 hybridized carbon.
- In SN2 reactions, the nucleophile attacks the carbon atom from the opposite side of the leaving group (Cl). The sp2 hybridized carbon in vinyl chloride has more s-character (33.3%) compared to the sp3 hybridized carbon in ethyl chloride (25%).
- The higher s-character in vinyl chloride means that the bond between the carbon and chlorine is held more tightly, making it harder for the Cl to leave. Therefore, ethyl chloride is more reactive in SN2 than vinyl chloride.

**Conclusion:** The statement "vinyl chloride is more reactive than ethyl chloride in SN2" is **incorrect**.

2. **Understanding Vinyl Chloride and Ethyl Chloride in SN1 Reactions:**
- In SN1 reactions, the leaving group (Cl) departs first, forming a carbocation. In vinyl chloride, the carbocation formed after Cl leaves is less stable because it is on an sp2 carbon, which is more electronegative and holds the positive charge less favorably.
- In ethyl chloride, the carbocation formed (CH3CH2+) is more stable due to the inductive effect from the two alkyl groups (ethyl group) that help stabilize the positive charge.

**Conclusion:** The statement "vinyl chloride is more reactive than ethyl chloride in SN1" is **incorrect**.

3. **Understanding Allyl Chloride and n-Propyl Chloride in SN1 Reactions:**
- Allyl chloride (CH2=CHCH2Cl) can form a resonance-stabilized carbocation when Cl leaves. The positive charge can be delocalized over the double bond, increasing its stability.
- In contrast, n-propyl chloride (CH3CH2CH2Cl) forms a primary carbocation, which is less stable and does not benefit from resonance.

**Conclusion:** The statement "allyl chloride is less reactive than n-propyl chloride in SN1" is **incorrect**.

4. **Understanding Allyl Chloride and n-Propyl Chloride in SN2 Reactions:**
- In SN2 reactions, allyl chloride has a chlorine atom attached to a carbon that is part of a double bond (sp2), while n-propyl chloride has chlorine attached to an sp3 carbon.
- The transition state for allyl chloride benefits from resonance stabilization due to the adjacent double bond, making the reaction more favorable compared to n-propyl chloride, which lacks such stabilization.

**Conclusion:** The statement "allyl chloride is more reactive than n-propyl chloride in SN2" is **correct**.

### Final Answer:
The correct statement is: **Allyl chloride is more reactive than n-propyl chloride in SN2.**