Chlorination of allylic hydrogen is difficult than vinylic hydrogen.
Allyl radical is stabilished by resonance.

Options

A. If both `(A)` and `(R )` are true, but `( R)` is the correct explanation of `(A)`
B. If both `(A)` and `( R)` are true, but `(R )` is not the correct explanation of `(A)`.
C. If `(A)` is true but `( R)` is false.
D. If `(A)` is false but `( R)` is true.

Explanation

To solve the question regarding the chlorination of allylic and vinylic hydrogens, we will analyze the assertion and reason provided in the statement.

### Step-by-Step Solution:

1. **Understanding Allylic and Vinylic Hydrogens**:
- **Allylic Hydrogen**: These are hydrogens attached to a carbon atom that is adjacent to a carbon-carbon double bond (C=C). For example, in propene (CH2=CH-CH3), the hydrogens on the CH2 group next to the double bond are allylic.
- **Vinylic Hydrogen**: These are hydrogens that are directly attached to the carbon atom of a carbon-carbon double bond. In the same example of propene, the hydrogens on the CH2 group of the double bond are vinylic.

2. **Chlorination Reaction**:
- Chlorination involves the substitution of hydrogen atoms with chlorine atoms. The first step in this reaction is the formation of free radicals.

3. **Formation of Free Radicals**:
- When allylic hydrogen is chlorinated, an allylic radical is formed. This radical can be represented as follows:
\[ \text{Allylic Radical: } \text{R-CH=CH-CH}_2^{\cdot} \]
- This radical is stabilized by resonance. The allylic radical can delocalize the unpaired electron over the adjacent double bond, leading to resonance structures.

4. **Resonance Stabilization**:
- The allylic radical can be represented by multiple resonance structures, which distribute the radical character across the molecule, enhancing its stability.

5. **Vinylic Radical Formation**:
- In contrast, when vinylic hydrogen is chlorinated, a vinylic radical is formed:
\[ \text{Vinylic Radical: } \text{R-CH=CH}^{\cdot} \]
- This radical is less stable because it is formed on an sp² hybridized carbon, which is more electronegative and less capable of stabilizing the radical due to the lack of resonance stabilization.

6. **Comparison of Stability**:
- The allylic radical is more stable due to resonance, while the vinylic radical is less stable because it lacks this resonance stabilization. Therefore, chlorination of allylic hydrogens is more favorable than that of vinylic hydrogens.

7. **Conclusion**:
- The assertion that "chlorination of allylic hydrogen is more difficult than vinylic hydrogen" is **false**. The reason that "allylic radical is stabilized by resonance" is **true**. Thus, the correct answer to the assertion and reason question is that the assertion is false, but the reason is correct.

### Final Answer:
- Assertion: False
- Reason: True
- Correct Answer: D