Assertion: -But-1-ene on reaction with HBr in the presence of a peroxide produces 1-bromobutane.
Reason :-It involves the formation of a primary radical.

Options

A. If both Assertion and Reason are CORRECT and Reason is the CORRECT explanation of the Assertion.
B. If both Assertion and Reason are CORRECT but Reason is not the CORRECT explanation of the Assertion.
C. If Assertion is CORRECT but Reason is INCORRECT.
D. If Assertion is INCORRECT but Reason is CORRECT.

Explanation

To analyze the assertion and reason provided in the question, we will break down the steps involved in the reaction of but-1-ene with HBr in the presence of a peroxide.

### Step-by-Step Solution:

1. **Understanding the Reaction**:
- The assertion states that but-1-ene reacts with HBr in the presence of a peroxide to produce 1-bromobutane.
- The reason given is that this reaction involves the formation of a primary radical.

2. **Reaction with Peroxide**:
- In the presence of peroxides (like ROOR), the reaction proceeds via a free radical mechanism rather than the usual ionic mechanism.
- The peroxide undergoes homolytic cleavage, producing two alkoxy radicals (RO•).

3. **Formation of Bromine Radical**:
- The alkoxy radical (RO•) reacts with HBr, leading to the formation of a bromine radical (Br•) and an alcohol (ROH).
- This step is crucial as it generates the bromine radical needed for the next step.

4. **Reaction of But-1-ene with Bromine Radical**:
- The structure of but-1-ene is CH2=CH-CH2-CH3.
- The bromine radical (Br•) then attacks the double bond of but-1-ene.
- The pi bond between the first and second carbon undergoes homolytic cleavage, resulting in the formation of a secondary radical (C2H5-CH•-CH2Br).

5. **Formation of 1-Bromobutane**:
- This secondary radical can then react with another HBr molecule.
- The radical combines with HBr to form 1-bromobutane (C4H9Br) and regenerate the bromine radical.

6. **Conclusion**:
- The assertion is correct: but-1-ene does produce 1-bromobutane when reacted with HBr in the presence of peroxide.
- The reason is incorrect: the reaction involves the formation of a secondary radical, not a primary radical.

### Final Answer:
- **Assertion**: True (but-1-ene produces 1-bromobutane).
- **Reason**: False (it involves the formation of a secondary radical, not a primary radical).