A : Generally, n-hexane and onwards can be sulphonated but isobutane and isopentane can also be sulphonated.
R : Isobutane and isopentane can produce tertiary free radical.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1).
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2)
C. if Assertion is true statement but Reason is false, then mark (3)
D. If both Assertion and Reason are false statements, then mark (4)

Answer

To solve the question, we need to analyze the assertion (A) and reasoning (R) provided:

### Assertion (A):
"Generally, n-hexane and onwards can be sulphonated but isobutane and isopentane can also be sulphonated."

### Reasoning (R):
"Isobutane and isopentane can produce tertiary free radical."

### Step-by-Step Solution:

1. **Understanding Sulphonation**:
- Sulphonation is a chemical reaction where a sulfonyl group (−SO3H) is introduced into an organic compound. For alkanes, this reaction typically requires the presence of concentrated sulfuric acid (H2SO4).

2. **Analyzing the Assertion**:
- The assertion states that n-hexane (C6H14) and higher alkanes can be sulphonated. This is true because larger alkanes can stabilize the formation of free radicals due to their higher number of carbon atoms.
- Isobutane (C4H10) and isopentane (C5H12) can also be sulphonated. This is significant because they are branched alkanes, which can stabilize free radicals.

3. **Analyzing the Reasoning**:
- The reasoning states that isobutane and isopentane can produce tertiary free radicals. This is also true:
- Isobutane has a structure where the central carbon is tertiary (attached to three other carbon atoms), allowing it to form a stable tertiary free radical.
- Isopentane can also form a tertiary free radical under similar conditions.

4. **Conclusion**:
- Both the assertion and reasoning are true. The assertion correctly states the sulphonation capabilities of n-hexane and higher alkanes, as well as isobutane and isopentane. The reasoning correctly explains why isobutane and isopentane can undergo sulphonation due to the formation of stable tertiary free radicals.

### Final Answer:
Both the assertion (A) and reasoning (R) are true, and the reasoning correctly explains the assertion.