In the following questions, a statement of assertion (A) is following by a statement of reason (R )
A : primary alkyl halides on oxidation with DMSO gives aldehydes.
R : DMSO is used as polar aprotic solvent .

Options

A. If both Assertion & Reason are 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 the reason (R) provided:

### Assertion (A):
**Primary alkyl halides on oxidation with DMSO give aldehydes.**

### Reason (R):
**DMSO is used as a polar aprotic solvent.**

### Step-by-Step Solution:

1. **Understanding the Assertion:**
- Primary alkyl halides can be oxidized to aldehydes. This is a well-known reaction in organic chemistry, particularly involving the use of DMSO (Dimethyl sulfoxide) as an oxidizing agent.
- The process typically involves the reaction of a primary alkyl halide (e.g., RCH2X, where X is a halogen) with DMSO in the presence of a base, leading to the formation of an aldehyde (RCHO).

2. **Mechanism of the Reaction:**
- In the presence of a base, DMSO can facilitate the removal of the halide ion (X-) from the primary alkyl halide.
- The mechanism involves nucleophilic attack by the oxygen atom of DMSO on the carbon atom bonded to the halogen, resulting in the formation of an intermediate.
- The base then abstracts a proton from the intermediate, leading to the formation of the aldehyde and dimethyl sulfide as a byproduct.

3. **Understanding the Reason:**
- DMSO is classified as a polar aprotic solvent. This means it has a significant dipole moment (making it polar) but does not have acidic hydrogen atoms that can participate in hydrogen bonding (making it aprotic).
- Polar aprotic solvents are known to solvate cations effectively but do not stabilize anions through hydrogen bonding, which is beneficial in certain reactions, including the oxidation of alkyl halides.

4. **Evaluating the Relationship between A and R:**
- While both statements are true, the reason (R) does not directly explain why primary alkyl halides oxidize to aldehydes when using DMSO. The property of DMSO being a polar aprotic solvent is relevant, but it does not specifically justify the oxidation process leading to aldehyde formation.

### Conclusion:
- Both the assertion (A) and the reason (R) are correct.
- However, the reason (R) is not the correct explanation for the assertion (A).

### Final Answer:
- The correct option is: **Both A and R are true, but R is not the correct explanation for A.**