Assertion (A): Metamers can also be position or chain isomers.
Reason (R ): Tautomerism was introduced by `C.P`. Laar to explain the chemical reactivity of a substance according to two possible structrues.

Options

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

Explanation

To solve the assertion and reason question, we will analyze both the assertion (A) and the reason (R) step by step.

### Step 1: Analyze the Assertion (A)
The assertion states that "Metamers can also be position or chain isomers."

- **Definition of Metamerism**: Metamerism is a type of isomerism where compounds have the same molecular formula but differ in the arrangement of alkyl groups around a functional group.
- **Examples**: Metamerism is commonly observed in ethers, thioethers, and secondary amines. For instance, in ethers, different alkyl groups can be attached to the same oxygen atom, leading to different metamers.
- **Position and Chain Isomers**: Metamers can indeed exhibit positional or chain isomerism. If the functional group is part of a carbon chain, the carbon skeleton can vary on either side of the functional group, leading to different structural arrangements.

**Conclusion for Assertion (A)**: The assertion is true.

### Step 2: Analyze the Reason (R)
The reason states that "Tautomerism was introduced by C.P. Laar to explain the chemical reactivity of a substance according to two possible structures."

- **Definition of Tautomerism**: Tautomerism is a special type of isomerism where two or more isomers (tautomers) can readily interconvert, typically involving the relocation of a hydrogen atom and a shift of a double bond.
- **C.P. Laar's Contribution**: C.P. Laar did indeed contribute to the understanding of tautomerism, explaining how certain compounds can exist in two forms that are in equilibrium.
- **Relevance to Assertion**: While the statement about tautomerism is true, it does not directly relate to the assertion about metamers. Tautomerism and metamerism are different concepts in isomerism.

**Conclusion for Reason (R)**: The reason is true but does not explain the assertion.

### Final Conclusion
Both the assertion (A) and the reason (R) are true, but the reason does not provide a correct explanation for the assertion. Therefore, the correct answer is that both A and R are true, but R is not the correct explanation for A.

### Answer:
Both A and R are true, but R is not the correct explanation for A (Option B).

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