AIIMS2019Chemistry-Acidity and Basicity

AIIMS 2019 Chemistry Effect of Substituents MCQ Question

Type: MCQ-conceptual-Medium

Assertion: Hydroquinone is more acidic than resorcinol.

Reason: OH shows I− effect

A

If both assertion and reason are true and reason is the correct explanation of assertion.

B

If both assertion and reason are true but reason is not the correct explanation of assertion.

C

If assertion is true but reason is false.

D

If both assertion and reason are false.

Correct Answer

Option B

Detailed Explanation

The statement is incorrect because resorcinol (1,3-dihydroxybenzene) does exhibit a +M (mesomeric) effect due to the presence of hydroxyl groups, which stabilize the negative charge on the conjugate base, thereby increasing its acidity. In contrast, hydroquinone (1,4-dihydroxybenzene) also shows a +M effect, but this does not decrease its acidity; in fact, both compounds have similar acidity levels due to the resonance stabilization provided by their hydroxyl groups. Therefore, the assertion about their acidity trends is false. Options (A) and (C) are incorrect as they misinterpret the effects of the substituents, while (D) does not apply since there is a definitive evaluation of the statements.

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