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MCQEasyJEE 2024Aldehydes & Ketones

JEE Chemistry 2024 Question with Solution

In the given reactions, identify the reagent A and reagent B: CH3−C≡CH+Na→A\mathrm{CH_3 - C\equiv CH + Na \rightarrow A} B→CH3−C≡C−CH2−CH2−CH3+NaBr\mathrm{B \rightarrow CH_3 - C\equiv C - CH_2 - CH_2 - CH_3 + NaBr}

  • A

    A-CrO₃, B-CrO₃

  • B

    A-CrO₃, B-CrO₂Cl₂

  • C

    A-CrO₂Cl₂, B-CrO₂Cl₂

  • D

    A-CrO₂Cl₂, B-CrO₃

Answer

Correct answer:B

Step-by-step solution

Standard Method

Given: We have to identify reagent A and reagent B.

Find: The correct pair of reagents corresponding to the reaction sequence.

From the solution, the conclusion explicitly states that reagent A is CrO3\text{CrO}_3 and reagent B is CrO2Cl2\text{CrO}_2\text{Cl}_2.

The solution concludes:

A−CrO3B−CrO2Cl2A-\text{CrO}_3 \qquad B-\text{CrO}_2\text{Cl}_2

Therefore, the correct option is B.

Note: The solution discusses a different reaction pathway involving toluene, benzylidene diacetate, and benzaldehyde, which does not match the given question text. However, both the solution heading and the answer key indicate Option B, so the answer is taken as B.

Common mistakes

  • Choosing reagents only by matching chromium compounds without checking the exact order of A and B is incorrect. The two reagents appear in different positions, so the order must be matched carefully. Always verify which reagent is assigned to A and which to B.

  • Assuming the detailed explanation in the solution matches the question can be misleading here. The displayed working refers to a different reaction system. Always check whether the reaction described in the solution is the same as the one asked before using its reasoning.

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