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MCQMediumJEE 2023Reaction Mechanisms (Substitution, Addition, Elimination)

JEE Chemistry 2023 Question with Solution

In the following reaction, ‘A’ is:

Reaction scheme showing an amino alcohol substrate reacting with diethyl carbonate to form product A as major product.Embedded reaction image continuation showing reagent and product label A in the major product transformation.
  • A

    NH-C(=O)OEt\text{NH-C(=O)OEt}

  • B

    Option not available in scraped HTML

  • C

    Option not available in scraped HTML

  • D

    Option not available in scraped HTML

Answer

Correct answer:A

Step-by-step solution

Standard Method

Given: The reaction involves an amino alcohol substrate and formation of a major product A.

Find: Identify the structure of A.

The solution states that carbamates (R-NH-C(=O)OR’)\left(\text{R-NH-C(=O)OR'}\right) are commonly formed by reaction of primary amines with chloroformates. It further explains that the primary amine group attacks the carbonyl carbon of the reagent, leading to formation of a carbamate group.

Thus, the major product A is:

NH-C(=O)OEt\text{NH-C(=O)OEt}

the solution explicitly concludes that the correct option is A and identifies option (1) as the product. Since the listed options are unavailable, the answer is taken from the solution.

Therefore, the correct option is A.

Product structure image showing a five-membered cyclic carbamate corresponding to the correct answer option A.Mechanism image showing nucleophilic attack by amino group on carbonate carbonyl followed by cyclization to cyclic carbamate product.

Mechanistic Interpretation

Given: A substrate containing −NH2-NH_2 and −CH2OH-CH_2OH groups reacts to give major product A.

Find: The identity of the product formed.

From the extracted explanation:

  1. The lone pair on −NH2-NH_2 attacks the electrophilic carbonyl carbon.
  2. This forms a carbamoyl intermediate.
  3. The oxygen lone pair then attacks intramolecularly, producing a cyclic carbamate.

So the reaction does not leave the amine unchanged; instead it converts it into a carbamate functionality. The answer image corresponds to the cyclic carbamate shown as option A.

Hence, the correct option is A.

Common mistakes

  • Assuming the −OH-OH group reacts first is incorrect because the solution identifies nucleophilic attack by the −NH2-NH_2 group on the carbonyl carbon. First check which site is described as the attacking nucleophile.

  • Treating the product as a simple substitution product is wrong. The extracted mechanism shows cyclization, so the final product is a cyclic carbamate, not merely an acyclic derivative.

  • Relying on the answer key '(2)' would be misleading here. The solution explicitly says The Correct Option is A, so the worked solution must take precedence.

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