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Aldehydes, Ketones and Carboxylic Acids appeared 46 times across 3 years — 5.4% of Chemistry. This question is from Chemical Reactions of Ketones.

Year 2026 2025 2024 Total
Questions 14 21 11 46
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The product (A) formed in the following reaction sequence is : C H _ 3 - C ≡ C H [ (i i) H _ 2 / N i ](i) H g ^ 2 +, H _ 2 S O _ 4 (A)

Solution & Explanation

Core Logic

Breaking down the multi-step reaction path sequence:

  • Hydration of propyne using Kucherov's trigger condition (Hg²⁺, H₂SO₄) adds water across the triple bond via Markovnikov's rule. The intermediate enol undergoes tautomerization to yield acetone (CH₃-CO-CH₃).
  • Reacting acetone with HCN drives nucleophilic addition at the carbonyl carbon, forming a cyanohydrin intermediate: CH₃-C(OH)(CH₃)-CN.
  • Introducing a reducing agent (H₂/Ni) selectively converts the nitrile group (-CN) into a primary amine side chain (-CH₂-NH₂).

    • The final synthesized structure is: CH₃-C(OH)(CH₃)-CH₂-NH₂.

    Chemical Reactions of Ketones step sequence product chart for Q45
    Chemical Reactions of Ketones step sequence product chart for Q45

Pattern Recognition

Alkyne hydration produces a ketone carbonyl system. Cyanohydrin synthesis introduces a carbon coordinate, which subsequently reduces to a primary aliphatic amine functional group.

Chapter Mix

Class 12 Chemistry: Aldehydes, Ketones and Carboxylic Acids

Reference Study Guides

Aldehydes Ketones And Carboxylic Acids

More Aldehydes, Ketones and Carboxylic Acids Previous-Year Questions — Page 10

Q jee_main_2024_31_jan_morning Reactions with Grignard Reagent
The product of the following reaction is P.
Reactions with Grignard Reagent diagram for Q84 - JEE Main 2024 Morning
The image shows p-hydroxybenzaldehyde reacting with one equivalent of PhMgBr followed by aqueous ammonium chloride.
The number of hydroxyl groups present in the product P is
Numerical Answer. Answer: 0 to 0

Solution

Core Logic

The given reactant is p-hydroxybenzaldehyde, which contains both a phenolic -OH group (acidic) and an aldehyde group (electrophilic).

When one equivalent of Grignard reagent (PhMgBr) is added, it behaves primarily as a strong base due to the presence of an acidic proton. Acid-base reactions are extremely fast compared to nucleophilic additions.

The acidic phenolic -OH reacts with PhMgBr:

PhMgBr + HO-C₆H₄-CHO arrow Ph-H (Benzene) + BrMg-O-C₆H₄-CHO

Upon workup with aq. NH₄Cl, the phenoxide ion simply regenerates the starting p-hydroxybenzaldehyde. However, the question asks for the number of hydroxyl groups present in the formed product (Benzene).

Reactions with Grignard Reagent diagram for Q84 - JEE Main 2024 Morning
The image shows p-hydroxybenzaldehyde reacting with one equivalent of PhMgBr followed by aqueous ammonium chloride.

The distinct product formed in the reaction is Benzene. Benzene has 0 hydroxyl groups.

Pattern Recognition

Whenever a Grignard reagent encounters a molecule with an acidic hydrogen (alcohol, phenol, amine, alkyne), it will invariably act as a base first. If only 1 equivalent is used, nucleophilic addition to carbonyls will NOT happen.

Chapter Mix

Class 12 Chemistry: Aldehydes, Ketones and Carboxylic Acids Class 12 Chemistry: Alcohols, Phenols and Ethers

More Aldehydes, Ketones and Carboxylic Acids Questions — jee_main_2025_24_jan_morning

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