JEE Main · Chemistry → Steady

Aldehydes, Ketones and Carboxylic Acids appeared 46 times across 3 years — 5.3% of Chemistry. This question is from Oxidation of Alcohols and Alkene Reactions.

Year	2026	2025	2024	Total
Questions	14	21	11	46

Practice all Aldehydes, Ketones and Carboxylic Acids questions → View full JEE Main weightage & trends →

The image shows an organic conversion from a bromo-substituted cyclopentene to a carboxylic acid derivative.
The correct sequence of reagents for the above conversion of X to Y is :

A. $(i) NaOH (aq) (ii) Jones reagent (iii) H₃O⁺$
B. $(i) B₂H₆ / H₂O₂ (ii) NaOEt (iii) Jones reagent$
C. $(i) Jones reagent (ii) NaOEt (iii) Hot KMnO₄ /KOH$
D. $(i) NaOEt (ii) B₂H₆/H₂O₂ (iii) Jones reagent$

Solution & Explanation

Core Logic

The transformation requires converting a cyclic bromoalkane into a conjugated cyclic carboxylic acid. The steps required are elimination to form an alkene, anti-Markovnikov hydration to an alcohol, and finally oxidation.

Step 1: Elimination

Treating the starting material with NaOEt (a strong base) promotes an E2 elimination, forming a conjugated diene in the cyclopentane ring.

Oxidation of Alcohols and Alkene Reactions diagram for Q54 - JEE Main 2026 Morning — The image shows an organic conversion from a bromo-substituted cyclopentene to a carboxylic acid derivative.

Step 2: Hydroboration-Oxidation

Using $B₂H₆ / H₂O₂$ $B_2H_6 / H_2O_2$ (Hydroboration-oxidation) adds water across the less hindered double bond in an anti-Markovnikov fashion, placing an -OH group on the terminal carbon attached to the ring.

Step 3: Strong Oxidation

Finally, utilizing Jones reagent ( $CrO₃ / H^+$ $CrO_3 / H^+$) strongly oxidizes the primary alcohol directly into a carboxylic acid ( $-COOH$ $-COOH$), yielding the desired product Y.

Oxidation of Alcohols and Alkene Reactions diagram for Q54 - JEE Main 2026 Morning — The image shows an organic conversion from a bromo-substituted cyclopentene to a carboxylic acid derivative.

Pattern Recognition

Formation of a new double bond alongside chain functionalization generally implies Base-catalyzed E2 followed by functional group addition (like hydroboration) and terminal oxidation.

Chapter Mix

Class 12 Chemistry: Aldehydes Ketones and Carboxylic Acids Class 11 Chemistry: Hydrocarbons Class 12 Chemistry: Alcohols Phenols and Ethers

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 $-OH$ $-OH$ group (acidic) and an aldehyde group (electrophilic).

When one equivalent of Grignard reagent ( $PhMgBr$ $PhMgBr$) 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 $-OH$ $-OH$ reacts with $PhMgBr$ $PhMgBr$:

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

Upon workup with $aq. NH₄Cl$ $aq. NH_4Cl$, 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_2026_23_january_morning

Practice all Aldehydes Ketones and Carboxylic Acids previous-year questions →

SYSTEM

Syllabus Analysis & Trend Mapping

Dashboard Chapter Trends Formula Recognition Questions Feed Weightage

Rankbit System

JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%) | JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%)