PYQSide ExamsMy practice

Aldehydes, Ketones and Carboxylic Acids · Question 20

JEE Main 2026 (Online) 23rd January Evening ShiftNumericalMedium📈 Topic in 32% papers+4
1

Consider the following reaction of benzene. [figure] In compound (Q), the percentage of oxygen is %. (Nearest integer)

Answer

10

Solution

Step 1 (Friedel–Crafts acylation): the acyl chloride end (-COCl) acylates benzene in the presence of anhydrous AlCl3, giving P (1-phenylpentane-1,4-dione), C6H5COCH2CH2COCH3.

Step 2 (intramolecular aldol condensation): P is a 1,4-diketone. With aq NaOH the carbanion formed at the terminal CH3 attacks the C=O carbon attached to the ring, giving a five-membered ring; on heating, the aldol loses H2O to give a conjugated enone.

[figure]

Q = 3-phenylcyclopent-2-en-1-one, C11H10O

Molar mass = 11(12) + 10(1) + 16 = 158 g mol-1

\% O = 16158 100 = 10.13\% 10

Answer: 10

JEE Main 2026 (Online) 23rd January Evening Shift

Keep practising — Aldehydes, Ketones and Carboxylic Acids

2

Match the LIST-I with LIST-II Choose the correct answer from the options given below :

  1. A-IV, B-III, C-II, D-I
  2. A-III, B-I, C-IV, D-II
  3. A-II, B-I, C-IV, D-III
  4. A-III, B-IV, C-I, D-II
JEE Main 2026 (Online) 22nd January Morning Shift
3

The compound A, C8H8O2 reacts with acetophenone to form a single product via cross-Aldol condensation. The compound A on reaction with conc. NaOH forms a substituted benzyl alcohol as one of the two products. The compound A is :

  1. 2-hydroxy acetophenone
  2. 4-hydroxy benzaldehyde
  3. 4-methyl benzoic acid
  4. 4-methoxy benzaldehyde
JEE Main 2026 (Online) 22nd January Evening Shift
4

An organic compound "P" of molecular formula C6H12O3 gives positive iodoform test but negative Tollens' test. When "P" is treated with dilute acid, it produces "Q". "Q" gives positive Tollens' test and also iodoform test. The structure of "P" is :

  1. H- O \|C-CH2-CH2- OCH3 |CH-OCH3
  2. CH3- O \|C- OCH3 |CH- OCH3 |CH2
  3. CH3- O \|C-CH2- OCH3 |CH-OCH3
  4. CH3- O \|C- OCH3 | OCH3 |C-CH3
JEE Main 2026 (Online) 21st January Morning Shift
5

Match List - I with List - II. Choose the correct answer from the options given below :

  1. A-II, B-III, C-IV, D-I
  2. A-IV, B-III, C-I, D-II
  3. A-IV, B-I, C-II, D-III
  4. A-II, B-IV, C-I, D-III
JEE Main 2026 (Online) 21st January Evening Shift
6

A [(ii) H3O+](i) NaOH B [(ii) H2SO4, ](i) EtOH C 'A' shows positive Lassaigne's test for N and its molar mass is 121. 'B' gives effervescence with aq NaHCO3. 'C' gives fruity smell. Identify A, B and C from the following.

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
JEE Main 2025 (Online) 8th April Evening Shift
7

When [figure] undergoes intramolecular aldol condensation, the major product formed is :

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
JEE Main 2025 (Online) 8th April Evening Shift
8

Which of the following compounds is least likely to give effervescence of CO2 in presence of aq. NaHCO3?

  1. Ph- NH3 Cl
  2. [figure]
  3. [figure]
  4. [figure]
JEE Main 2025 (Online) 7th April Morning Shift
9

"P" is an optically active compound with molecular formula C6H12O. When "P" is treated with 2,4-dinitrophenylhydrazine, it gives a positive test. However, in presence of Tollens' reagent, "P" gives a negative test. Predict the structure of "P".

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
JEE Main 2025 (Online) 7th April Evening Shift
10

Aldol condensation is a popular and classical method to prepare , -unsaturated carbonyl compounds. This reaction can be both intermolecular and intramolecular. Predict which one of the following is not a product of intramolecular aldol condensation?

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
JEE Main 2025 (Online) 4th April Morning Shift
11

Which among the following compounds give yellow solid when reacted with NaOI/NaOH? Choose the correct answer from the options given below :

  1. (A) and (C) Only
  2. (C) and (D) Only
  3. (B), (C) and (E) Only
  4. (A), (C) and (D) Only
JEE Main 2025 (Online) 4th April Evening Shift

All Aldehydes, Ketones and Carboxylic Acids PYQs →

PDFDownload Aldehydes, Ketones and Carboxylic Acids PYQs as PDF Free, with answer key and a QR code to every solution — print it or study offline⬇
All JEE Main Chemistry chapters
Physical ChemistrySome Basic Concepts of ChemistryStructure of AtomStates of MatterThermodynamicsEquilibriumRedox ReactionsSolutionsElectrochemistryChemical Kinetics
Inorganic ChemistryClassification of Elements and Periodicity in PropertiesChemical Bonding and Molecular Structurep-Block Elements (Group 13 & 14)p-Block Elements (Group 15–18)d- and f-Block ElementsCoordination Compounds
Organic ChemistryOrganic Chemistry – Some Basic Principles and TechniquesIsomerismHydrocarbonsHaloalkanes and HaloarenesAlcohols, Phenols and EthersAldehydes, Ketones and Carboxylic AcidsAminesBiomoleculesPrinciples Related to Practical Chemistry