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Aldehydes, Ketones and Carboxylic Acids

JEE Main 2026 (Online) 21st January Morning ShiftMCQMedium📈 Topic in 10% papers+4−1
Ques. 1JEE Main 2026, 21 January (Morning Shift)

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

Answer

(3) CH3- O \|C-CH2- OCH3 |CH-OCH3

Solution

P gives a positive iodoform test P contains CH3-CO-.

P gives a negative Tollens' test P has no free –CHO group.

Q (formed by dilute acid) gives a positive Tollens' test a –CHO group is set free on hydrolysis P contains an acetal group, -CH(OCH3)2.

For option (3): CH3COCH2CH(OCH3)2 ( C6H12O3 ✓)

CH3COCH2CH(OCH3)2 + H2O H+ CH3COCH2CHO + 2CH3OH

Q = CH3COCH2CHO has –CHO (Tollens' test positive) and CH3CO- (iodoform test positive). ✓

(1) has a free –CHO group (Tollens' test positive) and no CH3CO- group.

(2) contains only ether linkages, which are not hydrolysed by dilute acid no aldehyde is formed.

(4) is a ketal; hydrolysis gives CH3COCOCH3, a diketone with no –CHO group.

Answer: (3)

Keep practising — Aldehydes, Ketones and Carboxylic Acids

Ques. 2JEE Main 2026, 21 January (Evening Shift)

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
Ques. 3JEE Main 2025, 8 April (Evening Shift)

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]
Ques. 4JEE Main 2025, 8 April (Evening Shift)

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

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
Ques. 5JEE Main 2025, 7 April (Morning Shift)

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]
Ques. 6JEE Main 2025, 7 April (Evening Shift)

"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]
Ques. 7JEE Main 2025, 4 April (Morning Shift)

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]
Ques. 8JEE Main 2025, 4 April (Evening Shift)

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
Ques. 9JEE Main 2025, 3 April (Morning Shift)

Number of molecules from below which cannot give iodoform reaction is : Ethanol, Isopropyl alcohol, Bromoacetone, 2-Butanol, 2-Butanone, Butanal, 2-Pentanone, 3-Pentanone, Pentanal and 3-Pentanol.

  1. 4
  2. 3
  3. 5
  4. 2
Ques. 10JEE Main 2025, 3 April (Evening Shift)

The major product (P) in the following reaction is : Ph- O \|C- O \|C-H [ ]KOH Major ProductP

  1. Ph- O \|C-COO K
  2. Ph- OH |CH-CH2OH
  3. Ph- OH |CH-COO K
  4. Ph- O \|C-CH2OH
Ques. 11JEE Main 2025, 2 April (Morning Shift)

Given below are two statements: In the light of the above statements, choose the most appropriate answer from the options given below :

  1. Statement I is correct but Statement II is incorrect
  2. Both Statement I and Statement II are correct
  3. Both Statement I and Statement II are incorrect
  4. Statement I is incorrect but Statement II is correct

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