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Aldehydes, Ketones and Carboxylic Acids · Question 26

JEE Main 2025 (Online) 8th April Evening ShiftMCQMedium📈 Topic in 32% papers+4−1
1

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

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]

Answer

(2) [figure]

Solution

The compound is 6-oxoheptanal: CH3-CO-CH2-CH2-CH2-CH2-CHO (C-1 = CHO carbon, C-6 = keto carbon).

Possible intramolecular aldol reactions:

(a) Enolate at C-5 (α to the ketone) attacks the CHO carbon (C-1) five-membered ring; dehydration gives 1-acetylcyclopentene [structure (2)].

(b) Enolate at C-2 (α to CHO) attacks the keto carbon (C-6) five-membered ring; dehydration gives 2-methylcyclopent-1-ene-1-carbaldehyde [structure (3)].

(c) Enolate of the CH3 group (C-7) attacks the CHO carbon strained seven-membered ring [structure (4)] — not favoured.

The aldehyde carbonyl is more electrophilic (less hindered, only one electron-releasing group) than the keto carbonyl, path (a) is preferred, and a five-membered ring forms easily.

After dehydration the C=C is conjugated with C=O (α,β-unsaturated ketone).

Major product: 1-acetylcyclopentene (1-(cyclopent-1-en-1-yl)ethan-1-one).

Answer: (2)

JEE Main 2025 (Online) 8th April Evening Shift

Keep practising — Aldehydes, Ketones and Carboxylic Acids

2

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
3

"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
4

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
5

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
6

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
JEE Main 2025 (Online) 3rd April Morning Shift
7

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
JEE Main 2025 (Online) 3rd April Evening Shift
8

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
JEE Main 2025 (Online) 2nd April Morning Shift
9

Consider the following molecules: [figure] The correct order of rate of hydrolysis is :

  1. p > q > r > s
  2. r > q > p > s
  3. p > r > q > s
  4. q > p > r > s
JEE Main 2025 (Online) 2nd April Morning Shift
10

Consider the following reactions. From these reactions which reaction will give carboxylic acid as a major product? Choose the correct answer from the options given below:

  1. A, B and E only
  2. A and D only
  3. B, C and E only
  4. B and E only
JEE Main 2025 (Online) 2nd April Evening Shift
11

The product (P) formed in the following reaction is : [figure]

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
JEE Main 2025 (Online) 29th January Morning Shift

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