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Aldehydes, Ketones and Carboxylic Acids · Question 4

JEE Main 2026 (Online) 5th April Morning ShiftMCQHard📈 Topic in 32% papers+4−1
1

" P " is a hydrocarbon of molecular formula:- C8H14. On ozonolysis, " P " forms "Q". "Q" on treatment with alkali under reflux condition produces "R", which on treatment with I2/NaOH gives a yellow precipitate. Acidification of the solution gives "S". The structure of "S" is given below:- [figure] The correct structure of P is

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

Answer

(4) [figure]

Solution

Work backwards from S:

• S is an α,β-unsaturated acid formed by the haloform reaction (yellow ppt of CHI3) ⇒ R is the methyl ketone with –COCH3 in place of –COOH (1-acetyl-2-methylcyclopentene).

• R is formed from Q by alkali under reflux ⇒ intramolecular aldol condensation of a diketone ⇒ Q = octane-2,7-dione, CH3CO(CH2)4COCH3 (the α-CH2 next to one C=O attacks the other C=O and forms a five-membered ring).

• Q (8 C, both C=O in one chain) comes from ozonolysis of a cyclic alkene in which both doubly bonded C carry a CH3 ⇒ P = 1,2-dimethylcyclohexene ( C8H14 ✓).

[figure]

[figure]

(Options 1 and 3 give a dialdehyde / different chain on ozonolysis; option 2 gives a keto-aldehyde that cannot lead to S.)

Answer: (4)

JEE Main 2026 (Online) 5th April Morning Shift

Keep practising — Aldehydes, Ketones and Carboxylic Acids

2

Complete the following reaction sequence and give the name of major product 'P'. [figure]

  1. 2-Chloropropanoic acid
  2. 3-Chloropropanoic acid
  3. 1-Chloropropane
  4. 2-Chloropropane
JEE Main 2026 (Online) 5th April Evening Shift
3

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

  1. Both Statement I and Statement II are true
  2. Both Statement I and Statement II are false
  3. Statement I is true but Statement II is false
  4. Statement I is false but Statement II is true
JEE Main 2026 (Online) 5th April Evening Shift
4

Consider the following sequence of reactions to give the major product (X) [figure] P g of the major product (X) formed is reacted with NaHCO3 solution to liberate a gas which occupied 11.2 dm3 at STP. P = g. (Given molar mass in g mol-1 H : 1, C : 12, O : 16, Cl : 35.5)

JEE Main 2026 (Online) 4th April Morning Shift
5

An organic compound “x” where molar ratio of C, O and H are equal, on treatment with 50% KOH under reflux followed by acidification produced “y”. The most likely structure of “y” is: [Molar mass of ‘x’ is 58 g mol-1]

  1. [figure]
  2. CH3-CH=CH-CH=O
  3. [figure]
  4. [figure]
JEE Main 2026 (Online) 2nd April Evening Shift
6

A molecule (X) with following structure under mild acidic condition is hydrolysed to produce (Y) and (Z). Identify the correct statements about (Y) and (Z). [figure] Choose the correct answer from the options given below :

  1. A, B and C Only
  2. B and C Only
  3. C and D Only
  4. A and D Only
JEE Main 2026 (Online) 2nd April Evening Shift
7

Given below are the four isomeric compounds (P, Q, R, S) [figure] Identify correct statements from below. Choose the correct option.

  1. C and E only
  2. A and E only
  3. A, B, D and E only
  4. A, C and E only
JEE Main 2026 (Online) 28th January Morning Shift
8

The correct order of acidic strength of the major products formed in the given reactions, is : Choose the correct answer from the options given below :

  1. C > A > D > B
  2. A > D > C > B
  3. A > D > B > C
  4. C > B > A > D
JEE Main 2026 (Online) 28th January Evening Shift
9

A student is given one compound among the following compounds that gives positive test with Tollens' reagent. [figure] The compound is :

  1. B
  2. D
  3. A
  4. C
JEE Main 2026 (Online) 24th January Morning Shift
10

The unsaturated ether on acidic hydrolysis produces carbonyl compounds as shown below :- [figure] Based on this, predict the solution/reagent that will help to distinguish "P" and "Q" obtained in the following reaction :- CH3-CH=CH-O- CH3 |C=CH2 [ ]H3O P + Q

  1. Saturated NaHSO3 solution
  2. Fehling solution
  3. Lucas reagent
  4. 2,4-DNP reagent
JEE Main 2026 (Online) 24th January Evening Shift
11

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

  1. Statement I is true but Statement II is false
  2. Both Statement I and Statement II are false
  3. Both Statement I and Statement II are true
  4. Statement I is false but Statement II is true
JEE Main 2026 (Online) 24th January Evening Shift

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