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Aldehydes, Ketones and Carboxylic Acids · Question 9

JEE Advanced 2025 Paper 2MCQHard📈 Topic in 17% papers+4−1
1

Monocyclic compounds P, Q, R and S are the major products formed in the reaction sequences given below. [figure] The product having the highest number of unsaturated carbon atom(s) is

  1. P
  2. Q
  3. R
  4. S

Answer

(4) S

Solution

Unsaturated (sp2 / sp) carbons are counted in each product.

P (HVZ reaction – -bromination of the acid):

[figure] [(ii) H2O](i) Br2/Red P [figure] (P)

Unsaturated C = 6 (ring) + 1 (COOH) = 7

Q (cross aldol, then dehydration – Claisen–Schmidt):

[figure] + [figure] aq. NaOH, 293 K [figure] (Q)

Unsaturated C = 6 + 2 + 1 = 9

R (terminal alkyne → acetylide; SN2 on allyl bromide; then Hg2+ hydration of the C≡C):

[figure] NaNH2 [figure] CH2=CH-CH2Br [figure]

Hg2+, H3O+ [figure] (R)

Unsaturated C = 6 + 1 (C=O) + 2 (C=C) = 9

S (ozonolysis opens the five-membered ring to a keto-aldehyde; both C=O groups take one CH3MgBr; acid/heat dehydrates both alcohols):

[figure] O3, Zn-H2O [figure]

CH3MgBr (2 equiv.), then H2O [figure]

H+, (-2H2O) [figure] (S)

Unsaturated C = 6 + 2 + 2 = 10

S has the highest number (10) of unsaturated carbon atoms.

Answer: (D)

JEE Advanced 2025 Paper 2

Keep practising — Aldehydes, Ketones and Carboxylic Acids

2

Reaction of iso-propylbenzene with O2 followed by the treatment with H3O+ forms phenol and a by-product P. Reaction of P with 3 equivalents of Cl2 gives compound Q. Treatment of Q with Ca(OH)2 produces compound R and calcium salt S. The correct statement(s) regarding P, Q, R and S is(are)

  1. Reaction of P with R in the presence of KOH followed by acidification gives [figure]
  2. Reaction of R with O2 in the presence of light gives phosgene gas
  3. Q reacts with aqueous NaOH to produce Cl3CCH2OH and Cl3CCOONa
  4. S on heating gives P
JEE Advanced 2024 Paper 1
3

Complete reaction of acetaldehyde with excess formaldehyde, upon heating with conc. NaOH solution, gives P and Q. Compound P does not give Tollens’ test, whereas Q on acidification gives positive Tollens’ test. Treatment of P with excess cyclohexanone in the presence of catalytic amount of p-toluenesulfonic acid (PTSA) gives product R. Sum of the number of methylene groups (-CH2-) and oxygen atoms in R is .

JEE Advanced 2024 Paper 1
4

List-I contains various reaction sequences and List-II contains the possible products. Match each entry in List-I with the appropriate entry in List-II and choose the correct option.

  1. P-3, Q-5, R-4, S-1
  2. P-3, Q-2, R-4, S-1
  3. P-3, Q-5, R-1, S-4
  4. P-5, Q-2, R-4, S-1
JEE Advanced 2024 Paper 1
5

In the following reaction sequence, the major product P is formed. [figure] Glycerol reacts completely with excess P in the presence of an acid catalyst to form Q. Reaction of Q with excess NaOH followed by the treatment with CaCl2 yields Ca-soap R, quantitatively. Starting with one mole of Q, the amount of R produced in gram is . [Given, atomic weight: H = 1, C = 12, N = 14, O = 16, Na = 23, Cl = 35, Ca = 40]

JEE Advanced 2024 Paper 1
6

The option(s) with correct sequence of reagents for the conversion of P to Q is(are) [figure]

  1. i) Lindlar’s catalyst, H2; ii) SnCl2/HCl; iii) NaBH4; iv) H3O+
  2. i) Lindlar’s catalyst, H2; ii) H3O+; iii) SnCl2/HCl; iv) NaBH4
  3. i) NaBH4; ii) SnCl2/HCl; iii) H3O+; iv) Lindlar’s catalyst, H2
  4. i) Lindlar’s catalyst, H2; ii) NaBH4; iii) SnCl2/HCl; iv) H3O+
JEE Advanced 2024 Paper 2
7

Sum of number of oxygen atoms in S and T is .

JEE Advanced 2024 Paper 2

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