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JEE Advanced Previous Year Questions (2021 - 2025): Aldehydes, Ketones and Carboxylic Acids
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Page 1 Q1: An organic compound P having molecular formula C 6H 6O3 gives ferric chloride test and does not have intramolecular hydrogen bond. The compound P reacts with 3 equivalents of NH 2OH to produce oxime Q. Treatment of P with excess methyl iodide in the presence of KOH produces compound R as the major product. Reaction of R with excess iso-butylmagnesium bromide followed by treatment with H 3O? gives compound S as the major product. The total number of methyl (-CH 3) group(s) in compound S is ___. [JEE Advanced 2024 Paper 2] Ans: 2 or 6 or 12 1. The molecular formula of the organic compound P is C 6H 6O3, and it gives a ferric chloride test, which indicates the presence of a phenol functional group. 2. The fact that P does not have an intramolecular hydrogen bond suggests that it is not a compound like salicylic acid (which has an intramolecular hydrogen bond). 3. P reacts with 3 equivalents of NH 2OH (hydroxylamine) to form oxime Q, suggesting that P contains three carbonyl (C=O) groups. A possible structure that satis es this condition is 2,4,6- trihydroxybenzophenone (phloroglucinol-triketone form). 4. When P is treated with excess CH 3I in the presence of KOH, O-methylation occurs, converting hydroxyl (-OH) groups into methoxy (-OCH 3) groups. The major product R is likely 2,4,6-trimethoxybenzophenone. 5. Reaction of R with excess iso-butylmagnesium bromide (Grignard reagent) followed by acidic hydrolysis results in the addition of two iso-butyl groups to the carbonyl carbon of the benzophenone structure, yielding a tertiary alcohol. 6. The total number of methyl (-CH 3) groups in the nal compound S includes: The three -OCH 3 groups from the trimethoxybenzophenone derivative. The three -CH 3 groups present in each of the two iso-butyl groups attached to the benzophenone carbon. Thus, the total number of methyl (-CH 3) groups in compound S is: 3 from methoxy groups 3 from each of the two iso-butyl groups (total 6) T otal = 3 + 6 + 3 = 12 The possible correct answers are 2, 6, or 12. Q2: An organic compound P with molecular formula C 9H 18O2 decolorizes bromine water and also shows positive iodoform test. P on ozonolysis followed by treatment with H 2O2 gives Q and R. While compound Q shows positive iodoform test, compound R does not give positive iodoform test. Q and R on oxidation with pyridinium chlorochromate (PCC) followed by heating give S and T, respectively. Both S and T show positive iodoform test. Complete copolymerization of 500 moles of Q and 500 moles of R gives one mole of a single acyclic copolymer U. [Given, atomic mass: H = 1, C = 12, O = 16] Sum of number of oxygen atoms in S and T is ______. [JEE Advanced 2024 Paper 2] Ans: 2 Page 2 Q1: An organic compound P having molecular formula C 6H 6O3 gives ferric chloride test and does not have intramolecular hydrogen bond. The compound P reacts with 3 equivalents of NH 2OH to produce oxime Q. Treatment of P with excess methyl iodide in the presence of KOH produces compound R as the major product. Reaction of R with excess iso-butylmagnesium bromide followed by treatment with H 3O? gives compound S as the major product. The total number of methyl (-CH 3) group(s) in compound S is ___. [JEE Advanced 2024 Paper 2] Ans: 2 or 6 or 12 1. The molecular formula of the organic compound P is C 6H 6O3, and it gives a ferric chloride test, which indicates the presence of a phenol functional group. 2. The fact that P does not have an intramolecular hydrogen bond suggests that it is not a compound like salicylic acid (which has an intramolecular hydrogen bond). 3. P reacts with 3 equivalents of NH 2OH (hydroxylamine) to form oxime Q, suggesting that P contains three carbonyl (C=O) groups. A possible structure that satis es this condition is 2,4,6- trihydroxybenzophenone (phloroglucinol-triketone form). 4. When P is treated with excess CH 3I in the presence of KOH, O-methylation occurs, converting hydroxyl (-OH) groups into methoxy (-OCH 3) groups. The major product R is likely 2,4,6-trimethoxybenzophenone. 5. Reaction of R with excess iso-butylmagnesium bromide (Grignard reagent) followed by acidic hydrolysis results in the addition of two iso-butyl groups to the carbonyl carbon of the benzophenone structure, yielding a tertiary alcohol. 6. The total number of methyl (-CH 3) groups in the nal compound S includes: The three -OCH 3 groups from the trimethoxybenzophenone derivative. The three -CH 3 groups present in each of the two iso-butyl groups attached to the benzophenone carbon. Thus, the total number of methyl (-CH 3) groups in compound S is: 3 from methoxy groups 3 from each of the two iso-butyl groups (total 6) T otal = 3 + 6 + 3 = 12 The possible correct answers are 2, 6, or 12. Q2: An organic compound P with molecular formula C 9H 18O2 decolorizes bromine water and also shows positive iodoform test. P on ozonolysis followed by treatment with H 2O2 gives Q and R. While compound Q shows positive iodoform test, compound R does not give positive iodoform test. Q and R on oxidation with pyridinium chlorochromate (PCC) followed by heating give S and T, respectively. Both S and T show positive iodoform test. Complete copolymerization of 500 moles of Q and 500 moles of R gives one mole of a single acyclic copolymer U. [Given, atomic mass: H = 1, C = 12, O = 16] Sum of number of oxygen atoms in S and T is ______. [JEE Advanced 2024 Paper 2] Ans: 2 Sum of oxygen atoms in S and T = 1 + 1 = 2 Q3: An organic compound P with molecular formula C 9H 18O2 decolorizes bromine water and also shows positive iodoform test. P on ozonolysis followed by treatment with H 2O2 gives Q and R. While compound Q shows positive iodoform test, compound R does not give positive iodoform test. Q and R on oxidation with pyridinium chlorochromate (PCC) followed by heating give S and T, respectively. Both S and T show positive iodoform test. Complete copolymerization of 500 moles of Q and 500 moles of R gives one mole of a single acyclic copolymer U. [Given, atomic mass: H = 1, C = 12, O = 16] The molecular weight of U is ______. [JEE Advanced 2024 Paper 2] Ans: 93018 Molecular mass of polymers = (104 × 500) + (118 × 500) - 18 × 999 = 52000 + 59000 - 17982 = 93018 Q4: Complete reaction of acetaldehyde with excess formaldehyde, upon heating with conc. NaOH solution, gives P and Q. Compound P does not give T ollens' test, whereas Q on acidi cation gives positive T ollens' test. Treatment of P with excess cyclohexanone in the presence of catalytic amount of p-toluenesulfonic Page 3 Q1: An organic compound P having molecular formula C 6H 6O3 gives ferric chloride test and does not have intramolecular hydrogen bond. The compound P reacts with 3 equivalents of NH 2OH to produce oxime Q. Treatment of P with excess methyl iodide in the presence of KOH produces compound R as the major product. Reaction of R with excess iso-butylmagnesium bromide followed by treatment with H 3O? gives compound S as the major product. The total number of methyl (-CH 3) group(s) in compound S is ___. [JEE Advanced 2024 Paper 2] Ans: 2 or 6 or 12 1. The molecular formula of the organic compound P is C 6H 6O3, and it gives a ferric chloride test, which indicates the presence of a phenol functional group. 2. The fact that P does not have an intramolecular hydrogen bond suggests that it is not a compound like salicylic acid (which has an intramolecular hydrogen bond). 3. P reacts with 3 equivalents of NH 2OH (hydroxylamine) to form oxime Q, suggesting that P contains three carbonyl (C=O) groups. A possible structure that satis es this condition is 2,4,6- trihydroxybenzophenone (phloroglucinol-triketone form). 4. When P is treated with excess CH 3I in the presence of KOH, O-methylation occurs, converting hydroxyl (-OH) groups into methoxy (-OCH 3) groups. The major product R is likely 2,4,6-trimethoxybenzophenone. 5. Reaction of R with excess iso-butylmagnesium bromide (Grignard reagent) followed by acidic hydrolysis results in the addition of two iso-butyl groups to the carbonyl carbon of the benzophenone structure, yielding a tertiary alcohol. 6. The total number of methyl (-CH 3) groups in the nal compound S includes: The three -OCH 3 groups from the trimethoxybenzophenone derivative. The three -CH 3 groups present in each of the two iso-butyl groups attached to the benzophenone carbon. Thus, the total number of methyl (-CH 3) groups in compound S is: 3 from methoxy groups 3 from each of the two iso-butyl groups (total 6) T otal = 3 + 6 + 3 = 12 The possible correct answers are 2, 6, or 12. Q2: An organic compound P with molecular formula C 9H 18O2 decolorizes bromine water and also shows positive iodoform test. P on ozonolysis followed by treatment with H 2O2 gives Q and R. While compound Q shows positive iodoform test, compound R does not give positive iodoform test. Q and R on oxidation with pyridinium chlorochromate (PCC) followed by heating give S and T, respectively. Both S and T show positive iodoform test. Complete copolymerization of 500 moles of Q and 500 moles of R gives one mole of a single acyclic copolymer U. [Given, atomic mass: H = 1, C = 12, O = 16] Sum of number of oxygen atoms in S and T is ______. [JEE Advanced 2024 Paper 2] Ans: 2 Sum of oxygen atoms in S and T = 1 + 1 = 2 Q3: An organic compound P with molecular formula C 9H 18O2 decolorizes bromine water and also shows positive iodoform test. P on ozonolysis followed by treatment with H 2O2 gives Q and R. While compound Q shows positive iodoform test, compound R does not give positive iodoform test. Q and R on oxidation with pyridinium chlorochromate (PCC) followed by heating give S and T, respectively. Both S and T show positive iodoform test. Complete copolymerization of 500 moles of Q and 500 moles of R gives one mole of a single acyclic copolymer U. [Given, atomic mass: H = 1, C = 12, O = 16] The molecular weight of U is ______. [JEE Advanced 2024 Paper 2] Ans: 93018 Molecular mass of polymers = (104 × 500) + (118 × 500) - 18 × 999 = 52000 + 59000 - 17982 = 93018 Q4: Complete reaction of acetaldehyde with excess formaldehyde, upon heating with conc. NaOH solution, gives P and Q. Compound P does not give T ollens' test, whereas Q on acidi cation gives positive T ollens' 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 (-CH 2-) and oxygen atoms in R is ________. [JEE Advanced 2024 Paper 1] Ans: 18 Number of CH 2 groups in R = 14 Number of O-atoms = 4 Required Answer = 14 + 4 = 18 Q5: In the following reaction sequence, the major product Q is [JEE Advanced 2024 Paper 2] (a) (b) (c) (d) Ans: (d) Page 4 Q1: An organic compound P having molecular formula C 6H 6O3 gives ferric chloride test and does not have intramolecular hydrogen bond. The compound P reacts with 3 equivalents of NH 2OH to produce oxime Q. Treatment of P with excess methyl iodide in the presence of KOH produces compound R as the major product. Reaction of R with excess iso-butylmagnesium bromide followed by treatment with H 3O? gives compound S as the major product. The total number of methyl (-CH 3) group(s) in compound S is ___. [JEE Advanced 2024 Paper 2] Ans: 2 or 6 or 12 1. The molecular formula of the organic compound P is C 6H 6O3, and it gives a ferric chloride test, which indicates the presence of a phenol functional group. 2. The fact that P does not have an intramolecular hydrogen bond suggests that it is not a compound like salicylic acid (which has an intramolecular hydrogen bond). 3. P reacts with 3 equivalents of NH 2OH (hydroxylamine) to form oxime Q, suggesting that P contains three carbonyl (C=O) groups. A possible structure that satis es this condition is 2,4,6- trihydroxybenzophenone (phloroglucinol-triketone form). 4. When P is treated with excess CH 3I in the presence of KOH, O-methylation occurs, converting hydroxyl (-OH) groups into methoxy (-OCH 3) groups. The major product R is likely 2,4,6-trimethoxybenzophenone. 5. Reaction of R with excess iso-butylmagnesium bromide (Grignard reagent) followed by acidic hydrolysis results in the addition of two iso-butyl groups to the carbonyl carbon of the benzophenone structure, yielding a tertiary alcohol. 6. The total number of methyl (-CH 3) groups in the nal compound S includes: The three -OCH 3 groups from the trimethoxybenzophenone derivative. The three -CH 3 groups present in each of the two iso-butyl groups attached to the benzophenone carbon. Thus, the total number of methyl (-CH 3) groups in compound S is: 3 from methoxy groups 3 from each of the two iso-butyl groups (total 6) T otal = 3 + 6 + 3 = 12 The possible correct answers are 2, 6, or 12. Q2: An organic compound P with molecular formula C 9H 18O2 decolorizes bromine water and also shows positive iodoform test. P on ozonolysis followed by treatment with H 2O2 gives Q and R. While compound Q shows positive iodoform test, compound R does not give positive iodoform test. Q and R on oxidation with pyridinium chlorochromate (PCC) followed by heating give S and T, respectively. Both S and T show positive iodoform test. Complete copolymerization of 500 moles of Q and 500 moles of R gives one mole of a single acyclic copolymer U. [Given, atomic mass: H = 1, C = 12, O = 16] Sum of number of oxygen atoms in S and T is ______. [JEE Advanced 2024 Paper 2] Ans: 2 Sum of oxygen atoms in S and T = 1 + 1 = 2 Q3: An organic compound P with molecular formula C 9H 18O2 decolorizes bromine water and also shows positive iodoform test. P on ozonolysis followed by treatment with H 2O2 gives Q and R. While compound Q shows positive iodoform test, compound R does not give positive iodoform test. Q and R on oxidation with pyridinium chlorochromate (PCC) followed by heating give S and T, respectively. Both S and T show positive iodoform test. Complete copolymerization of 500 moles of Q and 500 moles of R gives one mole of a single acyclic copolymer U. [Given, atomic mass: H = 1, C = 12, O = 16] The molecular weight of U is ______. [JEE Advanced 2024 Paper 2] Ans: 93018 Molecular mass of polymers = (104 × 500) + (118 × 500) - 18 × 999 = 52000 + 59000 - 17982 = 93018 Q4: Complete reaction of acetaldehyde with excess formaldehyde, upon heating with conc. NaOH solution, gives P and Q. Compound P does not give T ollens' test, whereas Q on acidi cation gives positive T ollens' 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 (-CH 2-) and oxygen atoms in R is ________. [JEE Advanced 2024 Paper 1] Ans: 18 Number of CH 2 groups in R = 14 Number of O-atoms = 4 Required Answer = 14 + 4 = 18 Q5: In the following reaction sequence, the major product Q is [JEE Advanced 2024 Paper 2] (a) (b) (c) (d) Ans: (d) Q6: The major products obtained from the reactions in List-II are the reactants for the named reactions mentioned in List-I. Match List-I with List-II and choose the correct option. [JEE Advanced 2024 Paper 1] Page 5 Q1: An organic compound P having molecular formula C 6H 6O3 gives ferric chloride test and does not have intramolecular hydrogen bond. The compound P reacts with 3 equivalents of NH 2OH to produce oxime Q. Treatment of P with excess methyl iodide in the presence of KOH produces compound R as the major product. Reaction of R with excess iso-butylmagnesium bromide followed by treatment with H 3O? gives compound S as the major product. The total number of methyl (-CH 3) group(s) in compound S is ___. [JEE Advanced 2024 Paper 2] Ans: 2 or 6 or 12 1. The molecular formula of the organic compound P is C 6H 6O3, and it gives a ferric chloride test, which indicates the presence of a phenol functional group. 2. The fact that P does not have an intramolecular hydrogen bond suggests that it is not a compound like salicylic acid (which has an intramolecular hydrogen bond). 3. P reacts with 3 equivalents of NH 2OH (hydroxylamine) to form oxime Q, suggesting that P contains three carbonyl (C=O) groups. A possible structure that satis es this condition is 2,4,6- trihydroxybenzophenone (phloroglucinol-triketone form). 4. When P is treated with excess CH 3I in the presence of KOH, O-methylation occurs, converting hydroxyl (-OH) groups into methoxy (-OCH 3) groups. The major product R is likely 2,4,6-trimethoxybenzophenone. 5. Reaction of R with excess iso-butylmagnesium bromide (Grignard reagent) followed by acidic hydrolysis results in the addition of two iso-butyl groups to the carbonyl carbon of the benzophenone structure, yielding a tertiary alcohol. 6. The total number of methyl (-CH 3) groups in the nal compound S includes: The three -OCH 3 groups from the trimethoxybenzophenone derivative. The three -CH 3 groups present in each of the two iso-butyl groups attached to the benzophenone carbon. Thus, the total number of methyl (-CH 3) groups in compound S is: 3 from methoxy groups 3 from each of the two iso-butyl groups (total 6) T otal = 3 + 6 + 3 = 12 The possible correct answers are 2, 6, or 12. Q2: An organic compound P with molecular formula C 9H 18O2 decolorizes bromine water and also shows positive iodoform test. P on ozonolysis followed by treatment with H 2O2 gives Q and R. While compound Q shows positive iodoform test, compound R does not give positive iodoform test. Q and R on oxidation with pyridinium chlorochromate (PCC) followed by heating give S and T, respectively. Both S and T show positive iodoform test. Complete copolymerization of 500 moles of Q and 500 moles of R gives one mole of a single acyclic copolymer U. [Given, atomic mass: H = 1, C = 12, O = 16] Sum of number of oxygen atoms in S and T is ______. [JEE Advanced 2024 Paper 2] Ans: 2 Sum of oxygen atoms in S and T = 1 + 1 = 2 Q3: An organic compound P with molecular formula C 9H 18O2 decolorizes bromine water and also shows positive iodoform test. P on ozonolysis followed by treatment with H 2O2 gives Q and R. While compound Q shows positive iodoform test, compound R does not give positive iodoform test. Q and R on oxidation with pyridinium chlorochromate (PCC) followed by heating give S and T, respectively. Both S and T show positive iodoform test. Complete copolymerization of 500 moles of Q and 500 moles of R gives one mole of a single acyclic copolymer U. [Given, atomic mass: H = 1, C = 12, O = 16] The molecular weight of U is ______. [JEE Advanced 2024 Paper 2] Ans: 93018 Molecular mass of polymers = (104 × 500) + (118 × 500) - 18 × 999 = 52000 + 59000 - 17982 = 93018 Q4: Complete reaction of acetaldehyde with excess formaldehyde, upon heating with conc. NaOH solution, gives P and Q. Compound P does not give T ollens' test, whereas Q on acidi cation gives positive T ollens' 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 (-CH 2-) and oxygen atoms in R is ________. [JEE Advanced 2024 Paper 1] Ans: 18 Number of CH 2 groups in R = 14 Number of O-atoms = 4 Required Answer = 14 + 4 = 18 Q5: In the following reaction sequence, the major product Q is [JEE Advanced 2024 Paper 2] (a) (b) (c) (d) Ans: (d) Q6: The major products obtained from the reactions in List-II are the reactants for the named reactions mentioned in List-I. Match List-I with List-II and choose the correct option. [JEE Advanced 2024 Paper 1] (a) P-3, Q-5, R-4, S-1 (b) P-3, Q-2, R-4, S-1 (c) P-3, Q-5, R-1, S-4 (d) P-5, Q-2, R-4, S-1 Ans: (a)Read More
FAQs on JEE Advanced Previous Year Questions (2021 - 2025): Aldehydes, Ketones and Carboxylic Acids
| 1. What are the general methods for the synthesis of aldehydes and ketones? |  |
Ans. Aldehydes can be synthesized through methods like the oxidation of primary alcohols, the reduction of esters, and the hydrolysis of alkyl halides. Ketones can be produced by the oxidation of secondary alcohols, Friedel-Crafts acylation, and the reaction of acid chlorides with organolithium reagents.
| 2. How do the physical properties of aldehydes and ketones differ from those of alcohols? | |
Ans. Aldehydes and ketones generally have lower boiling points compared to alcohols of similar molecular weight due to the absence of hydrogen bonding. However, they exhibit dipole-dipole interactions due to the carbonyl group, which contributes to their solubility in polar solvents.
| 3. What is the significance of the reagent Grignard in the synthesis of aldehydes and ketones? | |
Ans. Grignard reagents (organomagnesium halides) are crucial for synthesizing aldehydes and ketones as they react with carbonyl compounds. For example, reacting a Grignard reagent with formaldehyde yields a primary alcohol (aldehyde), while reacting it with other aldehydes or ketones results in secondary or tertiary alcohols, respectively.
| 4. What are some common reactions involving carboxylic acids, and how do they differ from those of aldehydes and ketones? | |
Ans. Carboxylic acids can undergo reactions such as acid-base reactions (forming salts), esterification (forming esters), and decarboxylation. Unlike aldehydes and ketones, carboxylic acids can donate protons due to their acidic nature, which makes them more reactive in certain types of reactions compared to aldehydes and ketones.
| 5. How can one distinguish between aldehydes and ketones using chemical tests? | |
Ans. Aldehydes can be distinguished from ketones using tests such as the Tollens' test (which produces a silver mirror with aldehydes) or the Fehling's test (which reduces to a brick-red precipitate with aldehydes). Ketones do not give these reactions, making these tests useful for differentiation.
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