Aldehydes, Ketones and Carboxylic Acids is the most-asked Organic chapter in NEET. It has more named reactions than any other chapter, and NTA uses them every year. This aldehydes ketones NEET PYQ analysis shows which reactions, tests and orders repeat, so you can turn a long chapter into a reliable set of marks.
For how this chapter fits the wider Organic plan, see our organic mechanisms preparation guide. This article focuses on what past papers actually ask.
Want to test yourself first? Solve the Aldehydes, Ketones and Carboxylic Acids PYQs for free, then use this guide to fix the gaps.
Table of Contents
Why This Chapter Matters Most in Organic
NEET usually asks two to three questions from this chapter, more than any other Organic chapter. It is also where reaction-sequence questions (“identify A, B and C”) are most common.
Alcohols are both the starting point and the product of many reactions here, so revise our Alcohols and Phenols PYQ patterns article alongside. Keep the Aldehydes and Ketones class notes and our named reagents revision list open as you read. See the chapter’s share in the NEET 2027 chapter weightage breakdown.
Aldehydes Ketones NEET PYQ Analysis: The Repeated Question Types
When you sort a decade of NEET chemistry PYQs from this chapter, five question types cover almost everything.
| Question type | Frequency | What it tests |
|---|---|---|
| Named reactions | Most frequent | Aldol, Cannizzaro, Clemmensen, Wolff–Kishner, HVZ |
| Nucleophilic addition | Very frequent | Reactivity order, HCN, NaHSO₃, Grignard |
| Distinguishing tests | Very frequent | Tollens’, Fehling’s, iodoform |
| Preparation | Regular | Rosenmund, Stephen, Etard, Gattermann–Koch |
| Acidity of carboxylic acids | Regular | Effect of substituents |
Nucleophilic Addition: Reactivity Order
Reactivity: HCHO > CH₃CHO > CH₃COCH₃ > aromatic ketones.
Two reasons explain it:
- Electronic: alkyl groups push electrons onto the carbonyl carbon, making it less positive.
- Steric: bulky groups around the carbonyl block the nucleophile.
Aromatic aldehydes and ketones are less reactive than aliphatic ones, because the benzene ring donates electron density by resonance.
Common addition reactions: HCN (cyanohydrin), NaHSO₃ (bisulphite adduct), Grignard reagents (alcohols) and ammonia derivatives (oximes, hydrazones, semicarbazones, 2,4-DNP derivatives).
Named Reactions That Repeat
| Reaction | What happens |
|---|---|
| Aldol condensation | Aldehydes or ketones with an α-hydrogen + dilute alkali give a β-hydroxy carbonyl, which loses water on heating |
| Cannizzaro reaction | Aldehydes without an α-hydrogen (HCHO, C₆H₅CHO) + conc. alkali give an alcohol and a carboxylate salt |
| Clemmensen reduction | Zn–Hg + conc. HCl reduces C=O to CH₂ |
| Wolff–Kishner reduction | NH₂NH₂, then KOH in ethylene glycol, reduces C=O to CH₂ |
| Rosenmund reduction | Acid chloride + H₂ over Pd–BaSO₄ gives an aldehyde |
| Stephen reaction | Nitrile + SnCl₂/HCl, then hydrolysis, gives an aldehyde |
| Etard reaction | Toluene + CrO₂Cl₂ gives benzaldehyde |
| HVZ reaction | Carboxylic acid with an α-hydrogen + X₂/red P gives an α-halo acid |
The key decision in many questions is aldol condensation versus Cannizzaro reaction: check for an α-hydrogen. If it is present, aldol; if it is absent, Cannizzaro with concentrated alkali. In a crossed version with HCHO, formaldehyde is always oxidised to formate.
Distinguishing Tests
| Test | Positive for | Result |
|---|---|---|
| Tollens’ reagent | All aldehydes, including aromatic | Silver mirror |
| Fehling’s solution | Aliphatic aldehydes only | Red-brown precipitate of Cu₂O |
| Iodoform test | CH₃CO– group or CH₃CH(OH)– group | Yellow precipitate of CHI₃ |
Ketones do not respond to Tollens’ or Fehling’s reagent. Benzaldehyde gives Tollens’ test but not Fehling’s. Ethanol and acetaldehyde give the iodoform test; methanol and formaldehyde do not. Formic acid also gives Tollens’ test, because it has an aldehyde-like H–C=O group.
Carboxylic Acids: Acidity
- Electron-withdrawing groups increase acidity; electron-donating groups decrease it.
- Order: CF₃COOH > CCl₃COOH > CHCl₂COOH > ClCH₂COOH > HCOOH > CH₃COOH.
- Benzoic acid is more acidic than acetic acid; nitro groups on the ring make it stronger still.
Worked PYQ-Pattern Questions
Q1. Which of these disproportionates in concentrated NaOH? (a) CH₃CHO (b) CH₃COCH₃ (c) C₆H₅CHO (d) CH₃CH₂CHO
Answer: (c) Benzaldehyde. It has no α-hydrogen.
Q2. Which is most reactive towards nucleophilic addition? (a) HCHO (b) CH₃CHO (c) CH₃COCH₃ (d) C₆H₅COCH₃
Answer: (a) HCHO. It has no electron-donating groups and the least crowding.
Q3. Which reagent converts a ketone to an alkane in basic conditions?
Answer: Hydrazine followed by KOH in ethylene glycol (Wolff–Kishner reduction).
Q4. Which compound gives a positive iodoform test? (a) Methanol (b) Propan-1-ol (c) Ethanol (d) Benzaldehyde
Answer: (c) Ethanol. It has the CH₃CH(OH)– group.
Q5. Which aldehyde does not give Fehling’s test?
Answer: Benzaldehyde. Aromatic aldehydes do not reduce Fehling’s solution.
Common Traps in This Chapter
- Expecting an aldol product from an aldehyde without an α-hydrogen
- Saying aromatic aldehydes give Fehling’s test
- Mixing up Clemmensen (acidic) and Wolff–Kishner (basic) conditions
- Forgetting that ethanol gives the iodoform test
- Ranking CH₃COOH above HCOOH in acidity (HCOOH is the stronger acid)
Practise Every Aldehydes and Ketones PYQ
This aldehydes ketones NEET PYQ analysis gives you the reactions, tests and orders. Practice makes them automatic. Every previous year question from this chapter is available chapter-wise, free:
👉 Solve all Aldehydes, Ketones and Carboxylic Acids NEET PYQs
For every “identify A, B, C” question, write the reagent’s job (oxidise, reduce, add, condense) above each arrow before naming the products.
Conclusion
This is the heaviest Organic chapter, but it is also the most predictable. Use this aldehydes ketones NEET PYQ analysis to master the reactivity order, the named reactions, the three distinguishing tests and acidity orders. Then practise until every reagent tells you the product at a glance.
FAQ
Q: How many questions come from Aldehydes, Ketones and Carboxylic Acids in NEET? A: Usually two to three questions, which makes it the most important Organic chapter.
Q: What is the difference between aldol condensation and the Cannizzaro reaction? A: The aldol route needs an α-hydrogen and dilute alkali. Cannizzaro works with aldehydes that have no α-hydrogen, in concentrated alkali.
Q: Which aldehydes give Fehling’s test? A: Aliphatic aldehydes. Aromatic aldehydes such as benzaldehyde and all ketones do not.
Q: Which compounds give the iodoform test? A: Compounds with a CH₃CO– group, such as acetone and acetaldehyde, or a CH₃CH(OH)– group, such as ethanol and propan-2-ol.
Q: How should I revise this chapter for NEET? A: Use an aldehydes ketones NEET PYQ analysis to list the repeated reactions, make one named-reaction table, and solve past questions chapter-wise.
Q: Where can I practise these PYQs for free? A: You can solve every previous year question from this chapter for free using the practice link in this article.