Aldehydes, Ketones and Carboxylic AcidsNEET MCQs with solutions
Aldehydes, Ketones and Carboxylic Acids is one of NEET's heaviest Organic Chemistry chapters. Nucleophilic addition, aldol condensation, Cannizzaro reaction, Tollens' and Fehling's tests, Hell-Volhard-Zelinsky reaction and acidity of carboxylic acids are all tested. Name reactions and distinguishing tests dominate NEET questions.
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Tap an option to check it. Questions from every NCERT topic in this chapter, from easy to hard.
Q1Important PYQ Mixed Concepts
Benzoic acid is prepared from a Grignard reagent by reaction with CO2 followed by acidic hydrolysis. Which Grignard reagent is required?
Not quite — the answer is D.
The aryl Grignard reagent C6H5MgBr reacts with CO2 to give the carboxylate salt, which on acidic hydrolysis yields benzoic acid. Chlorobenzene is the precursor to the Grignard, not the Grignard itself. Phenylmagnesium chloride is less common and not the standard reagent; phenylmagnesium bromide is the correct choice.
Q2Grand Test
The correct decreasing order of acidity of HCOOH, CH3COOH, (CH3)2CHCOOH and (CH3)3CCOOH is:
Not quite — the answer is A.
Alkyl groups exert a +I inductive effect that destabilises the carboxylate ion and decreases acidity. Formic acid (HCOOH) has no alkyl group and is most acidic. Increasing alkyl substitution progressively decreases acidity, giving the order HCOOH > CH3COOH > (CH3)2CHCOOH > (CH3)3CCOOH.
Q3Mixed Revision
Which reagent is used for the selective reduction of an acid chloride to an aldehyde stopping before alcohol stage?
Not quite — the answer is B.
Rosenmund reduction uses hydrogen gas over palladium poisoned with barium sulphate, which stops the reduction at the aldehyde stage and prevents further reduction to the alcohol. LiAlH4 over-reduces to the alcohol. NaBH4 does not reduce acid chlorides under standard conditions.
Q4Structure and Nomenclature
The general formula of ketones is
Not quite — the answer is B.
Ketones have a carbonyl group bonded to two carbon groups (R and R'), distinguishing them from aldehydes where carbonyl is terminal. R-CHO is the aldehyde formula.
Q5Named Reactions
Which named reaction involves formation of a beta-hydroxy aldehyde from aldehydes having alpha hydrogen in the presence of dilute base?
Not quite — the answer is A.
Aldehydes with alpha hydrogen form an enolate in dilute base, which attacks another carbonyl to yield a beta-hydroxy aldehyde — the hallmark product of aldol condensation. Cannizzaro requires absence of alpha hydrogen. Clemmensen and HVZ involve entirely different reagents and substrates.
Q6Carboxylic Acid Derivatives
Which derivative synthesises an amide most efficiently?
Not quite — the answer is C.
Acid chloride reacts with amines under mild conditions in high yield — the excellent Cl⁻ leaving group drives the reaction. Direct reaction of carboxylic acid with amine requires very high temperature and gives poor yield due to salt formation.
Q7Reaction Mechanism
What is the first step in base-catalysed aldol condensation?
Not quite — the answer is B.
Base (OH⁻) abstracts the alpha hydrogen forming a resonance-stabilised enolate ion, which then acts as the nucleophile. Protonation of carbonyl oxygen occurs in acid catalysis, not base catalysis.
Q8Carbonyl Derivatives
Which reagent converts aldehydes and ketones into oxime derivatives?
Not quite — the answer is A.
Hydroxylamine (NH₂OH) attacks the electrophilic carbonyl carbon in a nucleophilic addition, followed by elimination of water to form the C=N–OH (oxime) linkage. Hydrazine gives hydrazone; semicarbazide gives semicarbazone.
Q9Preparation of Carboxylic Acids
Which reagent oxidises primary alcohols to carboxylic acids under reflux via the aldehyde intermediate?
Not quite — the answer is A.
KMnO₄ is a strong oxidant that takes primary alcohols through the aldehyde stage and continues to carboxylic acid. PCC stops at the aldehyde — it cannot achieve further oxidation.
Q10Chemical Reactions of Aldehydes and Ketones
Which type of reaction is most characteristic of aldehydes and ketones due to the electrophilic nature of carbonyl carbon?
Not quite — the answer is A.
The carbonyl carbon bears a partial positive charge (δ+) due to the polar C=O bond, making it susceptible to nucleophilic attack. Electrophilic substitution (Option B) is the trap — it occurs in aromatic rings, not at carbonyl carbons.
Q11Preparation of Aldehydes and Ketones
Which reagent converts primary alcohols to aldehydes without further oxidation to carboxylic acid?
Not quite — the answer is A.
PCC is a mild oxidising agent that selectively stops oxidation at the aldehyde stage. Jones reagent and K₂Cr₂O₇/H₂SO₄ over-oxidise primary alcohols to carboxylic acids.
Q12Physical Properties
Which compound among the following has the highest boiling point due to strong intermolecular hydrogen bonding and dimer formation?
Not quite — the answer is A.
Carboxylic acids form stable cyclic dimers through two O-H...O hydrogen bonds per dimer, effectively doubling intermolecular attraction. Ethanal and propanone lack O-H so cannot self-associate. Diethyl ether has no H-bond donor, making it a stronger trap than ethanol for this concept.
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Get RankUp on Google PlayQ13Chemical Reactions of Carboxylic Acids
Which type of reaction occurs when the -OH of a carboxylic acid is replaced by a nucleophile?
Not quite — the answer is A.
The carbonyl carbon of COOH is attacked by a nucleophile after protonation; the -OH leaves as a leaving group — this is nucleophilic acyl substitution. Nucleophilic addition (Option C) is the distractor — it applies to aldehydes/ketones where no leaving group departs.
Q14Distinguishing Tests and Identification
Which reagent gives a silver mirror deposit when treated with an aldehyde but shows no reaction with ketones?
Not quite — the answer is A.
Tollens' reagent (ammoniacal AgNO3) is reduced by aldehydes: the aldehyde is oxidised to a carboxylate while Ag+ is reduced to metallic silver deposited as a mirror. Ketones lack the aldehyde hydrogen and cannot reduce Tollens' reagent. Fehling's also distinguishes aldehydes from ketones but gives a precipitate, not a mirror.
Q15Reaction Mechanism and Reactivity
During nucleophilic addition to a carbonyl group, the hybridisation of the carbonyl carbon changes from which to which?
Not quite — the answer is A.
Nucleophilic attack on the planar sp2 carbonyl carbon converts it into a tetrahedral sp3 carbon as the nucleophile forms a new sigma bond using the pi electrons. The carbonyl carbon goes from three groups (trigonal planar, 120°) to four groups (tetrahedral, ~109.5°). This geometry change is the defining structural feature of the nucleophilic addition mechanism.
Q16PYQ Final
Which compound undergoes Cannizzaro reaction?
Not quite — the answer is B.
Benzaldehyde has no alpha hydrogen so enolate formation is impossible. It undergoes Cannizzaro disproportionation instead of aldol condensation. All other options have alpha hydrogen and undergo aldol condensation preferentially.
Q17Revision Master
Which compound forms hydrogen-bonded dimers giving it the strongest intermolecular association?
Not quite — the answer is C.
Carboxylic acids form cyclic dimers via two O–H···O hydrogen bonds per molecule pair — effectively doubling molecular mass in solution. Aldehydes and ketones have no O–H so cannot hydrogen bond as donors. Esters have no O–H donor.
Q18Acidity of Carboxylic Acids
Which factor is primarily responsible for the acidic nature of carboxylic acids?
Not quite — the answer is A.
After deprotonation, the carboxylate ion is stabilised by two equivalent resonance structures that distribute the negative charge equally over both oxygen atoms. Hydrogen bonding (Option B) affects physical properties but does not explain ionisation tendency.
Q19Acidity and Comparative Reactivity
Which compound is most acidic among the following?
Not quite — the answer is A.
Formic acid has no alkyl group, so its conjugate base (formate ion) is maximally stable — no electron donation destabilises it. Acetic acid and larger acids have increasing electron-donating alkyl groups that reduce acidity progressively.
Q20Structure and Nomenclature
The IUPAC name of CH₃CHO is
Not quite — the answer is C.
CH₃CHO has two carbons; aldehydes use the suffix -al, giving ethanal. Methanal is HCHO; ethanone is not a valid simple name (ketones need a locant).
Q21Structure and Nomenclature
The IUPAC name of CH₃COCH₃ is
Not quite — the answer is D.
CH₃COCH₃ has three carbons with internal carbonyl; ketone suffix is -one, giving propanone. No locant needed as only one possible position exists.
Q22Structure and Nomenclature
Which compound contains the carboxyl group?
Not quite — the answer is A.
The carboxyl group (–COOH) is present only in carboxylic acids. CH₃CHO has a formyl group; CH₃COCH₃ has a ketonic carbonyl; C₂H₅OH has a hydroxyl group.
Q23Structure and Nomenclature
The common name of HCHO is
Not quite — the answer is B.
HCHO (methanal) is commonly called formaldehyde, derived from formic acid. Acetaldehyde is CH₃CHO; propionaldehyde is CH₃CH₂CHO.
Q24Structure and Nomenclature
The common name of CH₃COCH₃ is
Not quite — the answer is C.
CH₃COCH₃ (propanone) is universally called acetone. Acetaldehyde is CH₃CHO; benzaldehyde is C₆H₅CHO.
ELITE question · AIR under 50 level
This chapter has 300 ELITE questions for students aiming at the very top. They are only in the app.
Unlock ELITE questions in the appKey Name Reactions & Tests
Quick revision: most questions in this chapter test these facts.
| Reaction / Test | Key Fact |
|---|---|
| Aldol condensation | Aldehyde with α-H + dilute NaOH → β-hydroxy aldehyde → dehydration → α,β-unsaturated aldehyde |
| Cannizzaro reaction | Aldehyde without α-H + conc. NaOH → one molecule oxidised + one reduced |
| Tollens' test | RCHO + Ag(NH₃)₂⁺ → silver mirror; aldehydes positive, ketones negative |
| Fehling's test | RCHO + Cu²⁺ → red Cu₂O precipitate; aliphatic aldehydes positive |
| Clemmensen reduction | C=O → CH₂ using Zn-Hg/HCl (acidic); Wolff-Kishner uses NH₂NH₂/KOH (basic) |
| Carboxylic acid acidity | Electron-withdrawing groups increase acidity; order: HCOOH is strongest simple acid |
What the app covers in this chapter
665 questions in total, each with a detailed explanation.
| Important PYQ Mixed Concepts | 99 |
| Grand Test | 80 |
| Mixed Revision | 58 |
| Structure and Nomenclature | 44 |
| Named Reactions | 41 |
| Carboxylic Acid Derivatives | 40 |
| Reaction Mechanism | 40 |
| Carbonyl Derivatives | 39 |
| Preparation of Carboxylic Acids | 22 |
| Chemical Reactions of Aldehydes and Ketones | 22 |
| Preparation of Aldehydes and Ketones | 21 |
| Physical Properties | 21 |
| Chemical Reactions of Carboxylic Acids | 20 |
| Distinguishing Tests and Identification | 20 |
| Reaction Mechanism and Reactivity | 20 |
| PYQ Final | 20 |
| Revision Master | 20 |
| Acidity of Carboxylic Acids | 19 |
| Acidity and Comparative Reactivity | 19 |
Questions students ask
Is Aldehydes, Ketones and Carboxylic Acids important for NEET?
Very important — it is one of the highest-weightage Organic Chemistry chapters. Name reactions, distinguishing tests and acidity comparisons are tested every year.
Which topics should I revise first?
Focus on aldol condensation and Cannizzaro reaction conditions, Tollens' vs Fehling's test, Clemmensen vs Wolff-Kishner reduction, and the effect of substituents on carboxylic acid acidity.
How many questions from this chapter are on RankUp?
The RankUp app has 665 questions on Aldehydes, Ketones and Carboxylic Acids, including 300 ELITE questions. Every question has a detailed explanation.
