Aldehydes, Ketones and Carboxylic Acids

NCERT Class 12 Chemistry Chapter 8

Aldehydes, Ketones and Carboxylic Acids for Class 12 Chemistry, JEE and NEET: nucleophilic addition, named reactions, tests for aldehydes, acid strength.

13 topics Updated 8 Nov 2026

For: Class 12, JEE and NEET, unless a topic says otherwise

In the syllabus: JEE Class 12 syllabus, NEET Class 12 syllabus

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NCERT Chemistry Part II (Class 12), Chapter 8 “Aldehydes, Ketones and Carboxylic Acids”, reprint 2026-27.

Open the official NCERT chapter (PDF, 4.4 MB, ncert.nic.in) (opens in a new tab)

Checked on 19 Oct 2026.

Learn in this order

Carbonyl group: nomenclature and structure
Common and IUPAC names (NCERT Table 8.1), how the two differ, and why the C=O group is planar and polar.

NCERT Section 8.1 11 min read 2 solved examples 7 practice questions
Preparation of aldehydes and ketones
Rosenmund, Stephen, Etard and Gattermann–Koch reactions, DIBAL-H, R_₂Cd and Friedel–Crafts.

NCERT Section 8.2 12 min read 3 solved examples 7 practice questions
Physical properties of aldehydes and ketones
Boiling points against alkanes, ethers and alcohols, and solubility in water.

NCERT Section 8.3 8 min read 2 solved examples 6 practice questions
Reactions of aldehydes and ketones
Nucleophilic addition, reductions, Tollens’ test, aldol, Cannizzaro and haloform.

NCERT Section 8.4 16 min read 3 solved examples 7 practice questions
Experiment: tests for aldehydes and ketones
2,4-DNP for the carbonyl group, then Schiff’s, Fehling’s, Benedict’s and Tollens’ for aldehydes.

JEE and NEET only 12 min read 2 solved examples 6 practice questions
Experiment: preparation of iodoform
The haloform reaction of acetone or ethanol with iodine and alkali, Remsen’s 1903 method and the yellow crystals.

JEE and NEET only 9 min read 2 solved examples 6 practice questions
Uses of aldehydes and ketones
Formalin and bakelite, acetaldehyde as a starting material, solvents, perfumes and flavours.

NCERT Section 8.5 6 min read 2 solved examples 6 practice questions
Carboxyl group: nomenclature and structure
Common and IUPAC names (NCERT Table 8.3), dioic acids, and how –COOH differs from a carbonyl group.

NCERT Section 8.6 10 min read 2 solved examples 6 practice questions
Preparation of carboxylic acids
Oxidising alcohols and alkylbenzenes, nitriles, Grignard reagents with CO_₂, and hydrolysis.

NCERT Section 8.7 10 min read 3 solved examples 6 practice questions
Physical properties of carboxylic acids
Hydrogen-bonded dimers, high boiling points, and solubility in water.

NCERT Section 8.8 9 min read 2 solved examples 6 practice questions
Chemical reactions of carboxylic acids
Acidity and substituents, esterification, acyl chlorides, reduction, decarboxylation and HVZ.

NCERT Section 8.9 18 min read 4 solved examples 8 practice questions
Experiment: tests for the carboxyl group
Blue litmus, effervescence with sodium hydrogencarbonate, and the sweet-smelling ester test.

JEE and NEET only 9 min read 2 solved examples 6 practice questions
Uses of carboxylic acids
Formic and acetic acid, vinegar, nylon-6,6, sodium benzoate, and soaps from fatty acids.

NCERT Section 8.10 9 min read 3 solved examples 6 practice questions

Key formulas in this chapter

Carbonyl group: names and structure

Aldehyde: R–CHO
Ketone: R–CO–R′
Open-chain aldehydes: α-carbon = IUPAC C2, β = C3, γ = C4; ring carbaldehydes: α = ring C1
Carbonyl carbon: sp^², trigonal planar, bond angles about 120°
Resonance: >C=O ↔ >C^⁺–O^⁻

Preparation of aldehydes and ketones

RCOCl + H_₂ → RCHO + HCl (Pd–BaSO_₄, Rosenmund)
RCN → RCH=NH → RCHO (SnCl_₂ and HCl, then H_₃O^⁺; Stephen)
C_₆H_₅CH_₃ → C_₆H_₅CHO (CrO_₂Cl_₂ in CS_₂, then H_₃O^⁺; Etard)
C_₆H_₆ + CO → C_₆H_₅CHO (HCl, anhydrous AlCl_₃ with CuCl; Gattermann–Koch)
2R′COCl + R_₂Cd → 2R′COR + CdCl_₂

Physical properties of aldehydes and ketones

General b.p. trend at similar mass: alkanes and ethers < aldehydes and ketones < alcohols
n-butane 273 K, methoxyethane 281 K, propanal 322 K, acetone 329 K, propan-1-ol 370 K

Reactions of aldehydes and ketones

RCHO + 2[Ag(NH_₃)_₂]^⁺ + 3OH^⁻ → RCOO^⁻ + 2Ag + 2H_₂O + 4NH_₃
RCHO + 2Cu^²⁺ + 5OH^⁻ → RCOO^⁻ + Cu_₂O + 3H_₂O
C=O + H_₂N–Z → >C=N–Z + H_₂O
2CH_₃CHO (dil. NaOH) → CH_₃CH(OH)CH_₂CHO (heat) → CH_₃CH=CHCHO + H_₂O
2HCHO + KOH → CH_₃OH + HCOOK (Cannizzaro)

Experiment: tests for aldehydes and ketones

R_₂C=O + H_₂N–NH–C_₆H_₃(NO_₂)_₂ → R_₂C=N–NH–C_₆H_₃(NO_₂)_₂ + H_₂O
RCHO + 2[Ag(NH_₃)_₂]^⁺ + 3OH^⁻ → RCOO^⁻ + 2Ag + 2H_₂O + 4NH_₃
RCHO + 2Cu^²⁺ + 5OH^⁻ → RCOO^⁻ + Cu_₂O + 3H_₂O

Experiment: preparation of iodoform

CH_₃COCH_₃ + 3I_₂ + 4NaOH → CHI_₃ + CH_₃COONa + 3NaI + 3H_₂O
RCOCH_₃ + 3NaOI → RCOONa + CHI_₃ + 2NaOH
Iodoform, CHI_₃: yellow crystals, m.p. 119 °C

Uses of aldehydes and ketones

Formalin: NCERT 40% solution (commercially about 37% HCHO by mass)
Bakelite: a phenol-formaldehyde resin
Industrial solvents: acetone, ethyl methyl ketone

Carboxyl group: names and structure

R–COOH: alkane − e + oic acid; COOH carbon = C1
HOOC–COOH: ethanedioic acid; HOOC–(CH_₂)_₄–COOH: hexanedioic acid
Carboxyl carbon: planar, about 120°

Preparation of carboxylic acids

RCH_₂OH → RCOOH (KMnO_₄, or CrO_₃–H_₂SO_₄)
C_₆H_₅R → C_₆H_₅COOH (KMnO_₄–KOH, heat; then H_₃O^⁺)
R–CN → R–CONH_₂ → RCOOH (acidic hydrolysis, or alkali followed by acidification)
RMgX + CO_₂ → RCOOMgX → RCOOH (H_₃O^⁺)
RCOCl + H_₂O → RCOOH + HCl

Physical properties of carboxylic acids

General b.p. trend at similar mass: ether < aldehyde < alcohol < carboxylic acid
methoxyethane 281 K, propanal 322 K, propan-1-ol 370 K, ethanoic acid 391.1 K
2RCOOH ⇌ (RCOOH)_₂, in the vapour and in nonpolar solvents

Chemical reactions of carboxylic acids

pK_a = −log K_a
RCOOH + NaHCO_₃ → RCOONa + H_₂O + CO_₂
RCOOH + R′OH ⇌ RCOOR′ + H_₂O (H^⁺)
RCOOH + SOCl_₂ → RCOCl + SO_₂ + HCl
RCOOH → RCH_₂OH (LiAlH_₄ or B_₂H_₆, then H_₃O^⁺)
RCOONa + NaOH → RH + Na_₂CO_₃ (CaO, heat)
RCH_₂COOH → RCH(X)COOH (X_₂/red P, then H_₂O)

Experiment: tests for the carboxyl group

RCOOH + NaHCO_₃ → RCOONa + H_₂O + CO_₂
RCOOH + R′OH ⇌ RCOOR′ + H_₂O (conc. H_₂SO_₄, heat)

Uses of carboxylic acids

Vinegar: 5–8% acetic acid in water
Hexanedioic acid: HOOC(CH_₂)_₄COOH, for nylon-6,6
RCOOH + NaHCO_₃ → RCOONa + H_₂O + CO_₂
Soap: RCOO^⁻Na^⁺ or RCOO^⁻K^⁺, R a long carbon chain

Learn in this order

Key formulas in this chapter

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