CBSE Chemistry Class 12: All 15 Name Reactions You Must Know

CBSE boards ask name reactions in Organic Chemistry almost every year. Here are all 15 you must know — reagents, conditions, what the reaction does, and how boards frame the question.

Name reactions in Organic Chemistry are high-yield, high-repeatability questions in CBSE boards. They're asked as 'give the reaction', 'identify the reagents', 'what is the product', or 'name the reaction for this transformation'. The good news: there are only about 15 that boards consistently test. Knowing all 15 cold is achievable in a single revision session.

Carbonyl Chemistry Reactions

• Aldol condensation: An aldehyde or ketone with an α-hydrogen undergoes base-catalysed self-condensation to form a β-hydroxy carbonyl compound, which can then dehydrate to give an α,β-unsaturated carbonyl. Reagent: NaOH (dilute).
• Cannizzaro reaction: A non-enolisable aldehyde (no α-H, e.g. HCHO or PhCHO) undergoes disproportionation in concentrated NaOH — one molecule is oxidised to carboxylate, another is reduced to alcohol. Reagent: Conc. NaOH.
• Clemmensen reduction: Converts a carbonyl group (C=O) to a methylene group (CH₂) under acidic conditions. Used when the molecule is acid-stable. Reagent: Zn/Hg amalgam + conc. HCl.
• Wolff–Kishner reduction: Same conversion as Clemmensen (C=O → CH₂) but under basic conditions. Used when the molecule is base-stable. Reagent: Hydrazine (N₂H₄) + KOH in ethylene glycol, heat.

Phenol and Arene Reactions

• Reimer–Tiemann reaction: Phenol reacts with chloroform in the presence of NaOH to give ortho-hydroxybenzaldehyde (salicylaldehyde) as the major product. Boards ask: 'What is the product when phenol reacts with CHCl₃/NaOH?'
• Kolbe's reaction: Sodium phenoxide reacts with CO₂ under high pressure and temperature to give sodium salicylate (which on acidification gives salicylic acid). Memorise: phenol → sodium phenoxide + CO₂ (ΔP, ΔT) → salicylic acid.
• Williamson's ether synthesis: An alkoxide ion (RO⁻) reacts with a primary alkyl halide via SN2 to form an ether. Limited to primary halides — secondary and tertiary give elimination products with strong bases.

Amine and Nitrogen Reactions

• Hofmann bromamide degradation: A primary amide (RCONH₂) treated with Br₂ and NaOH gives a primary amine (RNH₂) with one fewer carbon. Used to convert amides to amines. Note: the product has one fewer carbon than the starting material.
• Gabriel phthalimide synthesis: The potassium salt of phthalimide reacts with an alkyl halide (SN2), then undergoes hydrolysis to give a primary amine. Limitation: only gives primary amines.
• Hinsberg test: Used to distinguish primary, secondary, and tertiary amines. Reagent: benzenesulphonyl chloride (C₆H₅SO₂Cl). Result: 1° amines → soluble product in NaOH; 2° amines → insoluble product; 3° amines → no reaction.
• Diazotisation: A primary aromatic amine reacts with NaNO₂ + HCl at 0–5°C to form a diazonium salt (ArN₂⁺Cl⁻). Temperature is critical — above 5°C, the diazonium salt decomposes. Used for coupling reactions.
• Sandmeyer reaction: Diazonium salt reacts with CuCl, CuBr, or CuCN to replace the −N₂⁺ group with −Cl, −Br, or −CN respectively. Named for Traugott Sandmeyer.

Identification Reactions (Distinguishing Tests)

• Lucas test: Distinguishes primary, secondary, and tertiary alcohols. Reagent: ZnCl₂ + conc. HCl. Result: 3° → immediate turbidity; 2° → turbidity within 5 minutes; 1° → no reaction at room temperature.
• Iodoform test: Detects the CH₃CO− group (methyl ketones and ethanol). Reagent: I₂ + NaOH. Result: yellow precipitate of CHI₃ (iodoform) with characteristic smell. Acetaldehyde gives a positive test; other aldehydes do not.
• Fehling's test / Tollens' test: Both distinguish aldehydes from ketones. Aldehydes are oxidised (positive result); ketones are not. Tollens' gives a silver mirror; Fehling's gives a brick-red precipitate of Cu₂O.

How Boards Frame These Questions

CBSE board questions on name reactions typically take four forms: (1) 'Give the reaction for...' — you write the equation and conditions; (2) 'What is the product when X reacts with Y?' — you identify the reaction type and write the product; (3) 'Name the reaction' — given an equation, you name it; (4) 'How will you distinguish between A and B?' — a test question combining two reactions.