On this page
Most students meet named reactions as a list at the end of each NCERT chapter, and by exam week Rosenmund, Stephen, Etard and Cannizzaro blur together. This post sorts them by what they do to a molecule, picks out the pairs that are easy to confuse, and ends with a board question.
Why do named reactions blur together?
A name tells you nothing about the chemistry, so a memorised list leaves each fact on its own with nothing to hold it.
In a study of students in an organic chemistry course, Grove and Bretz (2012) described rote memorisation and meaningful learning not as two boxes but as ends of a continuum. Moving towards the meaningful end means linking each fact to what you know: which bond changes, and why that reagent does it.
A map builds those links. A meta-analysis by Nesbit and Adesope (2006) pooled 55 studies with 5,818 participants and found that constructing, modifying or viewing concept maps was associated with better knowledge retention, with effect sizes that varied from small to large depending on how the maps were used.
How should you sort the named reactions?
Group them by what happens to the carbon skeleton. Every reaction below appears in the NCERT Class 11 and 12 chemistry units on hydrocarbons, haloalkanes, alcohols and phenols, aldehydes, ketones and acids and amines.
1. Same carbon count, new functional group
Finkelstein: alkyl chloride or bromide to alkyl iodide with NaI in dry acetone.
Swarts: alkyl halide to alkyl fluoride with AgF, Hg₂F₂, CoF₂ or SbF₃.
Rosenmund reduction: acyl chloride to aldehyde with H₂ over Pd on BaSO₄.
Stephen reaction: nitrile to aldehyde with SnCl₂ and HCl, then hydrolysis.
Etard reaction: methyl group on a benzene ring to –CHO with chromyl chloride.
Clemmensen and Wolff–Kishner reductions: C=O to CH₂.
Sandmeyer: diazonium group to –Cl or –Br with Cu₂Cl₂ or Cu₂Br₂.
2. Carbon added
Wurtz: two alkyl halides joined with sodium in dry ether. Wurtz–Fittig joins an alkyl and an aryl halide; Fittig joins two aryl halides.
Friedel–Crafts alkylation and acylation: an alkyl or acyl group added to a ring.
Gattermann–Koch: –CHO added to benzene with CO and HCl.
Kolbe's reaction: phenoxide plus CO₂ gives ortho-hydroxybenzoic acid.
Reimer–Tiemann: phenol plus chloroform and NaOH puts –CHO at the ortho position.
Aldol: two carbonyl molecules joined to give a β-hydroxy aldehyde or ketone.
3. Carbon removed
Hoffmann bromamide degradation: amide to primary amine with one carbon fewer.
Decarboxylation: sodium salt of an acid heated with soda lime gives an alkane with one carbon fewer.
Haloform reaction: a methyl ketone gives a carboxylate with one carbon fewer.
4. Needs a special condition
Aldol needs at least one α-hydrogen. Cannizzaro works only on aldehydes with no α-hydrogen, which disproportionate in concentrated alkali into an alcohol and a carboxylate.
Hell–Volhard–Zelinsky halogenates a carboxylic acid at the α-position, so it also needs an α-hydrogen.
Which pairs do students mix up?
Gattermann vs Gattermann–Koch. Gattermann replaces a diazonium group with a halogen using copper and HX. Gattermann–Koch adds –CHO to benzene with CO and HCl.
Kolbe's reaction vs Kolbe's electrolysis. The first puts –COOH on phenol. The second electrolyses a carboxylate salt to join two alkyl groups into an alkane.
Clemmensen vs Wolff–Kishner. Both turn C=O into CH₂. Clemmensen uses zinc amalgam and concentrated HCl (acidic). Wolff–Kishner uses hydrazine, then KOH in ethylene glycol with heat (basic). Pick the one the rest of the molecule can survive.
Aldol vs Cannizzaro. Look for an α-hydrogen first. It decides which one can happen.
Worked example: a board question
The CBSE Class XII Chemistry sample paper for 2026–27, Question 24, asks you to name each reaction and fill the gap:
2CH₃CHO → CH₃CH(OH)CH₂CHO. Two aldehydes joined, a β-hydroxy aldehyde formed: aldol condensation, reagent dilute NaOH. Ethanal has α-hydrogens, so this is allowed.
Toluene with a reagent in CS₂ gives a chromium complex, which on hydrolysis gives benzaldehyde. A ring methyl becomes –CHO: Etard reaction, reagent CrO₂Cl₂.
A ketone with NH₂NH₂ loses water to give an intermediate, which with KOH and ethylene glycol on heating gives >CH₂ and N₂: Wolff–Kishner reduction, intermediate the hydrazone >C=N–NH₂.
The marking scheme gives half a mark for each name and half for each missing reagent or product, so a name without the reagent loses half the marks.
What do the entrance exam syllabi name?
The JEE (Main) 2026 syllabus and the NEET (UG) 2026 syllabus name only a few directly, such as Reimer–Tiemann, Wolff–Kishner, Clemmensen, aldol, Cannizzaro and haloform, with Friedel–Crafts also in the JEE list. The rest sit inside phrases like "general methods of preparation", so learn the full NCERT set. Check the syllabus for your exam year.
Mechanisms make the map stick. Our post on learning mechanisms rather than lists explains how, and the next step after the map is planning conversions from one compound to another. If a single reaction still makes no sense, the Fermi Concept Library covers every concept in chemistry, each with its own lesson, so you can fix that one gap.
A practice routine for two weeks
Days 1 to 3: Build the four-heading map from memory, one chapter at a time, then correct it.
Days 4 to 7: Write ten reactions a day as "start, reagent, product" with one item hidden, and fill it in.
Days 8 to 10: Do the confusing pairs as two-column comparisons.
Days 11 to 14: Solve one board paper's named reaction questions and add anything you missed to the map.
Tonight, draw the four headings on a blank page and fill in as many reactions as you can in ten minutes without your book.
