12th Chemistry Named Reactions List with Products (Samacheer Kalvi)
Named reactions are where a lot of Class 12 Chemistry marks are won and lost. Students usually try to memorise them as an alphabetical list, which is the hardest possible way to learn them, because the exam never asks for a name in isolation. It asks what a given starting material becomes with a given reagent.
So group them by what they do.
Reactions that add a carbon or build a chain
- Kolbe reaction. Phenol with carbon dioxide under pressure in alkaline conditions gives salicylic acid.
- Reimer-Tiemann reaction. Phenol with chloroform and alkali gives salicylaldehyde.
- Friedel-Crafts alkylation and acylation. Aromatic ring plus alkyl or acyl halide with anhydrous aluminium chloride.
- Wurtz reaction. Alkyl halide with sodium in dry ether gives a longer alkane.
- Aldol condensation. Two aldehyde or ketone molecules with alpha hydrogens, under dilute alkali, give a beta hydroxy carbonyl compound.
- Perkin reaction. Aromatic aldehyde with acid anhydride and its sodium salt gives an unsaturated aromatic acid.
Reactions that reduce
- Clemmensen reduction. Carbonyl to methylene using zinc amalgam and hydrochloric acid. Use in acidic conditions.
- Wolff-Kishner reduction. Same conversion, but with hydrazine and a base. Use in basic conditions.
- Rosenmund reduction. Acid chloride to aldehyde over palladium poisoned with barium sulphate.
- Stephen reaction. Nitrile to aldehyde using stannous chloride and hydrochloric acid.
- Gattermann-Koch reaction. Benzene with carbon monoxide and hydrochloric acid gives benzaldehyde.
Clemmensen and Wolff-Kishner do the same job. The only reason both exist is that one works when the molecule cannot survive acid and the other when it cannot survive base. Questions test exactly that.
Reactions that oxidise or cleave
- Cannizzaro reaction. An aldehyde with no alpha hydrogen, with concentrated alkali, disproportionates into an alcohol and a carboxylate.
- Etard reaction. Toluene with chromyl chloride gives benzaldehyde.
- Haloform or iodoform reaction. Methyl ketones and ethanol give a yellow iodoform precipitate. Also a distinguishing test.
- Hunsdiecker reaction. Silver salt of a carboxylic acid with bromine gives an alkyl halide with one fewer carbon.
The absence of an alpha hydrogen is the whole trigger for Cannizzaro. If a question gives you formaldehyde or benzaldehyde with concentrated alkali, that is what it wants.
Reactions involving nitrogen
- Hofmann bromamide degradation. Amide with bromine and alkali gives a primary amine with one fewer carbon.
- Gabriel phthalimide synthesis. Gives pure primary amines only.
- Carbylamine reaction. Primary amine with chloroform and alcoholic potassium hydroxide gives a foul smelling isocyanide. A test for primary amines.
- Hinsberg test. Distinguishes primary, secondary and tertiary amines.
- Sandmeyer and Gattermann reactions. Diazonium salt to aryl halide, differing in the catalyst used.
- Balz-Schiemann reaction. Diazonium salt to aryl fluoride.
- Coupling reaction. Diazonium salt with phenol or aniline gives a coloured azo dye.
Gabriel synthesis fails for aromatic primary amines, and that limitation is itself a frequently asked question.
Rearrangements and miscellaneous
- Williamson ether synthesis. Alkoxide with alkyl halide. Works poorly with tertiary halides because elimination competes.
- Kolbe electrolysis. Electrolysis of a carboxylate salt gives an alkane.
- Schotten-Baumann reaction. Benzoylation of alcohols and amines.
- Fittig and Wurtz-Fittig reactions. Aryl halide couplings.
The reagent-first method
Rather than memorising reactions, memorise what each reagent does. Then most conversion questions become one step.
| Reagent | What it does |
|---|---|
| LiAlH4 | Strong reducing agent, reduces acids, esters, amides and nitriles |
| NaBH4 | Milder, reduces aldehydes and ketones but not acids or esters |
| PCC | Oxidises primary alcohol to aldehyde and stops there |
| Hot alkaline KMnO4 | Strong oxidation, side chain to carboxylic acid |
| Tollens reagent | Silver mirror with aldehydes, not ketones |
| Fehling solution | Red precipitate with aliphatic aldehydes |
| Zn-Hg with HCl | Carbonyl to methylene in acid |
| Hydrazine with base | Carbonyl to methylene in base |
Once this table is fluent, a question like "convert acetophenone to ethylbenzene" needs no reaction name at all. You need a carbonyl-to-methylene reduction, you check whether the conditions can be acidic, and you choose accordingly.
How to revise these
Write each reaction as a conversion arrow with the reagent above it, not as a paragraph. Then cover the product and reproduce it. Twenty conversions a day for a week will cover the whole organic block, and it is far more effective than reading the chapter again.
More Class 12 practice material is available on the Class 12 section.