Important Chemical Reactions for Class 12 Chemistry

Here are some important chemical reactions which every student of Class 12 must have a thorough understanding of.

Most Important Chemical Reactions Class 12th Chemistry

Sandmeyer Reaction:

The Sandmeyer reaction is a chemical reaction which is used to synthesize aryl halides from aryl diazonium salts. This reaction is a method for substitution of an aromatic amino group by preparing diazonium salt, that is followed by its displacement and copper salts often catalyze it.

Sandmeyer Reaction

The Br, Cl and Cn nucleophiles can be easily present in the benzene ring of benzene diazonium salt in the presence of Copper ion.

Gattermann Reaction:

Bromine and Chlorine can be present in the benzene ring by preparing the benzene diazonium salt solution with similar halogen acid present with copper powder. This is the Gattermann Reaction.

Gattermann Reaction

Balz-Schiemann Reaction:

When arene-diazonium chloride is prepared with fluoroboric acid, arene diazonium fluoroborate is precipitated and decomposes to yield aryl fluoride which on heating.

Balz-Schiemann Reaction

Finkelstein Reaction:

In the Finkelstein Reaction Alkyl iodides are prepared easily by the reaction of alkyl chlorides with Nal in dry acetone.

Finkelstein Reaction

Swarts Reaction:

When alkyl chloride is heated in the presence of a metallic fluoride like AgF, Hg2F2, SbF3 or CoF2, we get alkyl fluorides.

Swarts Reaction

Wurtz Reaction:

When Alkyl halides react with sodium with dry ether, we get hydrocarbons that include the double number of carbon atoms present in the halide. This is known as the Wurtz Reaction

Wurtz Reaction

Wurtz-Fittig Reaction:

When a mixture of alkyl halide and aryl halide gets treated with sodium in dry ether, we get an alkyl arene.Wurtz-Fittig Reaction

Fittig Reaction:

Aryl halides prepared with sodium in dry ether to give analogous compounds where two aryl groups joined.

Fittig Reaction

Friedel-Crafts alkylation Reaction:

Benzene is prepared with an alkyl halide in the presence of anhydrous aluminum chloride to give Alkylbenzene.

Friedel-Crafts alkylation ReactionFriedel-Crafts alkylation ReactionFriedel-Crafts alkylation Reaction

This is the Friedel-Crafts alkylation Reaction

Friedel-Crafts acylation reaction:

We get acyl benzene when an acyl halide is reacted with benzene in the presence of Lewis acids.

Friedel-Crafts acylation reactionFriedel-Crafts acylation reactionFriedel-Crafts acylation reaction. 

Reimer-Tiemann Reaction:

When preparing phenol with chloroform in the presence of sodium hydroxide, -CHO group is present at the ortho position of the benzene ring, which results into salicylaldehyde.

Reimer-Tiemann Reaction

Kolbe’s Reaction:

Phenol reacts with sodium hydroxide to give sodium phenoxide which then reacts with carbon dioxide in acidic medium to give hydroxybenzoic acid.

Kolbe’s Reaction

Rosenmund Reduction:

When Acyl chloride is hydrogenated to an aldehyde over a catalyst, known as Rosenmund catalyst which is either palladium or barium sulfate.

Rosenmund Reduction

Stephen reaction:

Nitriles with stannous chloride in the presence of hydrochloric acid reduced to the corresponding imine and give the corresponding aldehyde after hydrolysis.

Stephen reaction

Etard reaction:

Chromyl chloride oxidizes methyl group to get chromium complex which on hydrolysis provides corresponding benzaldehyde.

Etard reaction

Gatterman – Koch reaction:

Benzene is prepared with carbon monoxide and hydrogen chloride in the presence of anhydrous aluminum chloride to give benzaldehyde.

Gatterman – Koch reaction

Clemmensen Reduction:

In Clemmensen reduction, Carbonyl group of aldehydes and ketones on treatment with zinc-amalgam and concentrated hydrochloric acid reduced to CH2 group.

Clemmensen Reduction

Wolff Kishner Reduction:

Carbonyl group of aldehydes and ketones on treatment with hydrazine which on heating with sodium hydroxide in a high boiling solvent (ethylene glycol) reduced to CH2 group.

Wolff Kishner Reduction

Tollens’ test:

Heating an aldehyde with fresh prepared ammoniacal silver nitrate solution produces a bright silver mirror due to the formation of silver metal.

Tollens’ test

Fehling’s test:

Fehling’s solution A (aqueous copper sulfate) and Fehling solution B (alkaline sodium potassium tartrate) are mixed in equal amounts before the test. A reddish brown precipitate is obtained when an aldehyde is heated with Fehling’s reagent.

Fehling’s test

Aldol reaction:

Aldehydes and ketones having one α-hydrogen undergo a reaction in the presence of dilute alkali as the catalyst to produce β-hydroxy aldehydes or β-hydroxy ketones.

Aldol condensation:

Aldol and Ketol lose water to provide α,β-unsaturated carbonyl compounds which are aldol condensation products.

Aldol condensation

Cross aldol condensation:

Aldol condensation is carried out between two different aldehydes and ketones. It gives a mixture of four products if both of them include α-hydrogen atoms.

Cross aldol condensation

Cannizzaro reaction:

Aldehydes without α-hydrogen atom undergo self-oxidation and reduction reaction when prepared with concentrated alkali.

Cannizzaro reaction

Kolbe electrolysis:

in Kolbe electrolysis, An aqueous solution of sodium or potassium salt of a carboxylic acid gives alkane containing an even number of carbon atoms on electrolysis.

Kolbe electrolysis

Hell-Volhard-Zelinsky (HVZ )reaction:

Carboxylic acids having a α-hydrogen are halogenated at the α-position give α-halo carboxylic acids on treatment with chlorine or bromine in the presence of small amount of red phosphorus.

Hell-Volhard-Zelinsky (HVZ )reaction

Gabriel phthalimide synthesis:

Phthalimide prepared with ethanolic potassium hydroxide produces potassium salt of phthalimide when heated with alkyl halide followed by alkaline hydrolysis forms the corresponding primary amine.

Gabriel phthalimide synthesis

Hoffmann bromamide degradation reaction:

An amide with bromine in an aqueous solution of sodium hydroxide produces primary amines. Migration of an alkyl or aryl group takes place from carbonyl carbon of the amide to the nitrogen atom. The amine so produced include one carbon less than that present in the amide.

Hoffmann bromamide degradation reaction

Carbylamine reaction:

Aliphatic and aromatic primary amines when heated with chloroform and ethanolic potassium hydroxide produces isocyanides or carbyl amines which are foul smelling substances.

Carbylamine reaction

Hinsberg’s Test:

Benzenesulfonyl chloride (C6H5SO2Cl) reacts with primary and secondary amines to produce sulphonamides.

The reaction of benzene-sulfonyl chloride with primary amine yields N-ethyl benzene-sulfonyl amide. The hydrogen attached to the nitrogen in sulphonamide is strongly acidic due to the presence of strong electron withdrawing sulfonyl group. Hence, it is soluble in alkali. Hinsberg’s Test

In the reaction with a secondary amine, N, N-diethyl- benzenesulfonamide is formed. Since N, N- diethyl benzene sulphonamide does not contain any hydrogen atom attached to a nitrogen atom, it is not acidic and hence insoluble in alkali.

Hinsberg’s Test

Tertiary amines do not react with benzene-sulfonyl chloride.

Coupling Reactions:

Benzene diazonium chloride gets reacted with phenol in which the phenol molecule at its para position is mixed with the diazonium salt to give p-hydroxyazobenzene.

Coupling Reactions

To know more about Chemical Reactions in detail, register with ExamHub’s.

Test your Knowledge on Important Chemical Reactions!!