Reactions in Organic Chemistry Class 12

Dhristi JEE 2022-24

An introduction to Class 12 Organic Chemistry

Organic chemistry is a branch of chemistry that deals with different types of reactions. Some of the reactions are known by the names reactions because these reactions are named after their researcher or developer. In this article, all the important name reactions of organic chemistry are provided. The class 12 chemistry important name reactions are essential to know for the exams and given below are all naming reactions of class 12 chemistry that you can refer to for learning.


Name Reactions of Organic Chemistry for Class 12

Some of the important name reactions are explained below with their equation.


  1.  Sandmeyer Reaction:

The Sandmeyer reaction is a chemical reaction that is used in the synthesis of the aryl halides from the aryl diazonium salts. This reaction is a method for the substitution of the aromatic amino group by the preparation of the diazonium salt, which is then followed by its displacement and here, the copper salts often catalyzes the reaction.


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The Cl, Br and Cn nucleophiles are easily present in the benzene ring of the benzene diazonium salt when the copper ion is present.


  1. Gattermann Reaction:

In the Gattermann reaction, aromatic compounds are produced by a mixture of hydrogen cyanide and hydrogen chloride in the presence of a Lewis acid catalyst for example AlCl3. This is known as the Gattermann Reaction.


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  1.  Balz-Schiemann Reaction:

When the arene-diazonium chloride is prepared with the fluoroboric acid, the arene diazonium fluoroborate gets precipitated and decomposes for yielding aryl fluoride.


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  1.  Finkelstein Reaction:

In the Finkelstein Reaction, the alkyl iodides are prepared by the reaction of the alkyl chlorides or alkyl bromide with Nal in the presence of dry acetone.


R-X+NaI→R-I+NaX  where X= Cl, Br


  1. Swarts Reaction:

When an alkyl chloride is heated in the presence of metallic fluorides such as  AgF, Hg2F2, CoF2 or SbF, alkyl fluorides are formed.


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  1.  Wurtz Reaction:

When the alkyl halides tend to react with the sodium with dry ether, hydrocarbons are formed which include double the number of carbon atoms that are present in the halide. This is called the Wurtz Reaction.


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  1. Wurtz-Fittig Reaction:

When the mixture of an alkyl halide and aryl halide gets treated with the sodium in dry ether, an alkyl arene is formed.


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  1.  Fittig Reaction:

Aryl halides are prepared with sodium in the dry ether that gives analogous compounds wherein two aryl groups are joined.


Ar-X  +  2Na  +  X-Ar →Ar-Ar + 2NaX  


  1.  Friedel-Crafts alkylation Reaction:

Benzene is prepared with the alkyl halide in the presence of anhydrous aluminium chloride to yield an alkylbenzene.


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  1.  Friedel-Crafts Acylation Reaction:

We can get acyl benzene when the acyl halide gets reacted with the benzene in the presence of Lewis acids.


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  1.  Reimer-Tiemann Reaction:

When we prepare phenol with chloroform in the presence of sodium hydroxide, the -CHO group is present in the ortho position of the benzene ring gives us salicylaldehyde.


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  1.  Kolbe’s Reaction:

Phenol tends to react with the sodium hydroxide to yield sodium phenoxide which then tends to react with the carbon dioxide in an acidic medium to give us hydroxybenzoic acid.


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  1.  Rosenmund Reduction:

When an acyl chloride is hydrogenated to an aldehyde over the presence of a catalyst, it is known as Rosenmund catalyst and it is either a palladium or barium sulfate.


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  1.  Stephen Reaction:

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


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  1.  Etard Reaction:

The chromyl chloride oxidizes the methyl group to yield a chromium complex which on hydrolysis provides us with the corresponding benzaldehyde.


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  1.  Gattermann – Koch Reaction:

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


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  1.  Clemmensen Reduction:

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


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  1.  Wolff Kishner Reduction:

The carbonyl group of the aldehydes and ketones on treatment with the hydrazine, which again on heating with the sodium or potassium hydroxide in a high boiling solvent like ethylene glycol gets reduced to the CH2 group.


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  1.  Tollens’ Test:

On heating an aldehyde with the freshly prepared ammoniacal silver nitrate solution it produces a bright silver mirror because of the formation of the silver medal. A few drops of sodium hydroxide is added so that silver nitrate can be converted into silver hydroxide.


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  1.  Fehling’s Test:

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


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  1.  Aldol Reaction:

Both aldehydes and ketones having one α-hydrogen tend to undergo a reaction in the presence of a dilute alkali as the catalyst for yielding either β-hydroxy aldehydes or β-hydroxy ketones.


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  1. Aldol Condensation:

Aldol and ketol tend to lose water to yield α,β-unsaturated carbonyl compounds that are known as the aldol condensation products.


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  1.  Cross Aldol Condensation:

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


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  1.  Cannizzaro Reaction:

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


2 C6H5CHO + KOH → C6H5CH2OH + C6H5COOK


  1.  Kolbe Electrolysis:

In the Kolbe electrolysis, an aqueous solution of either sodium or potassium salt of the carboxylic acid provides an alkane that contains an even number of carbon atoms on electrolysis.


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  1.  Hell-Volhard-Zelinsky (HVZ )Reaction:

Carboxylic acids that have an α-hydrogen are halogenated at the α-position to give α-halo carboxylic acids when they are treated with either chlorine or bromine in the presence of a small amount of the red phosphorus.


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  1.  Gabriel Phthalimide Synthesis:

The phthalimide prepared with the ethanolic potassium hydroxide tends to produce a  potassium salt of the phthalimide when it is heated with an alkyl halide followed by alkaline hydrolysis to form the corresponding primary amine.


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  1.  Hoffmann Bromamide Degradation Reaction:

An amide with the bromine in an aqueous solution of sodium hydroxide gives us primary amines. Migration of either an alkyl or aryl group takes place from the carbonyl carbon of the amide to the nitrogen atom. The amine which is produced includes one carbon less than what is present in the amide.


R-CO-NH2 + Br2 + 4NaOH → R-NH₂ + Na2CO3 + 2NaBr + 2H₂O 


  1.  Carbylamine Reaction:

The aliphatic and the aromatic primary amines, when heated with the chloroform and ethanolic potassium hydroxide, yields isocyanides or carbonyl amines which are foul-smelling substances.


Me3CNH2 + CHCl3 + 3 NaOH →Me3CNC + 3 NaCl + 3 H2O


  1.   Hinsberg’s Test:

Benzenesulfonyl chloride C6H5SO2Cl tends to react with the primary and secondary amines to give sulphonamides.

  1. The reaction of benzene-sulfonyl chloride with the primary amine produces N-ethyl benzene-sulfonyl amide. The hydrogen which is attached to the nitrogen in sulphonamide is strongly acidic because of the presence of the strong electron-withdrawing sulfonyl group. Therefore, it is soluble in alkali. 

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

  3. Tertiary amines do not tend to react with benzene-sulfonyl chloride.


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  1.   Coupling Reactions:

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


An example of a coupling reaction (homo-coupling reaction) is the Ullmann reaction which is given below.


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Conclusion

Named chemical reactions are now an important part of organic chemistry, which is improving its ability to create increasingly complex and diversified chemical compounds. Many new chemical reactions are reported nowadays and named after their discoverers in honor of their significant contribution to synthetic organic chemistry. This article covered all the important name reactions with their chemical equations.

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