chemical reactions for cbse class 12 - Overview, Structure, Properties & Uses

Important Chemical Reactions For cbse Class 12 - Reaction and FAQs

Edited By Team Careers360 | Updated on Jul 21, 2022 03:39 PM IST

Chemical Reaction

The reactions in which some bonds get broken towards reactant molecule and forms new bonds toward product molecules which further form new substances. Reactant are those substances which are generally present at left side and products are present on right hand side. There are many types of chemical reaction out of which some important chemical reaction/important reactions in organic chemistry/important chemical reactions/ which you all studied in class 12 are defined as follows:

1. Sandmeyer reaction:

This is the reaction which is generally used for the preparation of aryl halides from aryl diazonium salt where aryl corresponds to the ring like structure. Sandmeyer reaction can also be called as a substitution reaction of any aromatic ring by introducing diazonium salt which is done through displacement reaction and copper is used as a catalyst in this reaction. Reaction can be shown as follows:

$C:\Users\Dr.Swati Kashyap\OneDrive\Desktop\Sandmeyer.png$

Here X represents halogen which can be chlorine, bromine, iodine, etc, or maybe a cyanide ion.

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2. Gattermann reaction:

Gattermann reaction is also known by the method of formylation of those compounds which have aromatic ring. It is very similar with Friedel-crafts reaction. This reaction is generally used for obtaining chloro or bromo benzene from bromobenzene diazonium chloride by reacting with Cu/HCl or Cu/HBr respectively and the reaction can be represented as:

$C:\Users\Dr.Swati Kashyap\OneDrive\Desktop\Gaterman.png$

3. Balz-Schiemann reaction:

This reaction is used for preparing aryl fluoride this can be done by number of steps like first arene-diazonium chloride is prepared with the help of fluoroboric acid then arene diazonium fluoroborate which is precipitated and decomposes further which produces aryl halide with the help of heating. Reaction can be shown as:

$C:\Users\Dr.Swati Kashyap\OneDrive\Desktop\BS reaction.png$

4. Finkelstein reaction:

This reaction is mainly prepared for preparing alkyl iodides which can be proceed by the reaction between alkyl chlorides with sodium iodide represented by the chemical formula NaI in the presence of dry acetone and reaction can be shown as below:

Here X represents halogen which can be chlorine, bromine, iodine etc.

5. Swarts reaction:

This is the reaction which gives alkyl fluoride as a product when alkyl chloride is heated in the presence of metallic fluoride compounds which can be represented as and this further give alkyl fluorides. Reaction can be shown as:

Here X represents halogen which can be chlorine, bromine, iodine etc.

6. Wurtz reaction:

This reaction is generally used for the production of hydrocarbons in which alkyl halides generally react with sodium and dry ether in this we get double number of carbon atom which we have in reactant side and the reaction can be shown as follows:

This reaction is proceed in the presence of dry acetone.

7. Wurtz-Fitting reaction:

This reaction is one of the most basic and important reaction for getting alkyl arene. In this reaction alkyl halide or aryl halide reacts with sodium in the availability of dry ether and reaction can be represented as:

$C:\Users\Dr.Swati Kashyap\OneDrive\Desktop\12.png$

8. Fitting reaction:

This is one of the reaction in which two aryl groups get joined with each other and we can define the reaction in such a way that aryl halides when react with sodium in dry ether which give analogous compounds in which two aryl groups are joined with each other. Reaction can be shown as:

$C:\Users\Dr.Swati Kashyap\OneDrive\Desktop\1.png$

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9. Friedel-Crafts Alkylation reaction:

In this reaction benzene is prepared with the help of an alkyl halide in the presence of anhydrous aluminum chloride represented by the chemical formula AlCl₃ which further gives the alkyl benzene as a product and the reaction can be shown as:

$C:\Users\Dr.Swati Kashyap\OneDrive\Desktop\2.png$

10. Frieldel-Crafts Acylation reaction:

Friedel craft acylation is same like friedel craft alkylation the difference is in this acyl halide is reacted with benzene but in alkyl halide alkyl halide is reacted with benzene but both the reactions takes place in presence of anhydrous aluminum chloride and the reaction can be shown as:

$C:\Users\Dr.Swati Kashyap\OneDrive\Desktop\123.png$

11. Riemaer-Tiemann Reaction:

This is a multistep reaction in which salicylaldehyde is the product of this reaction which can be shown and explained as follows:

$C:\Users\Dr.Swati Kashyap\OneDrive\Desktop\CH.png$

In step phenol is reacted with chloroform and sodium hydroxide and form an intermediate compound and further this reacts with sodium hydroxide in which aldehyde group is present at ortho position which on heating give salicyladehyde.

NCERT Chemistry Notes:

12. Kolbe’s reaction:

In presence of sodium hydroxide phenol gives sodium phenoxide which further gets reacted with carbon dioxide in acidic medium and produce hydroxybenzoic acid as a product and the reaction can be shown as:

$C:\Users\Dr.Swati Kashyap\OneDrive\Desktop\1.png$

13. Rosenmund reaction:

This reaction is generally proceed in the presence of catalyst which is known by the name of rosenmund catalyst which either be in the form of palladium or barium sulfate represented by PdSO₄ or BaSO₄. In this reaction benzoyl chloride undergoes through hydrogenation process and produce benzeldehyde in the presence of rosenmund catalyst and reaction can be shown as:

$C:\Users\Dr.Swati Kashyap\OneDrive\Desktop\12.png$

14. Gattermann Koch reaction:

This reaction is also produce benzaldehyde in which benzene reacts with carbon monoxide and hydrochloric acid in the availability of aluminium chloride and gives benzaldehyde as a product which can be shown as:

$C:\Users\Dr.Swati Kashyap\OneDrive\Desktop\1.png$

15. Sabatier-Sanderson reaction

: In this reaction hydrogenation process occurs i.e. addition of hydrogen atoms and this reaction converts alkene into alkanes. This is one of main reaction by which ethane is prepared at large scale in this ethylene or ethane undergoes through the process of hydrogenation in the presence of catalyst Ni and gives ethane. The reaction can be represented as:

$C:\Users\Dr.Swati Kashyap\OneDrive\Desktop\12.png$

16. Houben-Hoesch reaction

: This is one of the important reaction which provide acyl chlorides as their product this is very similar with friedel craft alkylation and friedel craft acylation as we discussed above in this reaction phenol reacts with zinc chloride and cyanide group which further produces more than one acyl group in the product and the reaction can be shown as:

$C:\Users\Dr.Swati Kashyap\OneDrive\Desktop\A.png$

17. Carbylamine reaction:

This is the reaction which is used to produce isocyanides or carbylamines as a product that’s why they are named as carbylamines reaction. Aliphatic and aromatic amines are heated in the presence of chloroform and ethanolic potassium hydroxide and produce isocyanides during this reaction

Other than these reaction many other reactions are also known to us which are aldol condensation, cross aldol condensation, gattermann Koch synthesis, Hoffmann bromaamide reaction, HVZ reaction, Fehling test, Tollen’s reagent test etc.

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Frequently Asked Question (FAQs)

1. What do you mean by balanced chemical reaction?

Balanced chemical reaction refers to those reaction in which number of components present in reactant side and product side are exactly equal like if there are 3 carbon atoms and 2 oxygen atoms are there in reactant side then exactly 3 carbon atom and 2 oxygen atoms should be present in product side.

2. What is the full form of HVZ reaction?

Hell Volhard Zelinsky reaction.

3. Define tollen’s test.

Tollen’s test is basically known by the name silver mirror test in which when aldehyde gets treated with freshly prepared ammoniacal silver nitrate then it produce a mirror i.e. a bright silver mirror which represents the formation of a silver mirror.

4. Which color precipitate will occur in Fehling reagent test?

When an aldehyde is heated with fehling solution then it produces reddish brown color precipitates.

5. Define aldol reaction.

Aldol reaction is done by those aldehydes and ketones which have one alpha hydrogen and it goes through the reaction in the presence of dilute alkali which acts as a catalyst and produce beta hydroxy aldehydes and beta hydroxyl ketones.