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14 Most Important Reactions in Chemistry

Kolbe Reaction

The preparation of hydrocarbons at the anode by electrolysis of aqueous solutions of sodium or potessium salts of acids is called Kolbe synthesis and this reaction is called Kolbes reaction. Both types of hydrocarbons (saturated and unsaturated) can be obtained by this reaction.

Example

2CH3COONa CH3.CH3 + 2CO2 (Anode) | 2Na + 2H2O 2NaOH + H2 (Cathode)

Kolbe reaction

Wurtzs Reaction

This reaction is used in the synthesis of saturated hydrocarbons. is done in this reaction. In this reaction alkyl halide is treated with sodium metal in the presence of dry ether to form corresponding paraffin.

RX + 2Na + XR R – R + 2NaX

a) Methyl Iodide gives Ethane

CH3 I + 2Na + I CH3 CH3.CH3 + 2NaI

b) Ethyl Iodide gives n-butane

C2H5 I + 2Na + I C2H5 C4H10 + 2NaI

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Franklands Reaction

The formation of paraffin by the combination of two molecules alkyl halide in the presence of zinc metal is called Franklands reaction.

Example:-

R I + Zn + I R R – R + ZnI2

CH3 I + Zn + I CH3 CH3.CH3 + ZnI2

Chemistry Notes

Physics Notes

Biology Notes

Wurtz Fitting Reaction

The reaction of combining alkyl halide with aryl halide in dry ether in the presence of sodium to obtain aromatic hydrocarbon is called Wurtz fitting reaction.

Iodo reacts with benzene methyl iodide to form toluene.

C6H5 I + 2Na + I CH3 C6H5.CH3 + 2NaI

Same here,

C6H5 I + 2Na + I C2H5 C6H5.C2H5 + 2NaI

Friedel Crafts Reaction

When benzene or other aromatic hydrocarbon and an alkyl or acyl halide are treated in the presence of anhydrous AlCl3 (catalyst), the hydrogen atom of the benzene nucleus is replaced by an alkyl or acyl radical. This reaction is called Friedel Crafts reaction.

C6H6 + CH3Cl C6H5.CH3 + HCl

C6H6 + CH3COCl C6H5COCH3 + HCl

Cannizzaros Reaction

When aldehyde is treated with aqueous or alcoholic castic alkali solution, one molecule of aldehyde is reduced to alcohol and the other molecule gets oxidised to acid. This reaction gives only those aldehydes which do not have alpha hydrogen atom. This reaction is called Cannizzaros Reaction.

Example :-

2HCHO + NaOH CH3OH + HCOONa

2C6H5CHO + NaOH C6H5CH2OH + C6H5COONa

Carbylamine Reaction

When anylene and alcoholic KOH are heated with a few drops of chloroform, a strong odorous phenyl isocyanide is obtained. Alyphatic primary amine also gives this reaction. Read more

C6H5NH2 + CHCl3 + 3KOH C6H5NC + 3KCl + 3H2O

CH3NH2 + CHCl3 + 3KOH CH3NC + 3KCl + 3H2O

Aldol Condensation

Carbonil compounds having alpha hydrogen atom condense in the presence of NaOH, K2CO3 etc. Aceteldehyde condenses to form alcohol and this reaction is called aldol condensation.

Example :-

CH3CHO + HCH2CHO (2 Molecules) CH3CH(OH)CH2CHO

CH3CH2CHO + H.CH2CHO CH3CH2CH(OH)CH2CHO

Chemistry Notes

Physics Notes

Biology Notes

This condensation can occur in molecules of two similar or different aldehydes, in two similar or different ketones, and between an aldehyde and a ketone.

CH3CH2CHO + H.CH2CHO CH3CH2CH(OH)CH2CHO

Claisen Condensation

Condensation between two esters or between an ester and a ketone in the presence of sodium metal or C2H5ONa is called claisen condensation.