Organic chemistry is an integral part of the class 12 syllabus. If you prepare well, you could easily score more than 90% in reactions in organic chemistry class 12. There are students who, even though they love physical chemistry, feel overwhelmed when it comes to organic chemistry. Here are some important chemical reactions class 12th organic chemistry.
Understanding the concept of each reaction makes it easier for you to remember and ace the exam. Students are always recommended to study each reaction, write and practice it, and solve papers to stay well prepared and not feel overwhelmed before exams.
When an alkyl halide is converted to a different alkyl halide after reacting with a metal halide salt, it is called the Finkelstein reaction. It is driven forward due to the poor solubility in acetone of the just-formed halide salt and is an equilibrium process.
In the reaction between dry ether, alkyl halide, and sodium, you get hydrocarbons that come with double carbon atoms in the halide. This reaction is commonly known as the Wurtz reaction.
Friedel-Crafts alkylation Reaction
An alkyl halide is used to prepare benzene in the presence of anhydrous aluminium chloride giving Alkylbenzene.
Friedel-Crafts acylation Reaction
You will get acyl benzene when you react benzene with an acyl halide in the presence of Lewis acids.
Reacting two moles of aryl halide along with two moles of Na while in the presence of dry ether, you will obtain biphenyl. It is the Fittig reaction.
Alkyl chloride, when heated under the presence of metallic fluoride, you will get alkyl fluorides.
Oxymercuration Demercuration Reaction
In this reaction, alkene reacts with Hg2 salt and an oxygen nucleophile. It forms an organomercury intermediate. The intermediate’s carbon-mercury bond then converts to a carbon-hydrogen bond by NaBH4 treatment. The whole reaction converts the alkene to alcohol when there is a nucleophile. Or to ether when the nucleophile is alcohol.
In this reaction, phenol reacts with sodium hydroxide giving sodium phenoxide. It again reacts with carbon dioxide in an acidic medium giving hydroxybenzoic acid.
The formation of aldehydes happens with the catalytic hydrogenation of acid chlorides.
Here direct oxidation of an aromatic or even heterocyclic bound methyl group happens with an aldehyde using chromyl chloride.
Here zinc amalgam reacts with aldehydes and ketones in concentrated hydrochloric acid, reducing the ketone or aldehyde to a hydrocarbon. This is considered to be a very powerful reduction method.
The aldehyde is heated using fresh prepared ammoniacal silver nitrate solution, giving you a bright silver mirror as it forms silver nitrate.
Here, aldol and also Ketol lose water, providing α, β unsaturated carbonyl compounds.
Aldehydes with the absence of alpha-hydrogen atoms undergo self-oxidation and reduction reaction while preparing it with concentrated alkali.
HVZ (Hell-Volhard-Zelinsky) Reaction
Α-hydrogen in carboxylic acids is halogenated at the α-position when treated with chlorine or bromine in the presence of a small amount of red phosphorus.
Here, primary amine warmed with alcoholic KOH and chloroform gives isocyanides. It is known as the carbylamine reaction and has a pretty offensive smell. The only primary amine can undergo this reaction which helps it differentiate from other classes of amines.
Gabriel phthalimide synthesis
It is prepared using Ethanolic Potassium Hydroxide and produces Phthalimide potassium salt when heated using Alkyl Halide following Alkaline hydrolysis forming corresponding primary amine.
This chemical reaction is used to synthesise aryl halides from aryl diazonium salts by using copper salts reagents or even as catalysts. This reaction is an example of radical nucleophilic aromatic substitution.
Benzene diazonium chloride reacts with phenol in which the phenol molecule located at the para position is mixed with diazonium salt giving p-hydroxyazobenzene.
When C6H5OH is treated with chloroform in the presence of NaOH, an aldehyde group is readily introduced at the benzene ring’s ortho position, creating o-hydroxybenzaldehyde.
Williamson Ether Synthesis
This is a very popular organic reaction where an alkyl halide and alcohol are converted to ether using a NaOH base.
When aryl cyanide or an alkyl dissolves in ether and is reduced with stannous chloride and HCl giving aromatic or aliphatic aldehydes. The reaction then proceeds to form aldimine hydrochloride, which is not stable and then hydrolyses, giving aldehydes.
Gattermann Koch Reaction
In this reaction, benzene and its derivative are made to react with carbon monoxide and hydrogen chloride in the presence of anhydrous AlCl3 or CuCl; this will give you substituted benzaldehyde or Benzaldehyde.
Wolff Kishner Reaction
Did you know you could convert ketones alongside aldehydes to hydrazine by reacting it with hydrazine? These “hydrazones” can again be converted to alkane by reacting with base and heat. The two reactions combine, forming the Wolff Kishner reaction.
When Fehling solution A and Fehling solution B are mixed by taking equal proportions, you will get a reddish-brown precipitate when you heat an aldehyde with the Fehling reagent.
In this electrolysis method or reaction, an aqueous solution of potassium or sodium salt of a carboxylic acid is taken, which gives alkane containing an even number of carbon atoms on electrolysis.
Hoffmann Bromamide Degradation Reaction
When you treat a primary amine with alcoholic or aqueous NaOH or even KOH and also Bromine, it will give you a primary amine having one carbon atom less than what the original amine had.
This reaction converts aryl amines to aryl fluorides through the diazotisation and subsequent thermal decomposition of the derived hexafluorophosphate or tetrafluoroborates. You can even induce this decomposition photochemically.
This reaction is quite similar to the Sandmeyer reaction, and the only major difference would be in this one, copper power is used in the presence of HCl/HBr, whereas in Sandmeyer, one uses Cu2Cl2/Cu2Br2 as a catalyst.
These are some of the major organic chemistry reactions you would come across when in class 12. While the base of the students in organic chemistry starts from class 11 or before, these reactions are considered among the most vital ones.