Amines are organic compounds formed by substituting an alkyl or aryl group for one or more hydrogen atoms in an ammonia (NH3) molecule. They can be found in nature in proteins, vitamins, alkaloids, and hormones. There are different methods of preparation of amines such as Nucleophilic Substitution Reaction, reduction of amides and nitriles, Hoffman arrangements.
In this article, we will learn in detail about preparation of amine along with their chemical reactions.
Table of Contents
Method of Preparation of Amines
There are different methods to prepare amines:
From Reduction of Nitro Compound
By passing hydrogen gas through a finely divided nickel, palladium, or platinum, as well as by reduction with metals in an acidic medium, nitro compounds are reduced to amines. Nitroalkanes can also be reduced to the corresponding alkanamines in the same way.
Reduction with iron scrap and hydrochloric acid is preferred because the FeCl2 formed during the reaction is hydrolyzed, releasing hydrochloric acid. As a result, only a trace of hydrochloric acid is required to initiate the reaction.
From Ammonolysis Alkyl Halide
The bond between carbon-halogen and alkyl or benzyl halides can be easily broken by a nucleophilic reaction. As a result, when an alkyl or benzyl halide reacts with an ethanolic solution of ammonia, a nucleophilic substitution reaction occurs in which the halogen atom is replaced by an amino (–NH2 ) group. Ammonolysis is the process by which an ammonia molecule cleaves the C–X bond. The reaction takes place in a sealed tube at 373 K. The resulting primary amine is a nucleophile and can react with an alkyl halide to form secondary and tertiary amines, and finally quaternary ammonium salt.
By treating the ammonium salt with a strong base, the free amine can be obtained:
Ammonolysis of alkyl halide has one disadvantage during the reaction it forms a mixture of primary, secondary, and tertiary amines and quaternary ammonium so to get Primary amine, as a major product we pass a large excess of ammonia.
From Reduction of Nitriles
Primary amines are formed when nitrites are reduced with lithium aluminum hydride (LiAlH4) or catalytically hydrogenated. This reaction is used to prepare amines with one more carbon atom than the starting amine, which is known as amine series ascent.
H2/Ni
R-CN ————————-> R-CH2-NH2
Na(Hg) /C2H5OH
From Reduction of Amide
When amides are reduced with lithium aluminum hydride, amines are formed.
(i) LiAlH4
R-CO-NH2 —————————–> R-CH2-NH2
(ii) H2O
From Gabriel Phthalimide Synthesis
Gabriel synthesis is a method for producing primary amines. When phthalimide is treated with ethanolic potassium hydroxide, it forms a potassium salt of phthalimide, which when heated with an alkyl halide and then alkaline hydrolyzed yields the corresponding primary amine. Gabriel’s phthalimide synthesis method does not produce aromatic primary amines because aryl halides do not undergo nucleophilic substitution reaction with the anion formed by phthalimide.
From Hoffmann Bromamide Degradation Reaction
Hoffmann developed a method for producing primary amines by treating an amide with bromine in an aqueous or ethanolic sodium hydroxide solution. An alkyl or aryl group migrates from the amide’s carbonyl carbon to the nitrogen atom during this degradation reaction. The amine thus formed has one fewer carbon atom than the amide.
Reductive animation of aldehydes and ketones produces 1°, 2°, and 3° amine. This reaction takes place in 2 step first is nucleophilic addition which gives imine and the second step is the reduction of imine which produce amine.
Curtius Reaction
Curtius reaction is also called Curtius rearrangement. In this reaction decomposition of acyl azide takes place which forms isocyanate. Isocyanate is unstable which on hydrolysis gives amine.
Schmidt Reaction
In Schmidt, reaction amines can be prepared with azide and a carboxylic acid.
Sample Problems on Preparation of Amines
Question 1: What are primary, secondary, andtertiary amines? give examples.
Answer:
One hydrogen atom of NH3 is replaced with an alkyl or aryl group in primary or 1° amine. Two hydrogen atoms of NH3 are replaced with an alky or aryl group in secondary or 2° amine. Three hydrogen atoms of NH3 are replaced with an alkyl or aryl group in tertiary amine.
Question 3: What happens when nitrobenzene is reduced? Write the chemical equation of the reaction.
Answer:
Reduction of nitro benzene gives aniline as final product. Chemical equation-
Question 4: What is the method to prepare ethylamine in the lab?
Answer:
Hofmann’s bromide reaction is used In the laboratory, we can make ethylamine using Hofmann’s bromide reaction. Bromine and potassium hydroxide solution are used to heat the propionamide.
Question 5: Which is more soluble in water primary amine or tertiary amines give a reason?
Answer:
Tertiary amines are more soluble in water because primary amines can form hydrogen bonds with water but tertiary amines cannot, primary amines are less soluble.
Neeraj Anand, Param Anand
Er. Neeraj K.Anand is a freelance mentor and writer who specializes in Engineering & Science subjects. Neeraj Anand received a B.Tech degree in Electronics and Communication Engineering from N.I.T Warangal & M.Tech Post Graduation from IETE, New Delhi. He has over 30 years of teaching experience and serves as the Head of Department of ANAND CLASSES. He concentrated all his energy and experiences in academics and subsequently grew up as one of the best mentors in the country for students aspiring for success in competitive examinations.
In parallel, he started a Technical Publication "ANAND TECHNICAL PUBLISHERS" in 2002 and Educational Newspaper "NATIONAL EDUCATION NEWS" in 2014 at Jalandhar. Now he is a Director of leading publication "ANAND TECHNICAL PUBLISHERS", "ANAND CLASSES" and "NATIONAL EDUCATION NEWS".
He has published more than hundred books in the field of Physics, Mathematics, Computers and Information Technology. Besides this he has written many books to help students prepare for IIT-JEE and AIPMT entrance exams. He is an executive member of the IEEE (Institute of Electrical & Electronics Engineers. USA) and honorary member of many Indian scientific societies such as Institution of Electronics & Telecommunication Engineers, Aeronautical Society of India, Bioinformatics Institute of India, Institution of Engineers. He has got award from American Biographical Institute Board of International Research in the year 2005.
Below is the CBSE Class 12 Syllabus along with the marking scheme and time duration of the Chemistry exam.
S.No
Title
No. of Periods
Marks
1
Solutions
10
7
2
Electrochemistry
12
9
3
Chemical Kinetics
10
7
4
d -and f -Block Elements
12
7
5
Coordination Compounds
12
7
6
Haloalkanes and Haloarenes
10
6
7
Alcohols, Phenols and Ethers
10
6
8
Aldehydes, Ketones and Carboxylic Acids
10
8
9
Amines
10
6
10
Biomolecules
12
7
Total
70
CBSE Class 12 Chemistry Practical Syllabus along with Marking Scheme
The following is a breakdown of the marks for practical, project work, class records, and viva. The total number of marks for all parts is 15. The marks for both terms are provided in the table below.
Evaluation Scheme for Examination
Marks
Volumetric Analysis
08
Salt Analysis
08
Content-Based Experiment
06
Project Work and Viva
04
Class record and Viva
04
Total
30
CBSE Class 12 Chemistry Syllabus (Chapter-wise)
Unit -1: Solutions
Raoult's law.
Colligative properties - relative lowering of vapour pressure, elevation of boiling point, depression of freezing point, osmotic pressure, determination of molecular masses using colligative properties, abnormal molecular mass.
Solutions, Types of solutions, expression of concentration of solutions of solids in liquids, solubility of gases in liquids, solid solutions.
Van't Hoff factor.
Unit -2: Electrochemistry
Redox reactions, EMF of a cell, standard electrode potential
Nernst equation and its application to chemical cells
Relation between Gibbs energy change and EMF of a cell
Kohlrausch's Law
Electrolysis and law of electrolysis (elementary idea)
Dry cell-electrolytic cells and Galvanic cells
Conductance in electrolytic solutions, specific and molar conductivity, variations of conductivity with concentration.
Lead accumulator
Fuel cells
Unit -3: Chemical Kinetics
Rate of a reaction (Average and instantaneous)
Rate law and specific rate constant
Integrated rate equations and half-life (only for zerfirst-order order reactions)
Concept of collision theory (elementary idea, no mathematical treatment)
Factors affecting rate of reaction: concentration, temperature, catalyst;
Order and molecularity of a reaction
Activation energy
Arrhenius equation
Unit -4: d and f Block Elements
Lanthanoids- Electronic configuration, oxidation states, chemical reactivity and lanthanoid contraction and its consequences.
Actinoids- Electronic configuration, oxidation states and comparison with lanthanoids.
General introduction, electronic configuration, occurrence and characteristics of transition metals, general trends in properties of the first-row transition metals – metallic character, ionization enthalpy, oxidation states, ionic radii, color, catalytic property, magnetic properties, interstitial compounds, alloy formation, preparation and properties of K2Cr2O7 and KMnO4.
Unit -5: Coordination Compounds
Coordination compounds - Introduction, ligands, coordination number, color, magnetic properties and shapes
The importance of coordination compounds (in qualitative analysis, extraction of metals and biological system).
IUPAC nomenclature of mononuclear coordination compounds.
Bonding
Werner's theory, VBT, and CFT; structure and stereoisomerism
Unit -6: Haloalkanes and Haloarenes
Haloarenes: Nature of C–X bond, substitution reactions (Directive influence of halogen in monosubstituted compounds only). Uses and environmental effects of - dichloromethane, trichloro methane, tetrachloromethane, iodoform, freons, DDT.
Haloalkanes: Nomenclature, nature of C–X bond, physical and chemical properties, optical rotation mechanism of substitution reactions.
Unit -7: Alcohols, Phenols and Ethers
Phenols: Nomenclature, methods of preparation, physical and chemical properties, acidic nature of phenol, electrophilic substitution reactions, uses of phenols.
Ethers: Nomenclature, methods of preparation, physical and chemical properties, uses.
Alcohols: Nomenclature, methods of preparation, physical and chemical properties (of primary alcohols only), identification of primary, secondary and tertiary alcohols, mechanism of dehydration, and uses with special reference to methanol and ethanol.
Unit -8: Aldehydes, Ketones and Carboxylic Acids
Carboxylic Acids: Nomenclature, acidic nature, methods of preparation, physical and chemical properties; uses.
Aldehydes and Ketones: Nomenclature, nature of carbonyl group, methods of preparation, physical and chemical properties, mechanism of nucleophilic addition, the reactivity of alpha hydrogen in aldehydes, uses.
Unit -9: Amines
Diazonium salts: Preparation, chemical reactions and importance in synthetic organic chemistry.
Amines: Nomenclature, classification, structure, methods of preparation, physical and chemical properties, uses, and identification of primary, secondary and tertiary amines.
Unit -10: Biomolecules
Proteins -Elementary idea of - amino acids, peptide bond, polypeptides, proteins, structure of proteins - primary, secondary, tertiary structure and quaternary structures (qualitative idea only), denaturation of proteins; enzymes. Hormones - Elementary idea excluding structure.
Vitamins - Classification and functions.
Carbohydrates - Classification (aldoses and ketoses), monosaccharides (glucose and fructose), D-L configuration oligosaccharides (sucrose, lactose, maltose), polysaccharides (starch, cellulose, glycogen); Importance of carbohydrates.
Nucleic Acids: DNA and RNA.
The syllabus is divided into three parts: Part A, Part B, and Part C. Part A consist of Basic Concepts of Chemistry, which covers topics such as atomic structure, chemical bonding, states of matter, and thermochemistry. Part B consists of Topics in Physical Chemistry, which includes topics such as chemical kinetics, equilibrium, and electrochemistry. Part C consists of Topics in Organic Chemistry, which covers topics such as alkanes, alkenes, alkynes, and aromatic compounds.
Basic Concepts of Chemistry:
Atomic structure: This section covers the fundamental concepts of atomic structure, including the electronic configuration of atoms, the Bohr model of the atom, and the wave nature of matter.
Chemical bonding: This section covers the different types of chemical bonds, including ionic, covalent, and metallic bonds, as well as the concept of hybridization.
States of the matter: This section covers the three states of matter - solid, liquid, and gas - and the factors that influence their properties.
Thermochemistry: This section covers the principles of thermochemistry, including the laws of thermodynamics and the concept of enthalpy.
Chapters in Physical Chemistry:
Chemical kinetics: This section covers the study of the rate of chemical reactions and the factors that influence it, including the concentration of reactants, temperature, and the presence of catalysts.
Equilibrium: This section covers the principles of chemical equilibrium, including the concept of Le Chatelier's principle and the equilibrium constant.
Electrochemistry: This section covers the principles of electrochemistry, including the concept of half-cell reactions, galvanic cells, and electrolysis.
Chapters in Organic Chemistry:
Alkanes: This section covers the properties and reactions of alkanes, including their structure, isomerism, and combustion.
Alkenes: This section covers the properties and reactions of alkenes, including their structure, isomerism, and addition reactions.
Alkynes: This section covers the properties and reactions of alkynes, including their structure, isomerism, and addition reactions.
Aromatic compounds: This section covers the properties and reactions of aromatic compounds, including their structure, isomerism, and electrophilic substitution reactions.
In addition to the topics covered in the syllabus, the CBSE Class 12 Chemistry exam also tests students on their analytical and problem-solving skills, as well as their ability to apply the concepts learned in the classroom to real-world situations.
Students can also check out the Tips for the Class 12 Chemistry Exam. They can easily access the Class 12 study material in one place by visiting the CBSE Class 12 page at ANAND CLASSES (A School Of Competitions). Moreover, to get interactive lessons and study videos, download the ANAND CLASSES (A School Of Competitions) App.
Frequently Asked Questions on CBSE Class 12 Chemistry Syllabus
Q1
How many chapters are there in the CBSE Class 12 Chemistry as per the syllabus?
There are 10 chapters in the CBSE Class 12 Chemistry as per Syllabus. Students can learn all these chapters efficiently using the study materials provided at ANAND CLASSES (A School Of Competitions).
Q2
What is the marking scheme for CBSE Class 12 Chemistry practical exam according to the syllabus?
The marking scheme for CBSE Class 12 Chemistry practical exam, according to the syllabus, is 8 marks for volumetric analysis, 8 marks for salt analysis, 6 marks for the content-based experiment, 4 marks for the project and viva and 4 marks for class record and viva.
Q3
Which is the scoring chapter in Chemistry as per CBSE Class 12 syllabus?
The chapter Electrochemistry in Chemistry is the scoring chapter as per CBSE Class 12 syllabus.
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