Compounds that contain carbon in their molecule in solid, liquid or gaseous state are called Organic Compounds. For Example, Nitrogen is an important class of organic compounds. The important classes of organic compounds containing nitrogen as a part of the functional group is called the Amines.

Amines are a significant class of chemical substances. Amine research is fascinating in a variety of ways. In biology, amino acid chemistry is crucial. It is necessary for all living things. We’ll look at the structure of amino acids and their physical characteristics in this section.

Class of Compounds	General Formula
Primary Amine	RNH2
Secondary Amine	R2NH
Tertiary Amine	R3N

Table of Contents

What are Amines?

Amines are regarded as derivatives of ammonia in which one, two or all three hydrogen atoms are replaced by an alkyl or aryl group.

NH₃ ⇢ RNH₂ ⇢ R₂NH ⇢ R₃N

Amines have a lone pair of electrons on the nitrogen atom. They are essentially ammonia derivatives. In Ammonia, substituent groups such as alkyl or aryl replace one or more hydrogen atoms, resulting in a new family of organic molecules known as Amines. Amino acids, biogenic amine, trimethylamine, and aniline are examples of important amine structures.

Amines constitute an important class of Organic compounds. Synthetic examples include polymers, drugs etc. For example, quinine is an important anti-malarial drug, adrenaline and ephedrine are used for increasing blood pressure, codeine is used as an analgesic, Benadryl is used as an antihistamine drug.

Structure of Amines

Amines are the derivatives of ammonia in which one or more hydrogen atoms has been replaced by alkyl groups. Hence, the structures of amines are similar to ammonia. In ammonia, nitrogen atoms undergo sp³  hybridization forming four sp³ hybrid orbitals. Three of these sp³ hybrid orbitals overlapped with s-orbital of H forms three N—H bonds and the fourth sp³ hybrid orbitals contain a lone pair of electrons.

Examples are Amino acids, biogenic amine, trimethylamine and aniline.

Classification of Amines

The Amines are classified as :

• Primary (1°): Primary amines are those amines if one hydrogen atom of ammonia is replaced by alkyl (R), such amine is called primary amine, which has the general formula: RNH₂.
• Secondary (2°): Secondary amine is that amine if two hydrogen atoms of ammonia or one H atom of  RNH₂ is replaced by another alkyl (R’) is called the Secondary amine with the general formula: R—NH—R’.
• Tertiary (3°): Tertiary amine is that amine if we replace all the three H atoms of ammonia or another H atom of R—NH—R’ by alkyl group (R”)  which gives R—N(R’)R”.

Amines are further classified into two categories:

1. Aliphatic Amines: Aliphatic Amines are those Amines in which the nitrogen atom is directly bonded to one or more alkyl groups. For example, CH₃NH₂  is a Methylamine (1°).
2. Aromatic Amines: Aromatic Amines are of two types-

• Aryl Amines: Aryl Amines are those amines in which the nitrogen atom is directly bonded to one or more which is the same or different aryl groups. Aromatic amines are called arylamines. For example,

• Arylalkyl amines: Those amines in which the nitrogen atom is bonded to the side chain of the aromatic ring is called aryl alkyl amines. This is also called a side chain substituted amines. For example,

Physical properties of Amines

The important physical properties of amines are:

• Physical state and smell: Lower members of the aliphatic amines family such as methylamine, dimethylamine are gases at ordinary temperature and have smelled like ammonia. The higher members with three or more C atoms are mostly liquid has a fishy smell. Most of the amines have an unpleasant odour. Aromatic amines are toxic. Most of the amines in pure form are colourless but they are easily oxidised and they become coloured due to impurities.
• Boiling Points: Amines have higher boiling points than hydrocarbons of comparable molecular mass because amines are polar compounds and with the exception of tertiary amines form associate molecules due to intermolecular hydrogen bonding between nitrogen of one and hydrogen of another molecule as shown below:

Amines have lower boiling points than those of alcohols or carboxylic acids because the electronegativity of nitrogen is lower than that of oxygen and hence O-H bonds present in alcohols and carboxylic acids are more polar than N-H bonds in amines. The hydrogen bonds in alcohols and carboxylic acids are stronger and have higher boiling points. 

• Comparison of boiling points of different groups of compounds: 

Compound	Molar Mass	Boiling point (K)
Methanoic acid	46	374
Ethanol	46	351.5
Ethanamine	45	290
Propane	44	231

In Isomeric Amines, the intermolecular association is more in primary amines than in secondary amines. Tertiary amines do not have intermolecular associations due to the absence of hydrogen atoms available for hydrogen bond formation. Hence, primary and secondary amines have the highest boiling point whereas tertiary amines have the lowest boiling points.

Thus, the order of Boiling points of isomeric amines is: 

Primary>Secondary>Tertiary

Example:    CH₃CH₂CH₂NH_{2      >}  (C₂H₅)₂NH  > C₂H₅N(CH₃)₂

Propylamine (Primary)    >  Diethylamine (Secondary)  >  Ethyldimethylamine (Tertiary)

b.p. : 323 K                                    b.p. : 329.3 K                                     b.p. : 310.5 K

• Solubility: The lower aliphatic amines are soluble in water because they are capable of forming hydrogen bonds with water.  However, Solubility decreases with increases in the molar mass of amines due to an increase in the size of the hydrophobic alkyl part. The higher amines containing six or more carbon atoms are insoluble because of weaker hydrogen bonds the solubility of amines in water is less than that of alcohols. For example, butan-1-amine is less soluble than butan-1-ol. The amines are also soluble in less polar solvents like ether, alcohol etc.

Aromatic Amines are insoluble in water because larger hydrocarbon part tends to retard the formation of hydrogen bonds. It is quite soluble in organic solvents such as ether, alcohols. For example, Aniline is insoluble in water. 

• Melting Points: The melting points of aryl amines increases with an increase in the molecular mass of the compound.
• Toxic Nature: Aryl amines are highly toxic substances as these compounds can destroy red blood cells and lead to mental instability.

Sample Questions (FAQs)

Question 1: Why does methylamine have a lower boiling point than methanol?

Answer: 

Methylamine has a lower boiling point than methanol because Methylamine is polar and form intermolecular hydrogen bonds and its tendency to form intermolecular hydrogen bonds is less than methanol which is a highly electronegative oxygen atom.

Question 2: Trimethylamine and n-propylamine have the same molecular mass, the former boils at a lower temperature (276 K) than the latter (322 K). Why?

Answer: 

As n-propylamine has two hydrogen atoms on nitrogen atoms and form intermolecular hydrogen bonding. Therefore, its boiling point is high whereas, trimethylamine does not have hydrogen atoms on the nitrogen atom and it do not undergo hydrogen bonding. Therefore, its boiling point is low.

Question 3: Explain Tertiary amines do not undergo acylation.

Answer: 

Acylation reactions are those amines containing replaceable hydrogen atoms that react with acid chloride to form substituted amides. In tertiary amines, there is no replaceable H atom. Hence, it does not react with acetyl chloride and does not undergo acylation.

Question 4: Arrange the following in the increasing order of boiling points C₂H₅NH_2, C₂H₅OH, (CH₃)₃N.

Answer: 

The increasing order of boiling points is  (CH₃)₃N < C₂H₅NH₂ < C₂H₅OH

Question 5: Why are amines insoluble in water?

Answer: 

Amines are insoluble in water because the large hydrocarbon part attached to it is hydrophobic and secondly it includes that hydrogen bonding does not occur and more hydrocarbons get attached to it and become more hydrophobic.

Question 6: Why do primary amines have lower solubility than alcohols?

Answer: 

Primary amines have lower solubility than alcohols because alcohols have high polarity as compared to amines.

Question 7: Is amine flammable?

Answer: 

No, the amine is not extremely flammable at room temperature and amines have high boiling liquids that are combustible.

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.

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CBSE Class 12 Chemistry Syllabus Download PDF

Below is the CBSE Class 12 Syllabus along with the marking scheme and time duration of the Chemistry exam.

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.

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.