Isomerism refers to the phenomenon where two or more compounds have the same molecular formula but different structural arrangements or spatial orientations, resulting in distinct chemical properties. These compounds with the same formula but different structures are called isomers.

Isomerism – Definition, Types, Structure, Examples, and FAQs

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Isomerism refers to the phenomenon where two or more compounds have the same molecular formula but different structural arrangements or spatial orientations, resulting in distinct chemical properties. These compounds with the same formula but different structures are called isomers.

Isomerism Definition

Isomerism is a chemical phenomenon where two or more compounds have the same molecular formula but different structural arrangements or spatial orientations, resulting in distinct chemical or physical properties.

Isomerism Types

Isomerism can be classified into two categories as follows:

  • Structural or constitutional isomerism
  • Stereoisomerism

Structural Isomerism

Structural isomerism is a type of isomerism where two or more compounds with the same molecular formula have different connectivity or arrangements of atoms in their chemical structures. It is also known as constitutional isomerism.

Because they have the same molecular formula, ethanol, and dimethyl ether are isomers. C2H6O. Because the atoms in each chemical are bonded differently, they are structural isomers.

The following are some examples of structural isomerism in various forms:

  • Chain isomerism
  • Position isomerism
  • Functional isomerism
  • Metamerism
  • Tautomerism
  • Ring chain isomerism

Chain Isomerism

Chain isomers are isomeric substances that differ solely in the arrangement of carbon atoms in the base chain, and chain isomerism is isomerism between them. The carbon atom chain or skeleton differs amongst isomers of this type. 

Carbon atoms can be arranged in a straight or branched chain. Chain isomerism does not exist in molecules comprising up to three carbon atoms since they are a continuous chain with no chance of branching. It is demonstrated for compounds with four or more carbon atoms. 

  • Chain isomerism in alkanes: Alkanes containing four or more carbon atoms. For example, Two chain isomers are represented by the chemical formula C4H10.
Isomerism refers to the phenomenon where two or more compounds have the same molecular formula but different structural arrangements or spatial orientations, resulting in distinct chemical properties. These compounds with the same formula but different structures are called isomers.
  • Chain isomerism in alkenes: When writing chain isomers for alkenes, the position of the double bond should not be modified. For example, Two chain isomers are represented by the chemical formula C4H8.
Isomerism refers to the phenomenon where two or more compounds have the same molecular formula but different structural arrangements or spatial orientations, resulting in distinct chemical properties. These compounds with the same formula but different structures are called isomers.
  • Chain isomerism in alkynes: Chain isomerism occurs in alkynes, which are compounds having five or more carbon atoms. The two chain isomers are represented by the chemical formula C5H8.
Isomerism refers to the phenomenon where two or more compounds have the same molecular formula but different structural arrangements or spatial orientations, resulting in distinct chemical properties. These compounds with the same formula but different structures are called isomers.

Position Isomerism

Position isomerization is a phenomenon that occurs when two or more compounds differ in the position of a component atom or functional group on the carbon skeleton.

C3H8O, for example, is made up of two alcohols:

Isomerism refers to the phenomenon where two or more compounds have the same molecular formula but different structural arrangements or spatial orientations, resulting in distinct chemical properties. These compounds with the same formula but different structures are called isomers.

Functional Isomerism

Two or more molecules with the same chemical formula but distinct functional groups are called functional isomers. Functional isomerism is the term for this occurrence. 

For example, the chemical formula C3H6O denotes both an aldehyde and a ketone:

Isomerism refers to the phenomenon where two or more compounds have the same molecular formula but different structural arrangements or spatial orientations, resulting in distinct chemical properties. These compounds with the same formula but different structures are called isomers.

Metamerism

Metamers are molecules that have the same chemical formula but differ in atomic or group locations on both sides of bridge functional groups. They are distinguished by the nature of the alkyl groups surrounding a certain functional group. 

As a result, they have a connection. For example, the chemical formula C4H10O accommodates three metameric isomeric ethers.

Isomerism refers to the phenomenon where two or more compounds have the same molecular formula but different structural arrangements or spatial orientations, resulting in distinct chemical properties. These compounds with the same formula but different structures are called isomers.

Tautomerism

Tautomers are functional isomers that exist in dynamic equilibrium at the same time. The most prevalent kind is keto-enol tautomerism, which is caused by the 1,3 movement of the hydrogen atom from carbon to oxygen and vice versa.

For example,

Isomerism refers to the phenomenon where two or more compounds have the same molecular formula but different structural arrangements or spatial orientations, resulting in distinct chemical properties. These compounds with the same formula but different structures are called isomers.

Tautomerism in an aldehyde or ketone requires the existence of a – hydrogen, which is involved in 1,3 – migration. In the lack of a – hydrogen, tautomerism is absent. Acetone, acetaldehyde, and acetophenone, for example, might display tautomerism due to the existence of a—hydrogen, whereas benzaldehyde and benzophenone do not due to the absence of a – hydrogen.

Isomerism refers to the phenomenon where two or more compounds have the same molecular formula but different structural arrangements or spatial orientations, resulting in distinct chemical properties. These compounds with the same formula but different structures are called isomers.

Ring-chain Isomerism

Ring chain isomerism is structural isomerism that differs from the other structural isomers discussed previously. It is present in isomeric open-chain and cyclic molecules. Compounds with the same chemical formula but open-chain or cyclic structures are known as ring chain isomers. And this phenomenon is known as ring chain isomerism.

The ring chain isomers are represented by the chemical formula C3H6.

Isomerism refers to the phenomenon where two or more compounds have the same molecular formula but different structural arrangements or spatial orientations, resulting in distinct chemical properties. These compounds with the same formula but different structures are called isomers.

Stereoisomerism

Stereoisomers are compounds that have the same chemical and structural formulae but differ in the relative arrangement of the atoms or groups in space, a phenomenon known as stereoisomerism.

Stereoisomerism can be divided into two categories:

Conformational Isomers

Conformational isomers are stereoisomers having different relative positions of atoms inside the molecule that can be interconverted by rotating around sigma links. In other words, there is no need to break and re-make covalent bonds in order to interconvert these isomers.

Configurational Isomers

Stereoisomers that can only be interconverted by breaking and reconstructing covalent bonds rather than rotating around sigma bonds are known as configurational isomers. Geometrical isomerism and optical isomerism are the two types of configurational isomerism.

Geometrical Isomerism 

Isomerism generated by constrained rotation around a link in a molecule is known as geometrical and also called cis-trans isomerism. A wide range of substances exhibits geometrical isomerism, which can be characterized as follows:

  • C=C, C=N, and N=N are examples of compounds with double bonds.
  • A cyclic molecule, including homocyclic, heterocyclic, and fused ring systems.
  • Steric hindrance compounds prevent rotation around a single bond. Biphenyls, for example.
Isomerism refers to the phenomenon where two or more compounds have the same molecular formula but different structural arrangements or spatial orientations, resulting in distinct chemical properties. These compounds with the same formula but different structures are called isomers.

Optical Isomerism 

Certain chemicals can exist in two stereoisomeric forms that are incompatible with one another. These isomers have equal physical properties, such as melting point, boiling point, refractive index, density, solubility, and so on, despite the change in atom arrangement.

They are also similar in most of their chemical interactions. They only differ in their behaviour when it comes to plane polarised light; one rotates it to the right, while the other rotates it to the left, but to the same degree. An optical isomer is a pair of chemicals that have the same optical properties.

Optical isomers are two compounds that contain the same number and type of atoms, bonds, and spatial configurations of the atoms but are not superimposable mirror images of each other. Enantiomers are isomers that are non-superimposable mirror reflections of each other.

Isomerism refers to the phenomenon where two or more compounds have the same molecular formula but different structural arrangements or spatial orientations, resulting in distinct chemical properties. These compounds with the same formula but different structures are called isomers.

FAQs on Isomerism

What is Isomerism?

Two or more compounds with the same molecular formula but distinct physical and chemical properties are known as isomers. Isomerism is the term for this phenomenon.

What are the Types of Isomerism?

Isomerism can be divided into two categories. Stereoisomerism and structural isomerism are the two types.

  • Structural isomerism
    1. Chain isomerism
    2. Positional isomerism
    3. Functional isomerism
    4. Metamerism
    5. Tautomerism
    6. Ring chain isomerism
  • Stereoisomerism
    1. Constitutional isomerism
    2. Conformational isomerism
      • Optical isomerism
      • Geometrical isomerism

What is Ring Chain Isomerism?

Compounds with the same chemical formula but open-chain or cyclic structures are known as ring chain isomers. Ring-chain isomerism is the term for this phenomena.

For example,  the molecular formula C3H6 represents the ring chain isomers

Isomerism refers to the phenomenon where two or more compounds have the same molecular formula but different structural arrangements or spatial orientations, resulting in distinct chemical properties. These compounds with the same formula but different structures are called isomers.

What is Chiral Carbon?

The carbon atom, which is attached to four different functional groups or molecules, is known as chiral carbon.

What is Structural Isomerism?

The structural isomers or constitutional isomers differ in the connection of their atoms, and this phenomenon is known as constitutional isomerism. There are six types of structural isomerism.

  1. Chain isomerism
  2. Positional isomerism
  3. Functional isomerism
  4. Metamerism
  5. Tautomerism
  6. Ring chain isomerism

What is Positional isomerism?

Position isomers are two or more compounds that differ in the position of a constituent atom or functional group on the carbon skeleton, and the phenomenon is known as position.

 For example,C3H8O, represents two alcohols:

Isomerism refers to the phenomenon where two or more compounds have the same molecular formula but different structural arrangements or spatial orientations, resulting in distinct chemical properties. These compounds with the same formula but different structures are called isomers.

Which type of Isomerism is possible in CH3CH=CHCH3?

H3C-CH=CH-CH3 and H2C=CH-CH2-CH3 are the possible structure of the given compound, and as the position of double bond is different in both the structures. Thus, CH3CH=CHCH3 has Positional Isomerism.

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 11 Chemistry Syllabus

CBSE Class 11 Chemistry Syllabus is a vast which needs a clear understanding of the concepts and topics. Knowing CBSE Class 11 Chemistry syllabus helps students to understand the course structure of Chemistry.

Unit-wise CBSE Class 11 Syllabus for Chemistry

Below is a list of detailed information on each unit for Class 11 Students.

UNIT I – Some Basic Concepts of Chemistry

General Introduction: Importance and scope of Chemistry.

Nature of matter, laws of chemical combination, Dalton’s atomic theory: concept of elements,
atoms and molecules.

Atomic and molecular masses, mole concept and molar mass, percentage composition, empirical and molecular formula, chemical reactions, stoichiometry and calculations based on stoichiometry.

UNIT II – Structure of Atom

Discovery of Electron, Proton and Neutron, atomic number, isotopes and isobars. Thomson’s model and its limitations. Rutherford’s model and its limitations, Bohr’s model and its limitations, concept of shells and subshells, dual nature of matter and light, de Broglie’s relationship, Heisenberg uncertainty principle, concept of orbitals, quantum numbers, shapes of s, p and d orbitals, rules for filling electrons in orbitals – Aufbau principle, Pauli’s exclusion principle and Hund’s rule, electronic configuration of atoms, stability of half-filled and completely filled orbitals.

UNIT III – Classification of Elements and Periodicity in Properties

Significance of classification, brief history of the development of periodic table, modern periodic law and the present form of periodic table, periodic trends in properties of elements -atomic radii, ionic radii, inert gas radii, Ionization enthalpy, electron gain enthalpy, electronegativity, valency. Nomenclature of elements with atomic number greater than 100.

UNIT IV – Chemical Bonding and Molecular Structure

Valence electrons, ionic bond, covalent bond, bond parameters, Lewis structure, polar character of covalent bond, covalent character of ionic bond, valence bond theory, resonance, geometry of covalent molecules, VSEPR theory, concept of hybridization, involving s, p and d orbitals and shapes of some simple molecules, molecular orbital theory of homonuclear diatomic molecules(qualitative idea only), Hydrogen bond.

UNIT V – Chemical Thermodynamics

Concepts of System and types of systems, surroundings, work, heat, energy, extensive and intensive properties, state functions. First law of thermodynamics – internal energy and enthalpy, measurement of U and H, Hess’s law of constant heat summation, enthalpy of bond dissociation, combustion, formation, atomization, sublimation, phase transition, ionization, solution and dilution. Second law of Thermodynamics (brief introduction)
Introduction of entropy as a state function, Gibb’s energy change for spontaneous and nonspontaneous processes.
Third law of thermodynamics (brief introduction).

UNIT VI – Equilibrium

Equilibrium in physical and chemical processes, dynamic nature of equilibrium, law of mass action, equilibrium constant, factors affecting equilibrium – Le Chatelier’s principle, ionic equilibrium- ionization of acids and bases, strong and weak electrolytes, degree of ionization,
ionization of poly basic acids, acid strength, concept of pH, hydrolysis of salts (elementary idea), buffer solution, Henderson Equation, solubility product, common ion effect (with illustrative examples).

UNIT VII – Redox Reactions

Concept of oxidation and reduction, redox reactions, oxidation number, balancing redox reactions, in terms of loss and gain of electrons and change in oxidation number, applications of redox reactions.

UNIT VIII – Organic Chemistry: Some basic Principles and Techniques

General introduction, classification and IUPAC nomenclature of organic compounds. Electronic displacements in a covalent bond: inductive effect, electromeric effect, resonance and hyper conjugation. Homolytic and heterolytic fission of a covalent bond: free radicals, carbocations, carbanions, electrophiles and nucleophiles, types of organic reactions.

UNIT IX – Hydrocarbons

Classification of Hydrocarbons
Aliphatic Hydrocarbons:
Alkanes – Nomenclature, isomerism, conformation (ethane only), physical properties, chemical reactions.
Alkenes – Nomenclature, structure of double bond (ethene), geometrical isomerism, physical properties, methods of preparation, chemical reactions: addition of hydrogen, halogen, water, hydrogen halides (Markovnikov’s addition and peroxide effect), ozonolysis, oxidation, mechanism of electrophilic addition.
Alkynes – Nomenclature, structure of triple bond (ethyne), physical properties, methods of preparation, chemical reactions: acidic character of alkynes, addition reaction of – hydrogen, halogens, hydrogen halides and water.

Aromatic Hydrocarbons:

Introduction, IUPAC nomenclature, benzene: resonance, aromaticity, chemical properties: mechanism of electrophilic substitution. Nitration, sulphonation, halogenation, Friedel Craft’s alkylation and acylation, directive influence of functional group in monosubstituted benzene. Carcinogenicity and toxicity.

To know the CBSE Syllabus for all the classes from 1 to 12, visit the Syllabus page of CBSE. Meanwhile, to get the Practical Syllabus of Class 11 Chemistry, read on to find out more about the syllabus and related information in this page.

CBSE Class 11 Chemistry Practical Syllabus with Marking Scheme

In Chemistry subject, practical also plays a vital role in improving their academic scores in the subject. The overall weightage of Chemistry practical mentioned in the CBSE Class 11 Chemistry syllabus is 30 marks. So, students must try their best to score well in practicals along with theory. It will help in increasing their overall academic score.

CBSE Class 11 Chemistry Practical Syllabus

The experiments will be conducted under the supervision of subject teacher. CBSE Chemistry Practicals is for 30 marks. This contribute to the overall practical marks for the subject.

The table below consists of evaluation scheme of practical exams.

Evaluation SchemeMarks
Volumetric Analysis08
Salt Analysis08
Content Based Experiment06
Project Work04
Class record and viva04
Total30

CBSE Syllabus for Class 11 Chemistry Practical

Micro-chemical methods are available for several of the practical experiments. Wherever possible such techniques should be used.

A. Basic Laboratory Techniques
1. Cutting glass tube and glass rod
2. Bending a glass tube
3. Drawing out a glass jet
4. Boring a cork

B. Characterization and Purification of Chemical Substances
1. Determination of melting point of an organic compound.
2. Determination of boiling point of an organic compound.
3. Crystallization of impure sample of any one of the following: Alum, Copper Sulphate, Benzoic Acid.

C. Experiments based on pH

1. Any one of the following experiments:

  • Determination of pH of some solutions obtained from fruit juices, solution of known and varied concentrations of acids, bases and salts using pH paper or universal indicator.
  • Comparing the pH of solutions of strong and weak acids of same concentration.
  • Study the pH change in the titration of a strong base using universal indicator.

2. Study the pH change by common-ion in case of weak acids and weak bases.

D. Chemical Equilibrium
One of the following experiments:

1. Study the shift in equilibrium between ferric ions and thiocyanate ions by increasing/decreasing the concentration of either of the ions.
2. Study the shift in equilibrium between [Co(H2O)6] 2+ and chloride ions by changing the concentration of either of the ions.

E. Quantitative Estimation
i. Using a mechanical balance/electronic balance.
ii. Preparation of standard solution of Oxalic acid.
iii. Determination of strength of a given solution of Sodium hydroxide by titrating it against standard solution of Oxalic acid.
iv. Preparation of standard solution of Sodium carbonate.
v. Determination of strength of a given solution of hydrochloric acid by titrating it against standard Sodium Carbonatesolution.

F. Qualitative Analysis
1) Determination of one anion and one cation in a given salt
Cations‐ Pb2+, Cu2+, As3+, Al3+, Fe3+, Mn2+, Ni2+, Zn2+, Co2+, Ca2+, Sr2+, Ba2+, Mg2+, NH4 +
Anions – (CO3)2‐ , S2‐, NO2‐ , SO32‐, SO2‐ , NO ‐ , Cl‐ , Br‐, I‐, PO43‐ , C2O2‐ ,CH3COO‐
(Note: Insoluble salts excluded)

2) Detection of ‐ Nitrogen, Sulphur, Chlorine in organic compounds.

G) PROJECTS
Scientific investigations involving laboratory testing and collecting information from other sources.

A few suggested projects are as follows:

  • Checking the bacterial contamination in drinking water by testing sulphide ion
  • Study of the methods of purification of water.
  • Testing the hardness, presence of Iron, Fluoride, Chloride, etc., depending upon the regional
    variation in drinking water and study of causes of presence of these ions above permissible
    limit (if any).
  • Investigation of the foaming capacity of different washing soaps and the effect of addition of
    Sodium carbonate on it.
  • Study the acidity of different samples of tea leaves.
  • Determination of the rate of evaporation of different liquids Study the effect of acids and
    bases on the tensile strength of fibres.
  • Study of acidity of fruit and vegetable juices.

Note: Any other investigatory project, which involves about 10 periods of work, can be chosen with the approval of the teacher.

Practical Examination for Visually Impaired Students of Class 11

Below is a list of practicals for the visually impaired students.

A. List of apparatus for identification for assessment in practicals (All experiments)
Beaker, tripod stand, wire gauze, glass rod, funnel, filter paper, Bunsen burner, test tube, test tube stand,
dropper, test tube holder, ignition tube, china dish, tongs, standard flask, pipette, burette, conical flask, clamp
stand, dropper, wash bottle
• Odour detection in qualitative analysis
• Procedure/Setup of the apparatus

B. List of Experiments A. Characterization and Purification of Chemical Substances
1. Crystallization of an impure sample of any one of the following: copper sulphate, benzoic acid
B. Experiments based on pH
1. Determination of pH of some solutions obtained from fruit juices, solutions of known and varied
concentrations of acids, bases and salts using pH paper
2. Comparing the pH of solutions of strong and weak acids of same concentration.

C. Chemical Equilibrium
1. Study the shift in equilibrium between ferric ions and thiocyanate ions by increasing/decreasing
the concentration of eitherions.
2. Study the shift in equilibrium between [Co(H2O)6]2+ and chloride ions by changing the
concentration of either of the ions.

D. Quantitative estimation
1. Preparation of standard solution of oxalic acid.
2. Determination of molarity of a given solution of sodium hydroxide by titrating it against standard
solution of oxalic acid.

E. Qualitative Analysis
1. Determination of one anion and one cation in a given salt
2. Cations – NH+4
Anions – (CO3)2-, S2-, (SO3)2-, Cl-, CH3COO-
(Note: insoluble salts excluded)
3. Detection of Nitrogen in the given organic compound.
4. Detection of Halogen in the given organic compound.

Note: The above practicals may be carried out in an experiential manner rather than recording observations.

We hope students must have found this information on CBSE Syllabus useful for their studying Chemistry. Learn Maths & Science in interactive and fun loving ways with ANAND CLASSES (A School Of Competitions) App/Tablet.

Frequently Asked Questions on CBSE Class 11 Chemistry Syllabus

Q1

How many units are in the CBSE Class 11 Chemistry Syllabus?

There are 9 units in the CBSE Class 11 Chemistry Syllabus. Students can access various study materials for the chapters mentioned in this article for free at ANAND CLASSES (A School Of Competitions).

Q2

What is the total marks for practicals examination as per the CBSE Class 11 Chemistry Syllabus?

The total marks for the practicals as per the CBSE Class 11 Chemistry Syllabus is 30. It includes volumetric analysis, content-based experiment, salt analysis, class record, project work and viva.

Q3

Which chapter carries more weightage as per the CBSE Syllabus for Class 11 Chemistry?

The organic chemistry chapter carries more weightage as per the CBSE Syllabus for Class 11 Chemistry.

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