Nomenclature of Alkanes, Alkenes and Alkynes – IUPAC Nomenclature of Alkanes, Alkenes and Alkynes

February 14, 2025December 16, 2024 by Neeraj Anand, Param Anand

What is IUPAC Nomenclature?

A single chemical compound can have several acceptable systematic names and the systematic method of naming organic chemical compounds is called IUPAC Nomenclature but no two compounds can have the same name.

IUPAC Nomenclature

Earlier, most of the compounds with the same structural formula were known by different names depending on the regions where they were synthesized. This naming system was very trivial since it raised a lot of confusion. Finally, a common naming system enlisting the standard rules was set up by IUPAC (International Union for Pure and Applied Chemistry) for the naming of compounds. This method of naming is known as IUPAC naming or IUPAC nomenclature.

Nomenclature the way that names are given to things is one main point of difference between the language of chemistry as of other science and natural languages. The other is the importance of the written language compared with the spoken one. In chemistry there are several nomenclatures not only elements and compounds must be named but also reactions methods, pieces of apparatus and theoretical concepts.

IUPAC Nomenclature of Alkanes, Alkynes, and Alkenes

This method of naming is known as IUPAC naming or IUPAC nomenclature. IUPAC nomenclature of alkanes, alkynes, and alkenes are explained below:

Alkanes are the simplest hydrocarbons known to us. They have a general formula of C_nH_2n+2. Alkanes belong to the family of saturated hydrocarbons that is; they contain only sigma bond linkages between carbon and hydrogen. The organic compounds form a series, known as homologues series in which the successive compounds contain the same functional group and differ from one another by a ‘–CH₂’ group.

Alkenes and alkynes, on the other hand, are unsaturated hydrocarbons. In the case of alkenes, double bond linkages are seen and in alkynes, triple bond linkages are present. Rules underlying IUPAC nomenclature of alkanes, alkenes, and alkynes are discussed below:

The longest hydrocarbon chain is selected and is termed as parent chain in case of alkanes. In the case of alkenes and alkynes, hydrocarbon chain with the double and triple bond is chosen as parent chain. The parent chain is named with the help of Greek alphabets such as hepta, octa etc.
For alkanes suffix ‘-ane’ is used, for alkenes, the suffix ‘-ene’ is used and the suffix ‘yne’ is used for alkynes. For example, C₂H₆ is known as ethane, C₂H₄ is known as ethene and C₂H₂ is known as ethyne.
The parent chain is numbered such that we reach to the double-bonded or triple bonded carbon atom earliest. The position of the carbon atom with the double bond is mentioned in numerals. For example, CH₃CH=CHCH₂CH₃ is named as Pent-2-ene.
In the case of multiple double bonds in the carbon chain, Greek numerical prefixes such as di, tri are used to denote their number.

Unsaturated Carbon Chains – Alkene Formula

Hydrocarbons in which one or more of the carbon atoms in the chain are bonded to another by a double or a triple bond are said to be unsaturated. The two families of unsaturated hydrocarbons are alkenes and alkynes.

Alkenes of hydrocarbons has one double bond between carbon atoms. Like the alkenes, their molecular formula increases by a fixed amount with each carbon atom added to the chain. A family of compounds that grows in such a way is called a homologous series. Alkenes bear the general formula CnH2n. Note that this is the same as the alkane formula, except that we subtract two hydrogen atoms to allow for the double bond.

IUPAC System of Alkenes

The longest carbon chain containing the carbon-carbon double bond is selected as the parent alkene.
The suffix ‘ane’ of the alkane is replaced by ‘ene’. If a double bond occurs twice or thrice in the parent chain the alkene is called diene or triene respectively.
The position of double bonds or side chains indicated by numbers 1, 2, 3 etc.
The longest chain is numbered from that end, which gives the lowest number to the carbon atom of the double bond and written just before the suffix ‘ene’. If while numbering the chain the double bond gets the same number from either side the carbon chain is numbered in such a manner that the substituent gets the lowest number.
In case there are two or more double bonds, the lowest sum rule should be followed.
The name and position of other groups (substituents) is indicated by prefixes.

Alkene Formula

Named alkenes are unsaturated molecules. This means they contain at least one double bond of carbon-carbon which displaces two atoms of hydrogen and, thus, alkenes do not have the maximum number of atoms of hydrogen per atom.

For the homologous series of alkenes, the general formula is CnH2n where n is the number of carbon atoms. Because alkenes are hydrocarbons, the alkene homologous series starts at ethene C2H4, with at least one carbon-carbon double bond.

The compounds are called alkanes, but with the end, “ene” rather than “ane.” Each successive molecule in the homologous series of alkenes is formed by adding to the preceding molecule one carbon and two hydrogen atoms or one CH2 (methylene group). Accordingly, the incremental change in relative molecular mass is 14.

Frequently Asked Questions – FAQs

What is meant by IUPAC nomenclature?

IUPAC is an acronym for the International Union of Pure and Applied Chemistry, an internationally recognized body that has systematically named all chemical organic substances.

How do you identify an alkene?

A simple bromine water test might be used to tell the difference between an alkane and an alkene. As the bromine reacts with the carbon-carbon double bond, an alkene can turn brown bromine water colourless. This reaction will actually occur for unsaturated compounds containing double bonds in carbon-carbon form.

How do we name alkenes?

Alkenes and alkynes are named for the longest chain containing the double or triple bond. The chain is numbered to minimize the number of double or triple bonds assigned to it. The compound suffix is “-ene” for an alkene, or “-yne” for an alkyne.

What are the basic rules to be followed while naming the carbon compound?

The compound name is written in alphabetical order with the substituents followed by the base name (derived from the number of carbons in the parent chain). Commas are used for numbers, and dashes for letters and numbers are used. The Name has no spaces.

What is the prefix in IUPAC name?

The prefix oct- tells us that in the longest chain there are eight carbon atoms. … The prefix hex- tells us that in the longest row, there are six carbon atoms. The -ane suffix tells us that this is an alkane and that only single carbon-carbon bonds and no other functional groups occur.

What is the structure of aldehyde?

Aldehyde is a class of organic compounds in which a carbon atom has a double bond with an atom of oxygen, a single bond with an atom of hydrogen, and a single bond with another atom or group of atoms.

Is aldehyde a functional group?

Organic compounds that incorporate a carbonyl functional group, C = O, are aldehydes and ketones. There are two remaining bonds in the carbon atom of this group that can be occupied by hydrogen or alkyl or aryl substituents. The compound is an aldehyde if at least one of these substituents is hydrogen.

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.

...

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 Scheme	Marks
Volumetric Analysis	08
Salt Analysis	08
Content Based Experiment	06
Project Work	04
Class record and viva	04
Total	30

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‐ , S^2‐, NO₂^‐ , SO₃^2‐, SO^2‐ , NO ^‐ , Cl^‐ , Br^‐, I‐, PO₄^3‐ , 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

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).

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.

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.