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Here are previous year questions with solutions on Isomerism. Isomerism is commonly seen in organic chemistry and has many applications in chemistry and medicine. Isomers are molecules with the same molecular formula but different arrangements of atoms in space. They may not have similar properties unless they also have the same functional groups in organic chemistry.
Structural isomerism occurs when atoms and functional groups are connected differently. Chain isomerism happens when carbon molecules in the chain of an organic molecule are rearranged, changing the compound’s structure. Organic molecules often have functional groups at the ends, such as halogen or hydroxyl atoms. Moving these groups between two identical compounds creates Positional Isomerism.
Key topics in isomerism include geometrical isomerism, stereoisomerism, chain isomerism, positional isomerism, and functional isomerism. Students can expect one or two questions on this topic. This article helps students understand isomerism questions better. JEE Main questions usually follow a pattern, so reviewing important topics can be helpful. Infinity Learn provides accurate solutions prepared by subject experts. Students can download the questions and solutions in PDF format.
What is Isomerism?
Isomers are particles that have a similar sub-atomic equation however have an alternate game plan of the iotas in space. They don’t really have comparable properties except if they likewise have similar utilitarian gatherings on account of isomerism in natural science.
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Synthetic mixtures that have the same compound formulae however vary in properties and the plan of particles in the atom are called isomers. Subsequently, the mixtures that display isomerism are known as isomers.
“Isomer” is gotten from the Greek words “isos” and “meros”, which actually imply “equivalent parts”. This term was instituted by the Swedish scientific expert Jacob Berzelius in the year 1830.
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Kinds of Isomerism
Primary isomerism is one kind where the molecules and the practical gatherings are combined in various ways. Chain isomerism is seen when the carbon atoms in the chain of a natural particle are migrated, which adjusts the chain of the natural compound. Natural particles as a rule have useful gatherings joined at the terminals like halogen iotas, hydroxyl molecules, and so on The migration of these practical gatherings between two indistinguishable natural mixtures leads to Positional Isomerism.
Also Read: Isomerism – Meaning, Examples and Types
Isomerism Previous Year Questions With Solutions
1. The alkene that exhibits geometrical isomerism is:-
(1) 2–butene
(2) 2–methyl–2–butene
(3) Propene
(4) 2–methylpropene
Solution: (1)
The correct answer is 2-butene.
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2. Which of the following does not show geometrical isomerism?
(1) 1, 2-dichloro -1 – pentene
(2) 1, 3 – dichloro – 2 – pentene
(3) 1, 1 – dichloro – 1 – pentene
(4) 1, 4 – dichloro – 2 – pentene
Solution: (3)
The correct answer is (1, 1 – dichloro – 1 – pentene).
3. Monocarboxylic acids are functional isomers of :
(1) Esters
(2) Amines
(3) Ethers
(4) Alcohols
Solution: (1)
The correct answer is Esters.
4. Identify the compound that exhibits tautomerism:-
(1) 2-Pentanone
(2) Phenol
(3) 2-Butene
(4) Lactic acid
Solution: (1)
The correct answer is 2-Pentanone.
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5. A similarity between optical and geometrical isomerism is that
(1) each forms an equal number of isomers for a given compound
(2) If in a compound one is present then so is the other
(3) both are included in stereoisomerism
(4) they have no similarity
Solution: (3)
The correct answer is both are included in stereoisomerism.
6. Out of the following, the alkene that exhibits optical isomerism is:
(1) 2-methyl-2-pentene
(2) 3-methyl-2-pentene
(3) 4-methyl-1-pentene
(4) 3-methyl-1-pentene
Solution: (4)
The correct answer is 3-methyl-1-pentene.
Two mixtures that contain similar numbers and sorts of iotas, and bonds and different spatial game plans of the particles, yet have non-superimposable perfect representations are called optical isomers. Optical isomers can happen when there is an awry carbon iota. It frames a chiral focus of the particle. 3-methyl-1-pentene shows optical isomerism.
7. Racemic mixture is formed by mixing two
(1) isomeric compounds
(2) chiral compounds
(3) meso compounds
(4) optical isomers
Solution: (4)
The correct answer is optical isomers.
8. Which of the following compounds is not chiral?
(1) 1-chloropentane
(2) 3-chloro-2-methyl pentane
(3) 1-chloro -2-methyl pentane
(4) 2-chloropentane
Solution: (1)
The correct answer is 1-chloropentane.
9. Which of the following will have meso-isomer also?
(1) 2- chlorobutane
(2) 2- hydroxypropanoic acid
(3) 2,3- dichloropentane
(4) 2-3- dichlorobutane
Solution: (4)
The correct answer is 2-3- dichlorobutane.
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10. Which types of isomerism is shown by 2,3-dichlorobutane?
(1) Diastereo
(2) Optical
(3) Geometric
(4) Structural
Solution: (2)
The correct answer is Optical.
11. The alkene that exhibits geometrical isomerism is
(1) propene
(2) 2-methylpropene
(3) 2-butene
(4) 2-methyl -2-butene
Solution: (3)
The correct answer is 2-butene.
12. Of the five isomeric hexanes, the isomer which can give two monochlorinated compounds is
(1) n-hexane
(2) 2, 3-dimethylbutane
(3) 2, 2-dimethylbutane
(4) 2- methyl pentane
Solution: (2)
The correct answer is 2, 2-dimethylbutane.
13. The number of structural isomers for C6H14 is
(1) 3
(2) 4
(3) 5
(4) 6
Solution: (3)
The correct answer is 5.
14. Which one of the following conformations of cyclohexane is chiral?
(1) Boat
(2) Twist boat
(3) Rigid
(4) Chair
Solution: (2)
The correct answer is Twist boat.
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15. The alkene that exhibits geometrical isomerism is
(1) propene
(2) 2-methylpropene
(3) 2-butene
(4) 2-methyl -2-butene
Solution: (3)
The correct answer is 2- butene.
Frequently Asked Questions (FAQs)
What are the two subtypes of stereoisomerism?
Stereoisomerism can be partitioned into the following subtypes-1. Mathematical isomerism - It is otherwise called Cis-Trans isomerism. Those stereoisomers wherein isomerism emerges because of limited revolution of carbon-carbon twofold bond are known as mathematical isomers and this peculiarity is known as mathematical isomerism.
Give an example of a ring chain and position isomerism?
Ring-Chain Isomerism 1 In ring-chain isomerism, one of the isomers has an open-chain structure while different has a ring structure. 2 They for the most part contain an alternate number of pi bonds. 3 An extraordinary illustration of this sort of isomerism can be seen in C 3 H 6. Propene and cyclopropane are the subsequent isomers, as represented underneath. Position Isomerism The places of the utilitarian gatherings or substituent iotas are different in place isomers. Commonly, this isomerism includes the connection of utilitarian gatherings to various carbon iotas in the carbon chain. An illustration of this sort of isomerism can be seen in the mixtures having the recipe C 3 H 7 Cl.
What is Optical Isomerism and how does it differ from Stereoisomerism?
Compounds that display optical isomerism highlight comparable bonds however unique spatial game plans of molecules shape non-superimposable identical representations. These optical isomers are otherwise called enantiomers. Enantiomers vary from one another in their optical exercises. Dextro enantiomers pivot the plane of spellbound light to the right while laevo enantiomers turn it to the left, as delineated underneath. Stereoisomerism: This sort of isomerism emerges in compounds having a similar synthetic equation however various directions of the iotas have a place with the atom in three-layered space. The mixtures that display stereoisomerism are frequently alluded to as stereoisomers. This peculiarity can be additionally ordered into two subtypes. Both these subtypes are momentarily portrayed in this subsection
