Which of the following is chiral?
- $Cl - CH _{2}- CH _{2}- CH _{2}- CH _{2}- CH _{3}$
- $CH _{3}- CH _{2}- \underset{\overset{|}{Cl}}{C}H - CH _{2}- CH _{3}$
- $Cl - CH = CH - CH _{2}- CH _{2}- CH _{3}$
- $H -\underset{\overset{|}{Cl}}{C}=C= CH- CH_2-CH _{3}$
The Correct Option is D
Solution and Explanation
[a] $ClCH _{2} CH _{2} CH _{2} CH _{2} CH _{3}$ achiral molecule, absence of asymmetrical carbon atom.
[b] $CH _{3}- CH _{2}- \underset{\overset{|}{Cl}}{C}H - CH - CH _{3}$ achiral molecule, absence of assymmetrical carbon atom.
[c] $Cl - CH = \underset{\text{achiral molecule}}{CH- CH _{2}}-CH_2- CH _{3}$
[d] Allenes exhibits optical isomerism Central), provided that the two groups attached to each terminal carbon atoms are different.
Top Questions on Isomerism
- Match List - I with List - II.
List - I (Pair of Compounds) List - II (Isomerism) (A) n-propanol and Isopropanol (I) Metamerism (B) Methoxypropane and ethoxyethane (IV) Functional Isomerism (C) Propanone and propanal (III) Position Isomerism (D) Neopentane and Isopentane (II) Chain Isomerism - The number of optical isomers in following compound is : _____.
- Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): The total number of geometrical isomers shown by [Co(en)$_2$Cl$_2$]$^+$ complex ion is three.
Reason (R): [Co(en)$_2$Cl$_2$]$^+$ complex ion has an octahedral geometry.
In the light of the above statements, choose the most appropriate answer from the options given below: - Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): Cis form of alkene is found to be more polar than the trans form
Reason (R): Dipole moment of trans isomer of 2-butene is zero. In the light of the above statements.
Choose the correct answer from the options given below :
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Concepts Used:
Isomerism
Isomerism
In simple words, multiple compounds having the same molecular formulae but different structural formulae are referred to as isomers and this entire phenomenon is described as ‘Isomerism’. ‘Isos’ and ‘meros’ are Greek words that translate to ‘equal parts’.
Types of Isomerism:
Isomerism can be differentiated by primary types and their subtypes.
- Structural Isomerism
Ring Chain Isomerism, Chain Isomerism, Tautomerism, Functional Isomerism, Metamerism, and Positional Isomerism are the subtypes of Structural Isomerism.
- Stereoisomerism
Optical Isomerism & Geometric Isomerism are the two subtypes of Stereoisomerism.
Read More: Isomerism in Coordination Compounds
Structural Isomerism
The phenomenon when the compounds start showing isomerism because of their different structure is termed Structural Isomerism. Example - Isobutane and n-butane
Structural Isomerism can further be classified into various types such as chain isomerism, positional isomerism, functional isomerism, metamerism, ring-chain isomerism, and tautomerism.
- Ring Chain isomerism
In the ring chain isomerism, there will be an open-chain structure in any one of the isomers and the remaining will have a closed chain or a ring structure. These kinds of compounds are known as ring chain isomers and this phenomenon is termed ring chain isomerism. The number of pi bonds in ring chain isomers will be different. Example - Cyclopropane and Propene. Their molecular formula is C3H6
- Chain isomerism
In chain isomerism, there will be different branches of carbon atoms in multiple isomers compounds but still, their molecular formula remains the same. Skeleton isomerism is the other term used to refer to chain isomerism. Example- 2 methyl butane, 2-2 dimethyl propane, and n-pentane. Their molecular formula is C5H12
- Tautomerism
In tautomerism, there will be a difference in isomer compounds only in the position of electrons, protons, and atoms. Tautomers take place in an equilibrium state as they can easily interchange. Example - Keto-enol tautomerism
- Functional Isomerism
In functional isomerism, the isomer compounds with different functional groups have the same molecular formula. Example - dimethyl ether and ethanol. They both have the same molecular formula C2H6 O. The functional group of Ethanol is ‘OH’ while the Functional group of dimethyl ether is ‘R-O-R’.
- Metamerism
In metamerism, each side of the functional group has the presence of different alkyl chains. Compared with other types of isomerism, metamerism is rarely found and is constrained to molecules with atoms. Example - Methoxy-propane (CH3OC3H7) & ethoxyethane (C2H5OC2H5)
- Positional Isomerism
In Positional isomerism, the functional groups and substituents of a structural isomer will have different positions. Example - 1-Chloropropane and 2-Chloropropane
Stereoisomerism
The phenomenon when compounds start showing different spatial arrangements of atoms even when their molecular formula is the same is termed Stereoisomerism. Example - 1,2 - dichloroethene (C2H2CI2)
- Optical isomerism
In optical isomerism, the isomer Compounds differ in terms of optical activity but are mirror images of each other. In this subtype of Stereoisomerism, carbon atoms are connected to four different groups and this is known as the chiral center. Enantiomers is the term mostly used to refer to optical isomers.
In Dextro optical isomers plane of polarized light is rotated to the right. In Laevo optical Isomers, the plane of polarized light is rotated to the left.
- Geometric isomerism
In geometric isomerism, the spatial positions of molecules are locked because of the presence of a double bond or ring structure. It is often referred to as Cis-Trans isomerism. Groups connected to ring structure carbon atom must be different in geometric isomerism.
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