The dihedral angle of the least stable conformer of ethane is
The dihedral angle of the least stable conformer of ethane is
0°
120°
180°
60°
The Correct Option is D
Solution and Explanation
The question is about the dihedral angle of the least stable conformer of ethane. To understand this, we need to explore the concept of conformers and their stability in ethane.
For ethane (C2H6), the molecule can rotate around the carbon-carbon sigma (σ) bond, resulting in different spatial arrangements of the hydrogen atoms attached to these two carbon atoms. These different arrangements are known as conformations or conformers.
Two common conformers of ethane are:
- Staggered Conformer: In the staggered conformation, the hydrogen atoms on one carbon atom are positioned such that they are as far apart as possible from the hydrogens on the adjacent carbon. This arrangement minimizes the torsional strain, making it the most stable form. The dihedral angle in this conformation is \(60^\circ\).
- Eclipsed Conformer: In the eclipsed conformation, the hydrogen atoms on one carbon are directly aligned with the hydrogens on the adjacent carbon. This results in maximum torsional strain due to electron repulsion, making it the least stable form. The dihedral angle in this conformation is \(0^\circ\).
Now, when the question asks for the dihedral angle of the least stable conformer of ethane, it refers to the eclipsed conformer, where the dihedral angle is \(0^\circ\). However, due to likely mismatches in the options, let's analyze them:
- 0°: This corresponds to the eclipsed form, the least stable conformer typically.
- 60°: Represents the staggered form, which is actually the most stable.
- 120°: This dihedral angle can also depict a staggered conformation in certain representations, again more stable than eclipsed.
- 180°: Represents an anticonformation in linear molecules, not relevant here for stability context.
Since it appears there might be a misunderstanding with the correct answer provided, typically, the eclipsed conformer with a dihedral angle of \(0^\circ\) is the least stable due to its torsional strain. Make sure to cross-check the provided options since \(60^\circ\) does refer to the most stable staggered conformation, not the least stable one.
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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.