Which of the following biphenyls is optically active ?
The Correct Option is A
Solution and Explanation
In some molecules, chirality is a key property that determines whether a molecule is optically active. A molecule is optically active if it can rotate plane-polarized light, and this typically occurs when the molecule lacks any symmetry elements like a plane of symmetry or center of symmetry.
Phenyl rings: If two phenyl rings are placed in different planes (i.e., they are not coplanar), this can lead to a situation where the molecule has asymmetry, meaning it lacks a plane of symmetry.
Absence of plane of symmetry: A molecule without a plane of symmetry typically means that it cannot be superimposed onto its mirror image, which is a characteristic of chiral molecules.
Optically active: Since the molecule is chiral (due to the lack of symmetry and the presence of different planes for the phenyl rings), it is optically active. This means it can rotate the plane of polarized light.
In conclusion, if both phenyl rings are in different planes, there is no plane of symmetry, and the molecule is optically active due to its chirality.
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Concepts Used:
Haloalkanes and Haloarenes
The hydrocarbons such as Haloalkanes and Haloarenes are the ones, in which one or more hydrogen atoms are replaced with halogen atoms. The main difference between Haloalkanes and Haloarenes is that Haloalkanes are derived from open chained hydrocarbons, also called alkanes, and Haloarenes are derived from aromatic hydrocarbons.
- Haloalkanes have hydrocarbons made up of aliphatic alkanes and one or more hydrogen atoms replaced by halogens (elements such as Chlorine, Bromine, Fluorine, Iodine, etc.) whereas, haloarenes consist of aromatic ring or rings and one or more hydrogen atoms replaced by halogens.
- In haloalkanes, the halogen atom is attached to the sp3 hybridized carbon atom of the alkyl group whereas, in haloarenes, the halogen atom is attached to the sp3 hybridized carbon atom of the alkyl group.
- Haloalkanes are saturated organic compounds where all the chemical bonds are attached to the carbon atom with single bonds and a single carbon atom is attached to the Halogen atom, whereas, the haloarenes differ from Haloalkanes by their method of preparation and properties.
- Haloalkanes are made by aliphatic alkanes by the process of free radical halogenation, whereas, haloarenes are made by direct halogenation of aromatic rings.
- Haloalkanes are odorless compounds, whereas, haloarenes have a sweet odor.
- Haloalkanes precipitate in SN2 substitution reactions, whereas, haloarenes do not precipitate in SN2 substitution reactions.
- Example of haloalkanes is CH3Cl (Methyl Chloride) and CH3CH2Br (Ethyl Bromide) and the example of haloarenes is Chlorobenzene, Bromobenzene.