Which among the given molecules can exhibit tautomerism?
- III only
- Both I and III
- Both I and II
- Both II and III
The Correct Option is A
Solution and Explanation
Tautomerism refers to a phenomenon where isomers (called tautomers) rapidly interconvert through the migration of a proton (H⁺) or a hydrogen atom within a molecule. This usually happens between two structural forms that differ only in the position of a hydrogen atom and a double bond.
α-Hydrogen: In organic chemistry, α-hydrogen refers to the hydrogen atoms attached to the carbon adjacent to a functional group (often a carbonyl group). These hydrogens are typically involved in reactions like tautomerism.
Bridge Carbon: A bridge carbon is part of a cyclic structure in some molecules where it connects two parts of a ring.
α-Hydrogen at a bridge carbon does not participate in tautomerism because it is less likely to form a structure where the hydrogen can migrate in the tautomeric transition.
Only (III) exhibits tautomerism, indicating that in this specific case, the other molecules (presumably labeled (I) and (II)) do not undergo tautomerism due to the lack of α-hydrogens or because they are involved in a more rigid structure.
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Concepts Used:
Organic Chemistry – Some Basic Principles and Techniques - Reaction Mechanism
SN1 Reaction Mechanism:
SN1 reaction mechanism takes place by following three steps –
- Formation of carbocation
- Attack of nucleophile
- Deprotonation
SN2 Reaction Mechanism:
The SN2 reaction mechanism involves the nucleophilic substitution reaction of the leaving group (which generally consists of halide groups or other electron-withdrawing groups) with a nucleophile in a given organic compound.
Electrophilic Aromatic Substitution Reaction Mechanism:
The mechanism of an electrophilic aromatic substitution reaction contains three main components which are:
- A new sigma bond from C=C is formed during the reaction in the arene nucleophile.
- Due to the breaking of the C-H sigma bond, a proton is removed.
- The C=C bond is reformed and it restores the aromaticity of the compound.
Electrophilic Substitution Reaction Mechanism:
The electrophilic substitution reaction mechanism is composed of three steps, which will be discussed more below.
- Electrophile Generation
- Carbocation Formation
- Proton Removal