Keto-enol tautomerism is observed in (a) C6 H5 COCH3 (b) C6 H5 CHO (c) C6 H5-CO-CH2-CO-CH3

Name: Problem 135, Chapter 23: A Complete Resource Book in Chemistry for JEE Main
Uploaded: 2021-10-09T03:20:54-08:00
Duration: 1 min 1 s
Channel: Narayan Hari
Description: Keto-enol tautomerism is observed in (a) C6 H5 COCH3 (b) C6 H5 CHO (c) C6 H5-CO-CH2-CO-CH3

step 1 So in this problem, ketoinol tautomerism is observed in C6 H5 CO, CHS2COOOH. So according to the

Keto-enol tautomerism is observed in (a) C6 H5 COCH3 (b) C6...

Keto-enol tautomerism is observed in
(a) $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{COCH}_{3}$
(b) $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CHO}$
(c) $\mathrm{C}_{6} \mathrm{H}_{5}-\mathrm{CO}-\mathrm{CH}_{2}-\mathrm{CO}-\mathrm{CH}_{3}$

Key Concepts

Tautomerism

Tautomerism is the phenomenon in which a chemical compound exists in two (or more) readily interconvertible structural forms that differ in the position of a proton and a double bond. These isomers, known as tautomers, typically interconvert through the shifting of atomic nuclei and electrons, often in equilibrium under certain conditions such as heat or acid/base catalysis.

Keto-Enol Tautomerism

Keto-enol tautomerism is a specific type of tautomerism involving the equilibrium between a keto form (containing a carbonyl group) and an enol form (featuring a carbon-carbon double bond adjacent to a hydroxyl group). This interconversion is significant because the enol form can be stabilized by factors such as conjugation and intramolecular hydrogen bonding, which may affect the reactivity and properties of the molecule.

Enol Stabilization Factors

Enol forms are often less abundant than their keto counterparts due to inherent stability differences; however, stabilization factors such as conjugation with adjacent unsaturated systems, resonance effects, and the possibility of forming intramolecular hydrogen bonds can shift the equilibrium in favor of the enol form. These factors lower the energy of the enol form, making its formation more favorable under the right conditions.

Alpha Hydrogen Acidity

For a molecule to undergo keto-enol tautomerism, it must possess acidic alpha hydrogens – hydrogen atoms located on the carbon adjacent to the carbonyl group. The acidity of these hydrogens facilitates their removal, leading to the formation of an enolate intermediate that can reprotonate to form the enol. The ease of deprotonation is a critical factor influencing the position of the tautomeric equilibrium.

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