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Related Concept Videos

Keto–Enol Tautomerism: Mechanism01:14

Keto–Enol Tautomerism: Mechanism

8.0K
The keto and enol forms are known as tautomers and they constantly interconvert (or tautomerize) between the two forms under acid or base catalyzed conditions. Both the reactions involve the same steps—protonation and deprotonation— although in the reverse order.
8.0K
Reactivity of Enols01:18

Reactivity of Enols

4.3K
Enols are a class of compounds where a hydroxyl group is attached to a carbon–carbon double bond, which implies that it is a vinyl alcohol. A carbonyl compound with an α hydrogen undergoes keto–enol tautomerism and remains in equilibrium with its tautomer, the enol form. Usually, the keto tautomer is present in a higher concentration than the enol tautomer due to the higher bond energy of C=O compared to C=C. Moreover, the direction of the keto–enol equilibrium is...
4.3K
Regioselective Formation of Enolates01:33

Regioselective Formation of Enolates

3.6K
As depicted in the figure below, the unsymmetrical ketones can form two possible enolates:  less substituted or more substituted enolates. Usually, the thermodynamic enolates are formed from the more substituted α-carbon atom, while the kinetic enolates are formed faster by deprotonation from the less substituted position. The thermodynamic enolates have lower energy, so they are  more stable. But the energy required to form kinetic enolates is less.
3.6K
Types of Enols and Enolates01:19

Types of Enols and Enolates

3.7K
Aldehydes and ketones form enols, although only about 1% of the enol is present at the equilibrium for simple monocarbonyl compounds. The enol form is undetectable for acetaldehyde, present as only 1.5 × 10−4 % of acetone, and present as only 1.2% of cyclohexanone. Two kinds of regioisomeric enols are possible for unsymmetrical ketones, and their net composition is 1% at equilibrium. This instability is due to the lower bond energy of C=C than the C=O group. The additional...
3.7K
Stereochemical Effects of Enolization01:12

Stereochemical Effects of Enolization

2.7K
The chiral α-carbon of the carbonyl compound is the stereocenter of the molecule. As shown in the figure below, when such a carbonyl compound undergoes racemization under an acidic or basic condition, an achiral enol is formed.
2.7K
Reactivity of Enolate Ions01:23

Reactivity of Enolate Ions

3.4K
Enolate ions are formed by the acid–base reaction of a carbonyl compound with a base. This leads to deprotonation of the α hydrogen atom, leading to a resonance-stabilized enolate ion where one of the contributing structures is an oxyanion, which imparts additional stability. Therefore, the proton on the α carbon is more acidic in nature than that of other sp3-hybridized C–H bonds but less acidic than those in O–H bonds where the negative charge in the conjugate...
3.4K

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Related Experiment Video

Updated: Feb 27, 2026

Highly Stereoselective Synthesis of 1,6-Ketoesters Mediated by Ionic Liquids: A Three-component Reaction Enabling Rapid Access to a New Class of Low Molecular Weight Gelators
06:31

Highly Stereoselective Synthesis of 1,6-Ketoesters Mediated by Ionic Liquids: A Three-component Reaction Enabling Rapid Access to a New Class of Low Molecular Weight Gelators

Published on: November 27, 2015

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Ionic Liquid Gating Enol-Keto Tautomerism.

Adila Adijiang1, Xin Zuo1, Fenglu Hu1

  • 1Institute of Modern Optics, Center of Single-Molecule Sciences, Tianjin Key Laboratory of Micro-Scale Optical Information Science and Technology, Nankai University, Tianjin 300350, China.

Journal of the American Chemical Society
|February 26, 2026
PubMed
Summary
This summary is machine-generated.

Researchers demonstrated reversible keto-enol tautomerism switching in single molecules using electrochemical potential. This breakthrough enables the development of molecular switches with distinct conductance states for advanced electronic applications.

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A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species
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Unraveling Entropic Rate Acceleration Induced by Solvent Dynamics in Membrane Enzymes

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A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species
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Area of Science:

  • Organic Chemistry
  • Molecular Electronics
  • Supramolecular Chemistry

Background:

  • Keto-enol tautomerism is crucial in synthesis, pharmaceuticals, and molecular electronics.
  • Controlling tautomerism at the single-molecule level is essential for developing novel electronic devices.
  • Existing methods for manipulating keto-enol tautomerism are limited, especially at the single-molecule scale.

Purpose of the Study:

  • To develop a reliable method for manipulating keto-enol tautomerism at the single-molecule level.
  • To investigate the mechanism governing keto-enol tautomerism in electrochemical circuits.
  • To demonstrate the potential for creating single-molecule circuit switches.

Main Methods:

  • Utilized a β-diketone derivative as the model compound.
  • Employed electrochemical potential modulation of a gate electrode in an ionic liquid.
  • Analyzed conductance changes associated with keto-enol form switching.

Main Results:

  • Achieved reversible switching between keto and enol forms of the β-diketone derivative.
  • Observed a significant conductance discrepancy between the two tautomeric forms.
  • Provided evidence that proton-coupled electron transfer (PCET) governs the tautomerism in the electrochemical circuit, not intramolecular proton transfer (IPT).

Conclusions:

  • Successfully demonstrated single-molecule control over keto-enol tautomerism via electrochemical gating.
  • The findings clarify the mechanism of tautomerism in electrochemical circuits, identifying PCET as the key process.
  • This work paves the way for fabricating single-molecule circuit switches and advancing applications of tautomerism.