Correction to Substituent Effects on Keto–Enol Equilibria Using NMR Spectroscopy

Manbeck, Kimberly A.; Boaz, Nicholas C.; Bair, Nathaniel C.; Sanders, Allix; Marsh, Anderson L.

doi:10.1021/ed200768s

Cited by 3 publications

(1 citation statement)

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“…Since the concept of keto–enol tautomerism equilibrium is such a fundamental phenomenon in many areas of chemistry, a range of applications has been introduced as laboratory experiments in both physical and physical–organic chemistry laboratories. Among them, many notable publications utilize nuclear magnetic resonance (NMR) as a means to follow the equilibrium process. − Advanced experimental procedures have been developed to address kinetic and thermodynamic concepts , of keto–enol tautomerism. In particular, Cook and Feltman introduced the importance of solvent effects, , and more recently Sandusky expanded the approach in the context of the Onsager–Kirkwood theory, thus directly relating to the classic Meyer’s Rule established more than a century ago.…”

Section: Introductionmentioning

confidence: 99%

Keto–Enol Tautomerization of Acetylacetone in Mixed Solvents by NMR Spectroscopy. A Physical Chemistry Experiment on the Application of the Onsager-Kirkwood Model for Solvation Thermodynamics

Cortney

Krishnan

2020

J. Chem. Educ.

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Keto–enol tautomerism is a fundamental concept that examines the migration of a proton between two constitutional isomers, the keto and enol tautomer. Many experiments have been proposed to understand the concept behind Meyer’s Rule, which states that the keto tautomer is favored as the solvent polarity increases. However, all the experiments have only been performed in a single solvent. A new physical chemistry experiment is introduced to determine tautomerization equilibrium in binary solvent mixtures using nuclear magnetic resonance (NMR) spectroscopy, by systematically varying the molar ratio of the solvents. This approach allows the students to explore the variation of the polarity of the solvent system as a continuous variable. Furthermore, using an empirical method, the solvent polarity at any binary solvent condition can be converted to an effective dielectric constant of the sample. Because of this ability, the keto–enol tautomerization equilibrium constant can be directly related to the solvation Gibbs energy using the Onsager–Kirkwood theory. Detailed experimental procedures for the direct adaptation of the experiment using a high-resolution or desktop NMR spectrometer is provided in the Supporting Information.

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Section: Introductionmentioning

confidence: 99%

Keto–Enol Tautomerization of Acetylacetone in Mixed Solvents by NMR Spectroscopy. A Physical Chemistry Experiment on the Application of the Onsager-Kirkwood Model for Solvation Thermodynamics

Cortney

Krishnan

2020

J. Chem. Educ.

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Measuring Structural and Electronic Effects on Keto–Enol Equilibrium in 1,3-Dicarbonyl Compounds

et al. 2016

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Nuclear magnetic resonance (NMR) spectroscopy is an integral part of the undergraduate chemistry curriculum. In addition to structure determination, NMR spectroscopy is used to analyze chemical reactions and equilibria in situ. Determination of the position of equilibria is well-suited to NMR analysis in the undergraduate laboratory as an extension of peak identification and signal integration, and the determination of keto−enol equilibrium remains a popular undergraduate laboratory experiment. Several factors affect the position of keto−enol equilibrium, defined here as K e/k = [enol]/[keto], including structure (steric bulk, conjugation, electron-withdrawing/donating groups, resonance), temperature, and solvent. A judiciously selected set of compounds that have a common 1,3-dicarbonyl moiety with progressively changing ligands at the 1 and 3 positions is presented. This array allows students to investigate structure−function relationships that affect keto−enol equilibrium in a cumulative fashion and affords instructors a broad selection of compounds for study in both introductory and advanced laboratory courses using a variety of pedagogic approaches.

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Utilizing NMR To Study Structure and Equilibrium in the Organic Chemistry Laboratory

Young

Smith

DeBlasio

et al. 2016

ACS Symposium Series

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Correction to Substituent Effects on Keto–Enol Equilibria Using NMR Spectroscopy

Cited by 3 publications

References 0 publications

Keto–Enol Tautomerization of Acetylacetone in Mixed Solvents by NMR Spectroscopy. A Physical Chemistry Experiment on the Application of the Onsager-Kirkwood Model for Solvation Thermodynamics

Keto–Enol Tautomerization of Acetylacetone in Mixed Solvents by NMR Spectroscopy. A Physical Chemistry Experiment on the Application of the Onsager-Kirkwood Model for Solvation Thermodynamics

Measuring Structural and Electronic Effects on Keto–Enol Equilibrium in 1,3-Dicarbonyl Compounds

Utilizing NMR To Study Structure and Equilibrium in the Organic Chemistry Laboratory

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