Halogenation of malonic acid and malonic acid monoethyl ester. Enolisation pathways and enol reactivity

Eberlin, Alex R.; Williams, D. Lyn H.

doi:10.1039/p29960000883

Cited by 9 publications

(6 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…23 Rates for iodination and bromination have been reported to be nearly the same. 24 Extinction coefficients used at 462 nm were 746 M -1 cm -1 for I 2 , and 975 M -1 cm -1 for I 3…”

Section: Methodsmentioning

confidence: 99%

Experimental and Mechanistic Investigation of an Iodomalonic Acid-Based Briggs−Rauscher Oscillator and its Perturbations by Resorcinol

2010

View full text Add to dashboard Cite

Classic Briggs-Rauscher oscillators use malonic acid (MA) as a substrate. The first organic product is iodomalonic acid. Iodomalonic acid (IMA) can serve as a substrate also; thus, the first product in that case is diiodomalonic acid (I(2)MA). Nonoscillating iodination kinetics can be followed by absorbance at 462 nm in acidic KIO(3) so long as IMA is in substantial excess over [I(2)]. At 25 °C, simulations lead to the two most important rate laws, and related rate constant estimates are reported. I(2)MA eventually decomposes by unknown processes, but I(2), O(2), H(2)O(2), and Mn(2+) speed up that decomposition, liberating most of the iodine back to the solution. Resorcinol is an effective inhibitor of oscillations both in MA oscillators and in IMA oscillators. Response of an IMA oscillator to varying amounts of resorcinol is shown herein and is similar to that for MA-based oscillators. The inhibitory effect of resorcinol is diminished by addition of IMA to a MA-based oscillator. The iodination reaction between IMA and resorcinol is too slow (0.043 M(-1) s(-1)) to account for the decreased inhibitory effectiveness of resorcinol. Rather, the decomposition of I(2)MA is responsible for the inhibition decrease.

show abstract

“…23 Rates for iodination and bromination have been reported to be nearly the same. 24 Extinction coefficients used at 462 nm were 746 M -1 cm -1 for I 2 , and 975 M -1 cm -1 for I 3…”

Section: Methodsmentioning

confidence: 99%

Experimental and Mechanistic Investigation of an Iodomalonic Acid-Based Briggs−Rauscher Oscillator and its Perturbations by Resorcinol

2010

View full text Add to dashboard Cite

show abstract

“…Over the years, there have been an extensive number of kinetic studies on the keto‐enol equilibrium mostly on acetophenone or acetyl heterocycle derivatives in water [11–18] with only a few studies on molecules similar to BnFTP [19,20] and an even more limited number in organic solvents [21] . Every kinetic study carried out on the enolization of carbonyls was assessed by either deuteration, racemization, or halogenation, [13] the latter one being the most used [11–18,22−24] . Here we use the racemization approach, conducted with a polarimeter set‐up that continuously samples the racemizing mixture to the polarimeter cell, using a recycle loop connected to the reactor in order to measure directly the enantiomeric excess of the compound during the racemization reaction.…”

Section: Introductionmentioning

confidence: 99%

Fungicide Precursor Racemization Kinetics for Deracemization in Complex Systems

et al. 2020

View full text Add to dashboard Cite

In the racemization area, the keto-enol equilibrium is a major player when it comes to racemizing α-chiral carbonyl compounds. The racemization kinetics in the co-crystal induced deracemization of a fungicide precursor is complex as next to the racemization catalyst, which is a base, an acidic co-former is used to ensure the crystallization of the co-crystal. Here we show that understanding of the racemization kinetics of the target compound is of key importance for optimization of the co-crystallization based deracemization process. The racemization rates in solution as a function of solvent and base concentration were determined by measuring the decreasing enrichment of the chiral ketone due to racemization over time, using a polarimeter setup with a continuous recycling loop through the polarimeter cell. The established racemization kinetics model aligns with the experimental data giving access to the intrinsic racemization rate constant. The proposed mechanism is first order with respect to the enantiomeric excess of the target compound and the base-catalyst concentration. The solvent is shown to strongly affect the racemization constant, with protic solvents increasing this rate substantially due to hydrogen-bond stabilization of the enolate. Finally, we observed the presence of the chiral acid co-former to alter the reaction mechanism albeit remaining first order with respect to the enantiomeric excess. Though more complex, the mechanism still followed Arrhenius law, providing key information on the impact of temperature.

show abstract

Section: Introductionmentioning

confidence: 99%

“…Several mechanisms for the keto‐enol tautomerization of malonic acid have been proposed, including (a) an intramolecular (direct) proton shift, and (b) a water‐mediated proton relay . Initial studies suggested that an intramolecular proton shift was responsible for the tautomerization reaction . A number of later studies, however, showed that the water‐mediated proton relay achieves a significant reduction in the barrier height (activation energy of ~16 kcal/mol), and may thus be the primary tautomerization mechanism for malonic acid in the presence of condensed water.…”

Section: Introductionmentioning

confidence: 99%

Self‐catalyzed keto‐enol tautomerization of malonic acid

Sutton

Lim

Silva

2019

Int J of Quantum Chemistry

View full text Add to dashboard Cite

We demonstrate through quantum chemical calculations that the keto‐enol tautomerization of malonic acid can be catalyzed by the two tautomers of malonic acid itself. This self‐catalyzed process proceeds with a relatively low barrier (Gibbs energy ca. 13 kcal/mol in gas phase, 20 kcal/mol in aqueous phase), and involves the concerted transfer of two protons between the substrate and the carboxylic acid functionality of the malonic acid catalyst. This mechanism is expected to compete with the proton relay mechanism currently favored to explain the tautomerization of malonic acid in aqueous media. Malonic acid is an important constituent of secondary organic aerosol where the present chemistry may play a role in determining chemical composition.

show abstract

Halogenation of malonic acid and malonic acid monoethyl ester. Enolisation pathways and enol reactivity

Cited by 9 publications

References 13 publications

Experimental and Mechanistic Investigation of an Iodomalonic Acid-Based Briggs−Rauscher Oscillator and its Perturbations by Resorcinol

Experimental and Mechanistic Investigation of an Iodomalonic Acid-Based Briggs−Rauscher Oscillator and its Perturbations by Resorcinol

Fungicide Precursor Racemization Kinetics for Deracemization in Complex Systems

Self‐catalyzed keto‐enol tautomerization of malonic acid

Contact Info

Product

Resources

About