Kinetic Studies on the Decarboxylation of Sodium Trifluoroacetate in Ethylene Glycol

Auerbach, I.; Verhoek, Frank H.; Henne, Albert L.

doi:10.1021/ja01157a079

Cited by 33 publications

(21 citation statements)

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“…The same observation has been made by Auerbach [15] during a study on the kinetics of the decomposition of CF3COONa dissolved in glycol-diethylene; he observed a first-order decomposition reaction, with an activation energy of 10 kJmo1-1 at 180 ~ We have extrapolated the Arrhenius plots shown in Fig. The same observation has been made by Auerbach [15] during a study on the kinetics of the decomposition of CF3COONa dissolved in glycol-diethylene; he observed a first-order decomposition reaction, with an activation energy of 10 kJmo1-1 at 180 ~ We have extrapolated the Arrhenius plots shown in Fig.…”

Section: Discussionsupporting

confidence: 81%

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Properties of molten alkali metal trifluoracetates

Dallenbach

Tissot

1981

Journal of Thermal Analysis

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We have studied the thermal stabilities of the alkali metal trifiuoroacetates by means of DTA and TG, and shown that they are stable in the solid form, with the exception of the lithium salt. We have determined the enthalpies of melting of these five salts. We have also studied the kinetics of decomposition of CFaCOONa, of CFaCOOK and of their mixture. This decomposition is in all cases of the first order. The mixture decomposes in two steps, the first one corresponding to the decomposition of the sodium salt.In a previous paper [1 ] we studied the thermal properties of sodium and potassium trifluoroacetates and the binary phase diagram CF3COOK-CF3COONa. This mixture presents a compound and two eutectics ; the stability of the mixture containing 62 wt.% of CF3COOK is sufficient in the molten state to allow its use as an electrolytic medium [2,3]. By means of DTA and TG, we have now investigated the thermal properties of the triftuoroacetates of Li, Na, K, Rb and Cs, and the kinetics of decomposition of the sodium and the potassium salts as well as their mixture. ExperimentalWe have used the same techniques as described previously [1] for preparing the salts and the X-ray analysis. We have analyzed the gases evolved during the decomposition by gas-chromatography (Helwett Packard 5750 B; column: Porapak Q, 10 feet; temperature: 80-170 ~ and by mass-spectrometry (Varian Mat-SM1-BH). DTA and TG measurements have been made with a TA installation (Mettler) under the following conditions: sample and reference (AlzOa) weight: 12-15 mg; crucible: platinum; heating rate: 2 ~ rain-l; atmosphere: N2, 5 lh -1. The enthalpies have been determined with a TA2000 device (Mettler) connected with a micro-computer (Tektronix 4051).

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Section: Discussionsupporting

confidence: 81%

“…According to these results and by analogy with the works of Auerbach [15] and Kirmse [16] dealing with the thermolysis of acetates and trifluoroacetates in solution, one can propose that the step determining this very complicated mechanism is the decarboxylation of the trifluoroacetate ion:…”

Section: Discussionmentioning

confidence: 82%

Properties of molten alkali metal trifluoracetates

Dallenbach

Tissot

1981

Journal of Thermal Analysis

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“…65 A small correction for the solvent effect was taken from the corresponding extrapolation of data for decarboxylation of trichloroacetate in ethylene glycol 65 and the value for water from Table 2. 58 Where possible, we used experimental thermodynamic quantities to calculate equilibrium free energy changes.…”

Section: Resultsmentioning

confidence: 99%

Rate constants for decarboxylation reactions calculated using no barrier theory

et al. 2010

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No barrier theory (NBT) provides both a qualitative way of thinking about what makes a reaction fast or slow and a quantitative way of calculating the rate constant (free energy of activation) corresponding to a particular mechanism. The origin and development of this idea are reviewed and examples of its use for qualitative understanding are presented before applying it to a set of decarboxylations. From the literature, a set of best values for rate constants for decarboxylation was picked. Detailed mechanistic models were developed for reactions leading to delocalized ''anions'' or to localized anions. It was necessary to have pK a values for ionizaion of the carbon acids corresponding to all of these species and these were selected from the literature or estimated by linear free energy relations (or occasionally calculated from proton exchange data). Over the entire range of measured decarboxylation rate constants, a range of 10 25 in rate constant, the calculated values were in good agreement with experiment, with two exceptions: malonate dianion, which has been reported but probably not measured, and glycine, where it is possible that a different mechanism is being followed, unfortunately, one which we do not yet know how to treat by NBT. NBT is both a qualitatively and quantitatively useful tool for understanding chemistry.Résumé : La théorie sans barrière fournit d'une part une façon qualitative de réfléchir sur ce qui fait qu'une réaction est rapide ou lente et d'autre part une façon quantitative de calculer la constante de vitesse (énergie libre d'activation) correspondant à un mécanisme particulier. On passe en revue l'origine et le développement de cette idée et on présente des exemples de son utilisation dans la compréhension qualitative avant de l'appliquer à un ensemble de décarboxylations. On a tiré de la littérature un ensemble des meilleures valeurs pour les constantes de vitesse de décarboxylation. Des modèles de mécanismes réactionnels détaillés ont été développés pour des réactions conduisant à des anions délocalisés ou localisés. Il était nécessaire d'avoir les valeurs de pK a pour l'ionisation des acides carboniques correspondants à chacune des espèces et celles-ci ont été sélectionnées à partir de la littérature ou elles ont été évaluées par des relations d'énergie linéaires ou elles ont été occasionnellement calculées à partir de données d'échange de proton. Sur l'ensemble complet des constantes de vitesse de décarboxylation, une plage de constantes de vitesse relatives s'étalant de 1 à 10 25 , les valeurs calculées ont en bon accord avec les valeurs expérimentales, à deux exceptions près: le dianion de l'acide malonique a été rapporté, mais qui n'a probablement pas été mesuré et la glycine pour laquelle il est possible qu'un mécanisme différent soit impliqué, un mécanisme qu'on ne peut malheureusement pas encore traiter par la théorie sans barrière. La théorie sans barrière (TSB) est un outil qualitativement et quantitativement utile pour la compréhension de la chimie.Mots-clés : décarbox...

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“…[15] The multimethod investigation was required because the disorder in the crystal precluded its formulation as [K(crypt-222)] + CF À 3 on the basis of the X-ray data alone. In our original report, [15] we made it unambiguously clear that the structure could be solved not only for ionic 1, but also for its highly improbable isomer, a 1:1 clathrate of CHF 3 with deprotonated [K(crypt-222)] + , [K(crypt-222{-H + })]ÁCHF 3 (2; Figure 1). There was hardly a need, however, to refine the data for both 1 and 2, as by the time the X-ray diffraction results were obtained, sufficient evidence had already been accrued in favor of 1 and against 2.…”

Section: Introductionmentioning

confidence: 96%

“…The simplest member of the family of perfluorinated carbanions,

{CF}_{3}^{-}

, has long been proposed as an intermediate in a variety of transformations . These include alkaline decarboxylation of trifluoroacetate, deprotonation of fluoroform (CHF 3 ), and Ruppert 's trifluoromethylation of carbonyl compounds ], with his reagent, CF 3 SiMe 3 . There has recently been much discussion in the literature about the possibility of existence of a free

{CF}_{3}^{-}

anion in a condensed phase.…”

Section: Introductionmentioning

confidence: 99%

On the Structure of [K(crypt‐222)]⁺

Harlow¹,

Benet‐Buchholz

Miloserdov

et al. 2018

Helvetica Chimica Acta

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Due to disorder, [K(crypt‐222)]+ CF3− (1) is crystallographically indistinguishable from its isomer, a 1:1 fluoroform clathrate of deprotonated [K(crypt‐222)]+, [K(crypt‐222{‐H+})]·CHF3 (2). In our preceding publications, 1 was characterized on the basis of combined X‐ray diffraction, NMR, reactivity, labeling, acid‐base, and DFT studies. Herein we report that neither incorporation of deuterium nor any other transformation of [K(crypt‐222)]+ is observed in the presence of CD3OD/CD3OK at 70 °C or CD3S(O)CD2K/(D6)DMSO at 23 °C over hours and even days. Since fluoroform is easily and quickly deprotonated under such conditions, the demonstrated greater acidity of CHF3 relative to [K(crypt‐222)]+ provides additional evidence in favor of 1 and against 2. Likewise, crystal packing analysis and DFT calculations support 1, which has now been refined in the ultimately correct space group R32. Our previously drawn conclusions regarding [K(crypt‐222)]+ CF3− and the existence of a ‘naked’ trifluoromethyl anion in a condensed phase remain valid. The recent alternative refinement (Becker and Müller, Chem. Eur. J. 2017, 23, 7081 – 7086) of our raw diffraction data has been improperly performed in the wrong space group to yield a non‐charge‐balanced model [K(crypt‐222)]+·CHF3, which is hereby repudiated. Becker and Müller's attempts to resolve the charge balance issue have produced models that are inadequate from the perspective of both crystallography and chemistry.

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Kinetic Studies on the Decarboxylation of Sodium Trifluoroacetate in Ethylene Glycol

Cited by 33 publications

References 0 publications

Properties of molten alkali metal trifluoracetates

Properties of molten alkali metal trifluoracetates

Rate constants for decarboxylation reactions calculated using no barrier theory

On the Structure of [K(crypt‐222)]⁺

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Kinetic Studies on the Decarboxylation of Sodium Trifluoroacetate in Ethylene Glycol

Cited by 33 publications

References 0 publications

Properties of molten alkali metal trifluoracetates

Properties of molten alkali metal trifluoracetates

Rate constants for decarboxylation reactions calculated using no barrier theory

On the Structure of [K(crypt‐222)]+

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On the Structure of [K(crypt‐222)]⁺