Reversibility of the catalytic ketonization of carboxylic acids and of beta-keto acids decarboxylation

Ignatchenko, Alexey V.; Cohen, Andrew J.

doi:10.1016/j.catcom.2018.04.002

Cited by 15 publications

(23 citation statements)

References 18 publications

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“…4,19 Therefore, the most likely reason for the above inhibition is the reketonization reaction according to Scheme 12, which is more prevalent compared to the recently reported condensation between acetone and carbon dioxide. 12…”

Section: Discussionmentioning

confidence: 99%

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Equilibrium in the Catalytic Condensation of Carboxylic Acids with Methyl Ketones to 1,3-Diketones and the Origin of the Reketonization Effect

et al. 2019

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Acetone is the expected ketone product of an acetic acid decarboxylative ketonization reaction with metal oxide catalysts used in the industrial production of ketones and for biofuel upgrade. Decarboxylative cross-ketonization of a mixture of acetic and isobutyric acids yields highly valued unsymmetrical methyl isopropyl ketone (MIPK) along with two less valuable symmetrical ketones, acetone and diisopropyl ketone (DIPK). We describe a side reaction of isobutyric acid with acetone yielding the cross-ketone MIPK with monoclinic zirconia and anatase titania catalysts in the absence of acetic acid. We call it a reketonization reaction because acetone is deconstructed and used for the construction of MIPK. Isotopic labeling of the isobutyric acid’s carboxyl group shows that it is the exclusive supplier of the carbonyl group of MIPK, while acetone provides only methyl group for MIPK construction. More branched ketones, MIPK or DIPK, are less reactive in their reketonization with carboxylic acids. The proposed mechanism of reketonization supported by density functional theory (DFT) computations starts with acetone enolization and proceeds via its condensation with surface isobutyrate to a β-diketone similar to β-keto acid formation in the decarboxylative ketonization of acids. Decomposition of unsymmetrical β-diketones with water (or methanol) by the retrocondensation reaction under the same conditions over metal oxides yields two pairs of ketones and acids (or esters in the case of methanol) and proceeds much faster compared to their formation. The major direction yields thermodynamically more stable products—more substituted ketones. DFT calculations predict even a larger fraction of the thermodynamically preferred pair of products. The difference is explained by some degree of a kinetic control in the opposite direction. Reketonization has lower reaction rates compared to regular ketonization. Still, a high extent of reketonization occurs unnoticeably during the decarboxylative ketonization of acetic acid as the result of the acetone reaction with acetic acid. This degenerate reaction is the major cause of the inhibition by acetone of its own rate of formation from acetic acid at high conversions.

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Section: Discussionmentioning

confidence: 99%

“…That is to say, ketones can enolize and condense with carbon dioxide back to β-keto acids—unstable intermediates. 12…”

Section: Introductionmentioning

confidence: 99%

Equilibrium in the Catalytic Condensation of Carboxylic Acids with Methyl Ketones to 1,3-Diketones and the Origin of the Reketonization Effect

et al. 2019

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“…Accordingly, it was assumed that enolisation is the rate-limiting step of the ketonization reaction. At the moment, the beta-keto-acid-intermediate-based mechanism is considered the most plausible [19,[30][31][32][33][34]37,39]. The last two mechanisms require a stage of enolization with the elimination of hydrogen in the alpha position to the carboxyl group [19,[30][31][32][33][34].…”

Section: Scheme 1 Simplified Schemes Of Possible Ketonization Mechanmentioning

confidence: 99%

“…Rather the loss of the CO 2 or the formation of a new C-C bond are the likely rate-determining steps [26,32,33,36]. Despite the enormous efforts spent on the establishment of the mechanism of this reaction, kinetic studies, isotope effect studies [26,27,36], quantum chemical calculations [30][31][32][33]36], studies of cross-ketonization reactions [28,30,33,38], 13 C/ 12 C exchange studies [34], H/D exchange studies on the catalyst surfaces [28,29,39], experiments with 13 C-labeled acetic acids [28,33,34], Fourier Transform Infrared Spectroscopy FT-IR studies [36,37,[39][40][41], etc., the question of establishing the full details of the ketonization reaction mechanism is still not completely closed [39]. However, linear free energy relationships (LFERs) have never been applied to study of the mechanism of ketonization.…”

Section: Kinetic Studymentioning

confidence: 99%

“…Despite the close attention to the ketonization reaction, last year's publications [15][16][17][18], including numerous studies and reviews [16,17,[19][20][21][22][23] suggested that the mechanism of this reaction is not completely clear. Over the past few decades, several basic mechanisms of this reaction have been proposed : (i) free-radical mechanism [24], (ii) direct concerted mechanism [20,25], (iii) mechanism involving an acyl intermediate [26], (iv) ketene based mechanisms [27][28][29], (v) and a betaketo-acid-intermediate based mechanisms [30][31][32][33][34][35] (Scheme 1). The free-radical mechanism, the acylbased mechanism, and ketene-based mechanism involve the participation of free radicals, acylium cation and ketene species as key intermediates of ketonization, respectively.…”

Section: Introductionmentioning

confidence: 99%

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Catalytic Pyrolysis of Aliphatic Carboxylic Acids into Symmetric Ketones over Ceria-Based Catalysts: Kinetics, Isotope Effect and Mechanism

2020

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Ketonization is a promising way for upgrading bio-derived carboxylic acids from pyrolysis bio-oils, waste oils, and fats to produce high value-added chemicals and biofuels. Therefore, an understanding of its mechanism can help to carry out the catalytic pyrolysis of biomass more efficiently. Here we show that temperature-programmed desorption mass spectrometry (TPD-MS) together with linear free energy relationships (LFERs) can be used to identify catalytic pyrolysis mechanisms. We report the kinetics of the catalytic pyrolysis of deuterated acetic acid and a reaction series of linear and branched fatty acids into symmetric ketones on the surfaces of ceria-based oxides. A structure–reactivity correlation between Taft’s steric substituent constants Es* and activation energies of ketonization indicates that this reaction is the sterically controlled reaction. Surface D3-n-acetates transform into deuterated acetone isotopomers with different yield, rate, E≠, and deuterium kinetic isotope effect (DKIE). The obtained values of inverse DKIE together with the structure–reactivity correlation support a concerted mechanism over ceria-based catalysts. These results demonstrate that analysis of Taft’s correlations and using simple equation for estimation of DKIE from TPD-MS data are promising approaches for the study of catalytic pyrolysis mechanisms on a semi-quantitative level.

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Decarboxylative Ketonization of Aliphatic Carboxylic Acids in a Continuous Flow Reactor Catalysed by Manganese Oxide on Silica

Goebel,

Belitz,

Prendes

et al. 2024

ChemSusChem

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The sustainable synthesis of long carbon chain molecules from carbon dioxide, water and electricity relies on the development of waste‐free, highly selective C–C bond forming reactions. An example for such a power‐to‐chemicals process is the industrial‐scale fermentation for the production of hexanoic acid. Herein, we describe how this product is transformed into 6‐undecanone via decarboxylative ketonization using a heterogeneous manganese oxide / silica catalyst. The reaction reaches full conversion with near‐complete selectivity when carried out in a continuous flow reactor, requires no solvent or carrier gas, and releases carbon dioxide and water as the only by‐products. The reactor was operated for several weeks with no loss of reactivity, producing 7 kg of 6‐undecanone from 10 g of catalyst and achieving a productivity of 1.135 kg per litre of reactor volume per hour. 6‐Undecanone and other long‐chain ketones accessible this way can be hydrogenated to industrially meaningful alkanes, or converted into valuable fatty acids via a hydrogenation / elimination / isomerizing hydrocarboxylation sequence.

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Reversibility of the catalytic ketonization of carboxylic acids and of beta-keto acids decarboxylation

Abstract: Reversibility of the catalytic ketonization of carboxylic acids and of beta-keto Reversibility of the catalytic ketonization of carboxylic acids and of beta-keto acids decarboxylation acids decarboxylation

Cited by 15 publications

References 18 publications

Equilibrium in the Catalytic Condensation of Carboxylic Acids with Methyl Ketones to 1,3-Diketones and the Origin of the Reketonization Effect

Equilibrium in the Catalytic Condensation of Carboxylic Acids with Methyl Ketones to 1,3-Diketones and the Origin of the Reketonization Effect

Catalytic Pyrolysis of Aliphatic Carboxylic Acids into Symmetric Ketones over Ceria-Based Catalysts: Kinetics, Isotope Effect and Mechanism

Decarboxylative Ketonization of Aliphatic Carboxylic Acids in a Continuous Flow Reactor Catalysed by Manganese Oxide on Silica

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