The acidity and tautomerism of β-diketones in aqueous solution

Bunting, John W.; Kanter, James P.; Nelander, Raymond; Wu, Zhennan

doi:10.1139/v95-161

Cited by 50 publications

(51 citation statements)

References 13 publications

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“…[16][17][18] and references therein). [19][20][21][27][28][29][30][31][32][33][34][35][36][37][38][39] The situation is different for the interconversion mechanism. Tautomerism in b-diketone compounds is a particular case since the enolone (also called keto-enol) form of most b-diketones is more stable than the diketo form owing to strong intramolecular hydrogen bonds.…”

Section: Introductionmentioning

confidence: 99%

Probing keto–enol tautomerism using photoelectron spectroscopy

Capron

Casier

Sisourat

et al. 2015

Phys. Chem. Chem. Phys.

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We theoretically investigate the mechanism of tautomerism in the gas-phase acetylacetone molecule. The minimum energy path between the enolone and diketo forms has been computed using the Nudged-Elastic Band (NEB) method within the density-functional theory (DFT) using the projector augmented-wave method and generalized gradient approximation in Perdew-Wang (PW91) parametrization. The lowest transition state as well as several intermediate geometries between the two stable tautomers have been identified. The outer-valence ionization spectra for all determined geometries have been computed using the third-order non-Dyson algebraic diagrammatic construction technique. Furthermore, the oxygen core-shell ionization spectra for these geometries have been obtained using DFT and the Becke three-parameter Lee-Yang-Parr (B3LYP) functional. It is shown that all spectra depend strongly on the geometries demonstrating the possibility of following the proton-transfer dynamics using photoelectron spectroscopy in pump-probe experiments.

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Section: Introductionmentioning

confidence: 99%

Probing keto–enol tautomerism using photoelectron spectroscopy

Capron

Casier

Sisourat

et al. 2015

Phys. Chem. Chem. Phys.

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“…(2) Equation (2) is a binomial expression where the first term corresponds to the reaction in the absence of added catalyst, and the second one to the nucleophile-catalyzed process. On the one hand, this expression predicts that for a reaction series where there is a set amount of added HClO 4 but a variable amount of nucleophile a linear plot of k obs vs. [X -] will be obtained (as shown in Figure 3).…”

Section: Hb Nitrosation In the Presence Of Nucleophilesmentioning

confidence: 99%

“…In the presence of nucleophiles the rate law given in Equation (2) for HB nitrosation can be obtained (for details, see Supporting Information, Section 6), where k NOX C -, k NOX Oare the reactivity constants of the carbanion and enolate forms of HB towards NOX, k NOX C is the reactivity constant of the carbon atom of the enol form, and K NOX is the equilibrium constant for the formation of the nitrosating agent. (2) Equation (2) is a binomial expression where the first term corresponds to the reaction in the absence of added catalyst, and the second one to the nucleophile-catalyzed process. On the one hand, this expression predicts that for a reaction series where there is a set amount of added HClO 4 but a variable amount of nucleophile a linear plot of k obs vs. [X -] will be obtained (as shown in Figure 3).…”

Section: Hb Nitrosation In the Presence Of Nucleophilesmentioning

confidence: 99%

“…This simultaneous catalysis constitutes the confirmation of two independent reactions on the carbon and oxygen atom of an enol (Scheme 2). Scheme 2. In contrast, the much higher acidity of HB compared to AcAc (pK a AcAc = 8.79 [2] and pK a HB = 4.04 [3] ) will give rise to a more complex reaction scheme, as the nitrosation of the carbanion enolate ion will constitute an additional reaction pathway. This additional operating mechanism will remarkably affect the kinetic behavior of the overall process, which is proposed to involve both enol and carbanion enolate forms of HB.…”

Section: Introductionmentioning

confidence: 99%

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Enol Nitrosation Revisited: Determining Reactivity of Ambident Nucleophiles

et al. 2009

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Enols are one of the most important types of ambident nucleophiles being widely used as reagents in organic chemistry. The relevance of enols has led to considerable interest in developing methods to determine the reactivity of their nucleophilic centers. In this sense, the mainstream literature works on this topic make use of a combination of overall rate constants together with the analysis of the reaction products. By knowing the product ratio it is possible to determine the ratio between the reaction rates on each site. Thus, the reactivity for each nucleophilic position can be obtained. This is a reliable approach as long as the isolation or in situ characterization of the reaction products can be carried out. In the case of unstable and/or interconvertible products where the use of identification techniques is not possible, an alternative methodology must be found. For that reason, our research group has developed a model that allows us to study and quantify separately the reaction rates of enol nucleophilic centers even if only one final reaction product is obtained. This model is based on the fact that nitrosation of enols shows well‐differentiated behavior depending on whether the reaction proceeds through the carbon or the oxygen atom. The present study provides insights into the ambident nature of enols as well as a methodology for determining the chemical reactivity of their nucleophilic centers. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

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“…The analysis of spectra clearly shows that DBM exists in the enol form with rather strong p-electron interaction between the enol ring and the phenyl rings. A spectrophotometric study of tautomeric properties of DBM in aqueous solution [15] (with ionic strength 0.1) at 25°C resulted in an equilibrium constant of enolization K = [enol]/[keto] = 6, which implies a strong preference of the enol form (86%).…”

mentioning

confidence: 99%

Tautomeric and conformational properties of dibenzoylmethane, C6H5–C(O)–CH2–C(O)–C6H5: gas-phase electron diffraction and quantum chemical study

2010

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Tautomeric and structural properties of dibenzoylmethane, C 6 H 5 -C(O)-CH 2 -C(O)-C 6 H 5 , have been investigated by gas-phase electron diffraction (GED) and quantum chemical calculations (B3LYP and MP2 approximation with different basis sets up to cc-pVTZ). Analysis of GED intensities resulted in the presence of 100(5)% enol tautomer at 380(5) K. The enol ring possesses C S symmetry with a strongly asymmetric hydrogen bond. The two phenyl rings are rotated with respect to the enol ring by 15.1(5.0) and 12.1(5.8)°. The experimental geometric parameters are reproduced very closely by the B3LYP/ cc-pVTZ method.

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The acidity and tautomerism of β-diketones in aqueous solution

Cited by 50 publications

References 13 publications

Probing keto–enol tautomerism using photoelectron spectroscopy

Probing keto–enol tautomerism using photoelectron spectroscopy

Enol Nitrosation Revisited: Determining Reactivity of Ambident Nucleophiles

Tautomeric and conformational properties of dibenzoylmethane, C6H5–C(O)–CH2–C(O)–C6H5: gas-phase electron diffraction and quantum chemical study

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