p<i>K</i><sub>a</sub> Values of Amines in Water from Quantum Mechanical Calculations Using a Polarized Dielectric Continuum Representation of the Solvent

and, Bernd Kallies; Mitzner, R.

doi:10.1021/jp962708z

Cited by 135 publications

(117 citation statements)

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“…+ distance is calculated to be 1.20 Å, which is similar to the previous result from MP2/6-311+g(2d,2p) calculation yielding a symmetric hydrogen bond of length 2.38 Å with the proton located 1.19 Å from each oxygen. 43 In H + (CH 3 OH) 3 , the excess proton was located on the central methanol. In contrast to the neutral methanol cluster, the linear chain was the most stable conformation.…”

Section: Resultsmentioning

confidence: 99%

“…1 Examples 1-24 include carboxylic acids, [7][8][9]11,14,[17][18][19] alcohols, 11 thiols, 11 phenols, 21 pyrone derivatives, 12 amines, 3 imidazoles, 5,24 hydrated transition metal cations, 2 transition metal complexes, 16 phosphoranes, 22 and DNA (RNA) bases. 6,15,23 Recent applications are extended to the evaluation of pK a values of 1) intermediate species that are not easily measured experimentally, 22 2) weak organic acids with high pK a values, 13 which cannot be measured experimentally in aqueous phase, and 3) molecules having multiple protonation sites.…”

Section: Introductionmentioning

confidence: 99%

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Calculation of the Solvation Free Energy of the Proton in Methanol

Hwang¹,

Chung²

2005

Bulletin of the Korean Chemical Society

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The solvation free energy of proton in methanol was calculated by B3LYP flavor of density functional calculations in combination with the Poisson-Boltzmann continuum solvation model. In order to check the adequacy of the computation level, the free energies of clustering in the gas phase were compared with the experimental data. The solvents were taken into account in a hybrid manner, i.e. one to five molecules of methanol were explicitly considered while other solvent molecules were represented with an implicit solvation model.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Calculation of the Solvation Free Energy of the Proton in Methanol

Hwang¹,

Chung²

2005

Bulletin of the Korean Chemical Society

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“…However, this initial unstable product can react further to N-hydroxybenzamide. 22,23 The zwitterionic form of hydroxylamine is not present in detectable amounts, 20,23 practically excluding the Odeprotonated hydroxylamine as the nucleophile.…”

Section: From Base-catalysed Hydrolysis To Nucleophilic Substitutionmentioning

confidence: 99%

General‐base catalysed hydrolysis and nucleophilic substitution of activated amides in aqueous solutions

Buurma

Blandamer

Engberts

2003

J of Physical Organic Chem

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General-base catalysed hydrolysis and nucleophilic substitution of activated amides in aqueous solutions Buurma, NJ; Blandamer, MJ; Engberts, Jan; Buurma, Niklaas J. Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. ABSTRACT: The reactivity of 1-benzoyl-3-phenyl-1,2,4-triazole (1a) was studied in the presence of a range of weak bases in aqueous solution. A change in mechanism is observed from general-base catalysed hydrolysis to nucleophilic substitution and general-base catalysed nucleophilic substitution. A slight tendency is also observed for the more hydrophobic general bases to show higher reactivity towards 1a. Aspartame is an effective nucleophile, possibly because nucleophilic substitution is subject to intramolecular general-base catalysis. A general conclusion derived from the present results is that unexpected rate effects can only be rationalised provided that the detailed reaction mechanisms are well understood. Copyright  2003 John Wiley & Sons, Ltd.KEYWORDS: hydrolysis; changes in mechanism; general-base catalysis; general-acid catalysis; nucleophilic substitution INTRODUCTIONThe hydrolysis reaction of the activated amide 1-benzoyl-3-phenyl-1,2,4-triazole (1a) is general-base catalysed (Scheme 1). 1In highly aqueous solutions, the concentration of water is sufficiently high for water to act (detectably) as both a general base and a nucleophile. Hence, in the absence of other general bases, the water-catalysed (i.e. pHindependent) hydrolysis is the sole reaction. In the presence of sufficiently basic cosolutes, the watercatalysed reaction is unimportant. More basic cosolutes are much more effective catalysts for hydrolysis than water. Consequently, despite the relatively low molality of added general bases, the general-base catalysed hydrolysis pathway competes with the water-catalysed pathway. It is stressed that even though in the watercatalysed reaction the second water molecule in the activated complex (i.e. B = H 2 O, Scheme 1) acts as a general base, a distinction is drawn between the watercatalysed reaction and general-base catalysed reaction.Increased basicity of cosolutes usually leads to a concomitant increase in nucleophilicity. This increase in nucleophilicity provides an alternative reaction pathway: nucleophilic attack on the carbonyl functionality, followed by loss of the (substituted) 1,2,4-triazole leaving group (Scheme 2).In this mechanism, the nucleophilic water molecule is replaced by a stronge...

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“…Interesting are the DFT studies with emphasis on the simulation of solvent. [4][5][6] All these methods involve sophisticated computational method and the variations of Gibbs energy calculation schemes.…”

Section: Introductionmentioning

confidence: 99%

Simple Method for the Estimation of pKa of Amines

Juranic¹

2014

Croat. Chem. Acta

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pK_a Values of Amines in Water from Quantum Mechanical Calculations Using a Polarized Dielectric Continuum Representation of the Solvent

Cited by 135 publications

References 30 publications

Calculation of the Solvation Free Energy of the Proton in Methanol

Calculation of the Solvation Free Energy of the Proton in Methanol

General‐base catalysed hydrolysis and nucleophilic substitution of activated amides in aqueous solutions

Simple Method for the Estimation of pKa of Amines

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pKa Values of Amines in Water from Quantum Mechanical Calculations Using a Polarized Dielectric Continuum Representation of the Solvent

Cited by 135 publications

References 30 publications

Calculation of the Solvation Free Energy of the Proton in Methanol

Calculation of the Solvation Free Energy of the Proton in Methanol

General‐base catalysed hydrolysis and nucleophilic substitution of activated amides in aqueous solutions

Simple Method for the Estimation of pKa of Amines

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pK_a Values of Amines in Water from Quantum Mechanical Calculations Using a Polarized Dielectric Continuum Representation of the Solvent