Observation of a series of degenerate cyclic double, triple, and quadruple proton transfers in solid pyrazoles

Aguilar‐Parrilla, Francisco; Scherer, Gerd; Limbach, Hans−Heinrich; Foces-Foces, Maria de la Concepcion; Cano, F. H.; Smith, J. A. S.; Toiron, Catherine; Elguero, José

doi:10.1021/ja00050a055

Cited by 109 publications

(54 citation statements)

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“…192,193 Among the range of cluster sizes occurring in the normal vapor, the dimer is accessible to very high level quantum chemistry treatments; for large clusters one may look for viable alternative methods, such as density and hybrid functionals that we have investigated here. For structural and approximate energetic quantities, the BLYP density functional appears to be useful, although it exhibits disturbing deficiencies along the HF stretching and hydrogen transfer coordinates.…”

Section: Discussionmentioning

confidence: 99%

A critical analysis of electronic density functionals for structural, energetic, dynamic, and magnetic properties of hydrogen fluoride clusters

et al. 1997

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Section: Discussionmentioning

confidence: 99%

A critical analysis of electronic density functionals for structural, energetic, dynamic, and magnetic properties of hydrogen fluoride clusters

et al. 1997

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“…Depending on the substituents, one finds non-reactive chains or reactive cyclic dimers, trimers or even tetramers in which degenerate HH, HHH, or HHHH-transfers can take place [76,77] as depicted in Fig. 6.33 to 6.37.…”

Section: Applicationsmentioning

confidence: 99%

Single and Multiple Hydrogen/Deuterium Transfer Reactions in Liquids and Solids

Limbach

2006

Hydrogen‐Transfer Reactions

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OverviewIn this chapter, Arrhenius curves of selected single and multiple hydrogen transfer reactions for which kinetic data are available over a large temperature range are reviewed. The curves are described by a combination of formal kinetics of reaction networks and the one-dimensional Bell-Limbach tunneling model for each reaction step. The main parameters of this model are the barrier heights and barrier widths of the isotopic reactions, the tunneling masses, the pre-exponential factor and a minimum energy for tunneling to occur. This approach allows one to compare efficiently very different reactions studied in different environments and to prepare the kinetic data for higher-dimensional quantum-mechanical treatments. The first type of reactions discussed is concerned with those where the hydrogen bond geometries of the reacting molecules are well established and where kinetic data of the isotopic reactions are available over a large temperature range. Here, it is possible to study the relation between kinetic isotope effects and chemical structure. Examples are the tautomerism of porphyrin, of the porphyrin anion and related compounds exhibiting intramolecular hydrogen bonds of medium strength, and the solid state tautomerism of pyrazoles and of benzoic acid in cyclic associates. One main result is the finding of pre-exponential factors of the order of kT/h @ 10 13 s -1 , as expected by transition state theory for vanishing activation entropies. The barriers of multiple H-transfers are found to be larger than those of single H-transfers.The second type of reactions discussed refers mostly to liquid state solutions and involves major heavy atom reorganization. Here, equilibria between reactive and nonor less reactive molecular configurations may play a role. Several cases are discussed where the less reactive forms dominate at low or at high temperature, leading to unusual Arrhenius curves. These cases include examples from small molecule solution chemistry like the base-catalyzed intramolecular H-transfer in diaryltriazene, 2-(2¢-hydroxyphenyl)-benzoxazole, 2-hydroxy-phenoxyl radicals as well as an enzymatic system, thermophilic alcohol dehydrogenase. In the latter case, temperature dependent kinetic isotope effects are interpreted in terms of a transition between two regimes with different temperature independent kinetic isotope effects. 135Hydrogen-Transfer Reactions. Edited by

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“…Recently, the proton transfer in the solid state of these pyrazoles has been communicated (AguilarParrilla, Scherer, Limbach, Foces-Foces, Cano, Smith, Toiron & Elguero, 1992). The authors reported the structure of 3,5-diphenylpyrazole where they modelled the H atoms in a totally symmetrical system.…”

Section: Cah2n2]mentioning

confidence: 99%

Structure of [3,5-(C6H5)2C3H2N2]4. A 3,5-diphenylpyrazole tetramer linked by hydrogen bonds

Raptis¹,

Staples²,

King³

et al. 1993

Acta Crystallogr C

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Observation of a series of degenerate cyclic double, triple, and quadruple proton transfers in solid pyrazoles

Cited by 109 publications

References 0 publications

A critical analysis of electronic density functionals for structural, energetic, dynamic, and magnetic properties of hydrogen fluoride clusters

A critical analysis of electronic density functionals for structural, energetic, dynamic, and magnetic properties of hydrogen fluoride clusters

Single and Multiple Hydrogen/Deuterium Transfer Reactions in Liquids and Solids

Structure of [3,5-(C6H5)2C3H2N2]4. A 3,5-diphenylpyrazole tetramer linked by hydrogen bonds

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