Solvent effects on rates and equilibria: A practical approach

Buncel, Erwin; Wilson, H.K.

doi:10.1021/ed057p629

Cited by 14 publications

(8 citation statements)

References 38 publications

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“…Nevertheless, a variety of theories do exist, the most useful of them still being transition state theory (TST). − The main advantage of TST is the direct link of kinetics with thermodynamics, making it highly useful for studies of chemical reactivity in diverse media. The differences in reaction rates found for a reaction performed in different solvents can be straightforwardly linked to the differences in chemical potentials of the reactants (initial state, IS) and the activated complex in these solvents. − This activated complex (transition state, TS) is the structure corresponding to the highest Gibbs energy along the reaction path (excluding the reaction coordinate itself). Within TST, the problem of chemical reactivity therefore reduces to a thermodynamic problem.…”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Simulation of the Effect of Hydrophobic Cosolutes on the Neutral Hydrolysis of an Activated Ester

et al. 2004

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Citation for published version (APA):Rispens, T., Lensink, MF., Berendsen, HJC., & Engberts, JBFN. (2004). Molecular dynamics simulation of the effect of hydrophobic cosolutes on the neutral hydrolysis of an activated ester.We have studied, by means of molecular dynamics (MD) simulations, the effect of two hydrophobic cosolutes, tert-butanol (t-BuOH) and ethanol (EtOH), on the neutral hydrolysis of p-methoxyphenyl dichloroacetate (MPDA) in water. Shifts were calculated in a pre-equilibrium, defined as a spatial distribution of the reacting molecules satisfying specific geometric constraints. The criteria applied represent the configurations from which the reaction can take place (reactive conformation, RC). The shifts induced by the presence of cosolute, as determined from the simulations, correspond well to the experimentally found rate retardations. In accord with experiments, an almost linear correlation between the concentration of added cosolute and the logarithm of the rate constant was found. This is in agreement with a simple mechanistic model. The percentage of RCs in pure water was calculated to be ∼15%, complementing earlier work performed in this group (Lensink, M. F.;Mavri, J.; Berendsen, H. J. C. J. Comput. Chem. 1999, 20, 886), leading to a calculated rate constant of k calc ) 3.9 × 10 -3 s -1 (exptl: k obs ) 2.78 × 10 -3 s -1 ). The molecular structure of the RC was examined more extensively, investigating correlations between the positions of participating molecules.

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Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Simulation of the Effect of Hydrophobic Cosolutes on the Neutral Hydrolysis of an Activated Ester

et al. 2004

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“…Moreover, solvent polarity (implied by the solvent's dielectric constant), determines the strength of electrical interactions among species in the medium [43]. Solvation spheres of polar solvents can stabilize charged species and polar transition states by field effects [42,44], with solvent dipoles being directly involved in the reaction. This can lead to a reduction in the activation energy of the chemical step, leading to the complete ionization of donors and acceptors, hence kinetically enabling the reaction mechanism (for the redox step) leading to ionic CTC.…”

Section: (Tcnq)mentioning

confidence: 99%

Tetrathiafulvalene: A Gate to the Mechanochemical Mechanisms of Electron Transfer Reactions

2020

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This report describes aspects of our previous studies of the mechanochemical synthesis of charge transfer complexes of the electron donor tetrathiafulvalene, which are relevant to the use of laboratory X-ray powder diffraction for ex situ monitoring of mechanochemical reactions toward investigating their mechanisms. In particular, the reaction of tetrathiafulvalene and chloranil was studied under neat mechanochemical conditions and liquid-assisted grinding with diethyl ether (1 μL/mg). The product in both cases is the green tetrathiafulvalene chloranil polymorph and the mechanism of the redox reaction is presumably the same. However, while the kinetic profile of the neat mechanochemical synthesis was fitted with a second-order rate law, that of the overall faster liquid-assisted grinding reaction was fitted with the Ginstling-Brounshtein 3D diffusion-controlled model. Hence, the diffusional processes and mass transfer bringing the reactants together and separating them from products must be different. Diffraction measurements sensitive to crystalline phases and amorphous material, combined with in situ monitoring by spectroscopic techniques, will ultimately afford a better understanding of mechanochemical reaction mechanisms, a hot topic in mechanochemistry.

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“…It is apparent from the literature that the photodegradation quantum yields in ethanol and methanol are comparable [47]. Free energies of transfer (δG tr ) from alcohol or DMF to n-hexane were determined (Eqn 5) by measuring the distribution coefficient γ ( Table 5) of each dye at various temperatures in both phases [50,51]. The results for δG tr and other thermodynamic data calculated at 25 °C using Eqn 5 are reported in Table 6.…”

Section: Photochemical Experimentsmentioning

confidence: 99%

Electrochemical and photochemical reduction of a series of azobenzene dyes in protic and aprotic solvents

Sokołowska

Marcinek²,

Zielonka³

et al. 2003

Coloration Technology

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The electrochemical and photochemical reduction in ethanol of a series of azobenzene dyes containing tertiary amine groups has been investigated. It has been shown that the two mechanisms are of parallel importance and an explanation suggested using quantum chemical calculations (AM1, DFT). The solvation of these dyes in protic (methanol) and aprotic (dimethylformamide) solvents has also been studied and the effect of solvation on their electrochemical and photochemical reduction is discussed.

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Solvent effects on rates and equilibria: A practical approach

Abstract: Standard free energy-reaction coordinate diagrams are used routinely in a qualitative manner to rationalize solvent effects on rates and equilibria; however, they can lead to incorrect explanations of observed phenomena.

Cited by 14 publications

References 38 publications

Molecular Dynamics Simulation of the Effect of Hydrophobic Cosolutes on the Neutral Hydrolysis of an Activated Ester

Molecular Dynamics Simulation of the Effect of Hydrophobic Cosolutes on the Neutral Hydrolysis of an Activated Ester

Tetrathiafulvalene: A Gate to the Mechanochemical Mechanisms of Electron Transfer Reactions

Electrochemical and photochemical reduction of a series of azobenzene dyes in protic and aprotic solvents

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