Vapor pressure studies of hydrophobic association. Thermodynamics of fluorobenzene in dilute aqueous solution

Bernal, Pedro J.; Christian, Sherril D.; Tucker, Edwin E.

doi:10.1007/bf00646033

Cited by 11 publications

(17 citation statements)

References 11 publications

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“…The general expectation for hydrophobic interactions always had been that B 2 should be negative, indicating a net attraction, and increasing in strength with increasing temperature. Subsequent experiments for the non-spherical A = C 6 H 6 (benzene) 17,18 and for A = C 6 F 6 (perfluoro-benzene) 19 were consistent with the general expectation for hydrophobic interactions: this is a favorable and endothermic association, i.e., this is an entropy driven association. Though later results have revised that endothermicity for benzene association to smaller values, 20 simulation results on model spherical solutes in water agree with the prior expectation for hydrophobic interactions.…”

Section: Introductionsupporting

confidence: 68%

Role of attractive methane-water interactions in the potential of mean force between methane molecules in water

Asthagiri

Merchant

Pratt

2008

The Journal of Chemical Physics

136

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On the basis of a Gaussian quasichemical model of hydration, a model of non-van der Waals character, we explore the role of attractive methane-water interactions in the hydration of methane and in the potential of mean force between two methane molecules in water. We find that the hydration of methane is dominated by packing and a mean-field energetic contribution. Contributions beyond the mean-field term are unimportant in the hydration phenomena for a hydrophobic solute such as methane. Attractive solute-water interactions make a net repulsive contribution to these pair potentials of mean force. With no conditioning, the observed distributions of binding energies are super-Gaussian and can be effectively modeled by a Gumbel (extreme value) distribution. This further supports the view that the characteristic form of the unconditioned distribution in the high-epsilon tail is due to energetic interactions with a small number of molecules. Generalized extreme value distributions also effectively model the results with minimal conditioning, but in those cases the distributions are sufficiently narrow that the details of their shape are not significant.

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Section: Introductionsupporting

confidence: 68%

Role of attractive methane-water interactions in the potential of mean force between methane molecules in water

Asthagiri

Merchant

Pratt

2008

The Journal of Chemical Physics

136

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“…The osmotic second virial coefficient has so far been the only direct experimental check on the molecular theory of hydrophobic interactions between slightly soluble gases (A) in liquid water (3)(4)(5)(6). Here g AA (r) is the usual radial distribution function of AA pairs at infinite dilution.…”

mentioning

confidence: 99%

“…Because of low solubilities for solutes of interest, the necessary experiments are challenging. The initial comparisons between the only available molecular-scale theory, the Pratt-Chandler (PC) theory (7), and direct measurements of B 2 showed poor agreement (3)(4)(5)8).…”

mentioning

confidence: 99%

“…Of course, interactions that are repulsive on balance raise the osmotic pressure and are characterized by positive values of B 2 . A broad conclusion is that attractive and repulsive interactions can play conflicting roles (18) with the consequence that merely realistic simulation of a case of interest, e.g., CH 4 , might not provide transparent physical conclusions. In addition, the integrated quantity B 2 , particularly the R → ∞ limit, is a subtle target for molecular simulation calculations.…”

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confidence: 99%

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Molecular-scale hydrophobic interactions between hard-sphere reference solutes are attractive and endothermic

Chaudhari

Holleran

Ashbaugh

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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The osmotic second virial coefficients, B 2 , for atomic-sized hard spheres in water are attractive (B 2 < 0) and become more attractive with increasing temperature (ΔB 2 /ΔT < 0) in the temperature range 300 K ≤ T ≤ 360 K. Thus, these hydrophobic interactions are attractive and endothermic at moderate temperatures. Hydrophobic interactions between atomic-sized hard spheres in water are more attractive than predicted by the available statistical mechanical theory. These results constitute an initial step toward detailed molecular theory of additional intermolecular interaction features, specifically, attractive interactions associated with hydrophobic solutes.protein folding | self-assembly | Pratt-Chandler theory S olvent-mediated, noncovalent interactions within biomolecular structures are decisive for their stability and functionality over an extended range of conditions (1). Hydrophobic interactions-a principal category of noncovalent interactions in water-exhibit strong and characteristic temperature dependences (2). Molecular-scale theories of hydrophobic interactions are judged by their ability to capture those temperature dependences. Defensible theories might eventually illuminate a valid explanation and might find broader utility in modeling biomolecular structure and function.The osmotic second virial coefficienthas so far been the only direct experimental check on the molecular theory of hydrophobic interactions between slightly soluble gases (A) in liquid water (3-6). Here g AA (r) is the usual radial distribution function of AA pairs at infinite dilution. Because of low solubilities for solutes of interest, the necessary experiments are challenging. The initial comparisons between the only available molecular-scale theory, the Pratt-Chandler (PC) theory (7), and direct measurements of B 2 showed poor agreement (3-5, 8).Explanations for the discrepancy have been suggested (9-11), but the underlying disagreement has persisted (12). One explanation for this discrepancy focused on the differences between the actual interactions for accessible experimental cases and the hard-sphere solute-water interactions natural for the molecular theory. In this setting, direct high-resolution determination of hydrophobic interactions for the hard-sphere models treated by the theory would be a helpful step, but that has not been accomplished so far. The case of atomic-sized hardsphere solutes has not been treated specifically, mostly because hard-sphere models are inconvenient in available molecular dynamics simulations.These problems are of basic importance because hydrophobic interactions are acknowledged as the dominant factor that drives protein folding (13,14). Hydrophobic interactions are also expected to become more favorable with increasing temperature for physiological temperatures. Hydrophobic interactions can then be described as favorable for aggregation and endothermic at moderate temperatures. This is a primary conceptual puzzle that theories of hydrophobic effects should clarify.Summaries of the substa...

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“…7 Limited thermodynamic evaluation of hydrophobic interactions has been experimentally achieved for soluble, but more complex hydrophobic species with higher aqueous solubilities. 14,15 Those experiments set off a substantial modeling effort that has not untangled this complicated issue. 11 Here we show ( Fig.…”

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confidence: 99%

Communication: Direct observation of a hydrophobic bond in loop closure of a capped (–OCH $_2$2CH $_2$2–) $_n$n oligomer in water

Chaudhari

Pratt

Paulaitis

2010

The Journal of Chemical Physics

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The small r variation of the probability density P(r) for end-to-end separations of a –CH \documentclass[12pt]{minimal}\begin{document}$_2$\end{document}2CH \documentclass[12pt]{minimal}\begin{document}$_3$\end{document}3 capped (–OCH \documentclass[12pt]{minimal}\begin{document}$_2$\end{document}2CH \documentclass[12pt]{minimal}\begin{document}$_2$\end{document}2–) \documentclass[12pt]{minimal}\begin{document}$_n$\end{document}n oligomer in water is computed to be closely similar to the CH \documentclass[12pt]{minimal}\begin{document}$_4\cdots$\end{document}4⋯ CH \documentclass[12pt]{minimal}\begin{document}$_4$\end{document}4 potential of mean force under the same circumstances. Since the aqueous solution CH \documentclass[12pt]{minimal}\begin{document}$_4\cdots$\end{document}4⋯ CH \documentclass[12pt]{minimal}\begin{document}$_4$\end{document}4 potential of mean force is the natural physical definition of a primitive hydrophobic bond, the present result identifies an experimentally accessible circumstance for direct observation of a hydrophobic bond which has not been observed previously because of the low solubility of CH \documentclass[12pt]{minimal}\begin{document}$_4$\end{document}4 in water. The physical picture is that the soluble chain molecules carry the capping groups into aqueous solution, and permits them to find one another with reasonable frequency. Comparison with the corresponding results without the solvent shows that hydration of the solute oxygen atoms swells the chain molecule globule. This supports the view that the chain molecule globule might have a secondary effect on the hydrophobic interaction that is of first interest here. The volume of the chain molecule globule is important for comparing the probabilities with and without solvent because it characterizes the local concentration of capping groups. Study of other capping groups to enable x-ray and neutron diffraction measurements of P(r) is discussed.

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Vapor pressure studies of hydrophobic association. Thermodynamics of fluorobenzene in dilute aqueous solution

Cited by 11 publications

References 11 publications

Role of attractive methane-water interactions in the potential of mean force between methane molecules in water

Role of attractive methane-water interactions in the potential of mean force between methane molecules in water

Molecular-scale hydrophobic interactions between hard-sphere reference solutes are attractive and endothermic

Communication: Direct observation of a hydrophobic bond in loop closure of a capped (–OCH $_2$2CH $_2$2–) $_n$n oligomer in water

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