Communication: Stiffening of dilute alcohol and alkane mixtures with water

Ashbaugh, Henry S.; Barnett, J. Wesley; Saltzman, Alexander; Langrehr, Mae; Houser, Hayden

doi:10.1063/1.4971205

Cited by 18 publications

(23 citation statements)

References 26 publications

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“…Thus, by assessing the tetrahedrality of water molecules with L4WN an artificial decrease of the tetrahedrality is found. This has been previously observed 31,33,34 for different solutes, with a tetrahedrality enhancement starting at a distance from the solute, where water molecules have four water neighbors. Duboué-Dijon and Laage 38 found an increase of the LSI next to a hydrophobic solute consistent with that found here.…”

Section: Hydration Water Structuresupporting

confidence: 71%

“…The solvent excluded volume, connected to the formation of the solute's cavity, results in a reorganization of water's HB network. The nature of the former has been debated, with some studies indicating a tetrahedrality enhancement of some water molecules in the first coordination sphere of hydrophobic solutes and groups [30][31][32][33][34][35][36] , and others reporting opposite observations [37][38][39][40] . The enthalpy and entropy contributions associated with the reorganization of water's HB network to the hydration free energy have been shown to nearly compensate, thus not influencing the hydration free energy and, therefore, the solubility [41][42][43][44][45][46][47] .…”

Section: Introductionmentioning

confidence: 99%

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Solubility of Polar and Non-Polar Aromatic Molecules in Subcritical Water: The Role of the Dielectric Constant

Galamba

Paiva²,

Barreiros³

et al. 2019

Preprint

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Liquid water at temperatures above the boiling point and high pressures, also known as pressurized hot water, or subcritical water (SBCW), is an effective solvent for both polar and non-polar organic solutes. This is often associated to the decrease of water's dielectric constant at high temperatures, apparently allowing water to behave like an organic solvent. The decrease of the solubility at high pressures, in turn, is explained by a mild increase of the dielectric constant of water. Nevertheless, the relationship between the dielectric constant of water, hydration, and the solubility of polar and non-polar molecules in SBCW, remains poorly understood. Here, we study through molecular dynamics, the hydration thermodynamic parameters and the solubility of non-polar and polar aromatic model systems, for which a solubility increase in SBCW is observed. We show that the temperature dependence of the hydration free energy of the model non-polar solutes is nonmonotonic, exhibiting a solute size independent maximum at ~475 K, above which hydration becomes entropically favorable and enthalpically unfavorable. The monotonic increase of the solubility, separated here in hydration and vaporization or sublimation components of the pure liquid or solid solute, respectively, is, in turn, related to the temperature increase of the latter, and only to a minor extent with the decrease of the hydration free energy above ~475 K, via the hydration entropy. A solubility increase or decrease is also found at high pressures for different solutes, explained by the relative magnitude of the hydration and the vaporization or sublimation components of the solubility. For the model solid polar system studied, the hydration free energy increases monotonically with the temperature, instead, and the solubility increase is caused by the decrease of the sublimation component of the solubility. Thus, despite of the observed increase of the hydration free energy with pressure, related to the entropic component decrease, our results indicate that the dielectric constant plays no significant role on the solubility increase of non-polar and polar solutes in SBCW, opposite to the dielectric constant picture. The structure of water next to the solutes is also investigated and a structural enhancement at room temperature is observed, resulting in significantly stronger pair interactions between a water molecule and its third and fourth nearest water neighbors. This structural and energetic enhancement nearly vanishes, however, at high temperatures, contributing to a positive hydration entropy. <br>

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Section: Hydration Water Structuresupporting

confidence: 71%

Section: Introductionmentioning

confidence: 99%

Solubility of Polar and Non-Polar Aromatic Molecules in Subcritical Water: The Role of the Dielectric Constant

Galamba

Paiva²,

Barreiros³

et al. 2019

Preprint

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“…While not observed through neutron diffraction experiments(30-32) a tetrahedral enhancement of some water molecules next to small hydrophobic and amphiphilic molecules has been recently observed through molecular dynamics (17,(33)(34)(35)(36)(37)(38)(39)(40)(41), Raman scattering measurements with multivariate curve resolution (42,43) and infrared spectroscopy (44,45). Notice that any structural enhancement related to the reorganization of water upon insertion of the solute, while not contributing to the free energy (enthalpy-entropy compensation), still contributes to the hydration entropy and enthalpy.…”

Section: Introductionmentioning

confidence: 99%

Protein Denaturation Zero Entropy Temperature, and the Structure of Water Around Hydrophobic and Amphiphilic Solutes

Tamoliūnas¹,

Galamba

2020

Preprint

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The hydrophobic effect plays a key role in many chemical and biological processes, including protein folding. Nonetheless, a comprehensive picture of the effect of temperature on hydrophobic hydration and protein denaturation remains elusive. Here, we study the effect of temperature on the hydration of model hydrophobic and amphiphilic solutes through molecular dynamics aiming at getting in sight on the singular behavior of water concerning the zero entropy temperature TS and entropic convergence also observed upon protein denaturation. We show that, similar to hydrocarbons and proteins, polar amphiphilic solutes exhibit a TS, although strongly dependent upon solute-water interactions, opposite to hydrocarbons. Further, the temperature dependence of the hydration entropy normalized by the solvent accessible surface area is shown to be nearly solute size independent for hydrophobic but not for amphiphilic solutes, for similar reasons. These results are further discussed in the light of information theory (IT) and the structure of water around hydrophobic groups The latter shows that the tetrahedral enhancement of some water molecules around hydrophobic groups, associated with the reduction of water defects, leads to the strengthening of the weakest hydrogen bonds, relative to bulk water. However, a larger tetrahedrality is found in low density water populations, demonstrating that pure water has encoded structural information similar to that associated with hydrophobic hydration, consistent with IT assumptions. The source of the differences between Kauzmann's "hydrocarbon model" on protein denaturation and hydrophobic hydration is also discussed with relatively large amphiphilic hydrocarbons displaying a more similar behavior to globular proteins, than aliphatic hydrocarbons.<br>

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“…4. The physical properties of these liquids and experimental conditions are listed in Tables II-V in the Supplemental Material [22] and the references therein [31][32][33][34]. We evaluated the splashing parameter to obtain Oh Re 1.548 = 10 702.…”

Section: Resultsmentioning

confidence: 99%

Hidden prompt splashing by corona splashing at drop impact on a smooth dry surface

et al. 2020

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We present the experimental evidence of prompt splashing due to surface roughness at drop impact on a dry smooth surface, by suppressing corona splashing due to the surrounding gas. Prompt splashing occurs during a very early stage of the impact process, and it cannot be suppressed by reducing the gas pressure even to 0.8 kPa. We evaluate the conditions under which corona splashing hides prompt splashing at atmospheric conditions. We also demonstrate the importance of the distinction of two events, i.e., prompt splashing occurs and it can be clearly distinguished.

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Communication: Stiffening of dilute alcohol and alkane mixtures with water

Abstract: Assessing the thermodynamic signatures of hydrophobic hydration for several common water models

Cited by 18 publications

References 26 publications

Solubility of Polar and Non-Polar Aromatic Molecules in Subcritical Water: The Role of the Dielectric Constant

Solubility of Polar and Non-Polar Aromatic Molecules in Subcritical Water: The Role of the Dielectric Constant

Protein Denaturation Zero Entropy Temperature, and the Structure of Water Around Hydrophobic and Amphiphilic Solutes

Hidden prompt splashing by corona splashing at drop impact on a smooth dry surface

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