Dynamical aspects of mixing schemes in ethanol–water mixtures in terms of the excess partial molar activation free energy, enthalpy, and entropy of the dielectric relaxation process

Sato, Takaaki; Chiba, Akio; Nozaki, Ryusuke

doi:10.1063/1.477956

Cited by 128 publications

(131 citation statements)

References 38 publications

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“…The increase in the relaxation time upon cooling reflects the slowingdown process of the rearranging cooperative motion. The addition of the water to the ethanol slightly reduces the acoustic relaxation times, consistent with the change in the dielectric relaxation times [15]. Considering the consistent temperature dependence of both relaxation times shown in Fig.6, the origin of the acoustic relaxation process and the dielectric relaxation process probed by the two experimental methods seems to be the same.…”

Section: Discussionsupporting

confidence: 59%

“…For comparison, the dielectric relaxations of pure ethanol and ethanolwater mixture (20%) from Ref. [15], measured by the time domain reflectometry, are also shown. The increase in the relaxation time upon cooling reflects the slowingdown process of the rearranging cooperative motion.…”

Section: Discussionmentioning

confidence: 99%

“…However, multiple interaction between ethanol and water molecules is expected to make some structural changes to the chainlike clusters of ethanol [15], which may induce the change in the hydrodynamic fluctuations of self-associating fluids. One example is the high-temperature dispersion observed in the 1-octanol [16].…”

Section: Discussionmentioning

confidence: 99%

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Angular Dispersion-type Nonscanning Fabry-Perot Interferometer Applied to Ethanol-water Mixture

Ko¹,

Kojima²

2009

Journal of the Optical Society of Korea

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The angular dispersion-type non-scanning Fabry-Perot was applied to an ethanol-water mixture in order to investigate its acoustic properties such as the sound velocity and the absorption coefficient. The scattered light from the mixture was analyzed by using the charge-coupled-device area detector, which made the measurement time much shorter than that obtained by using the conventional scanning tandem multi-pass Fabry-Perot interferometer. The sound velocity showed a deviation from ultrasonic sound velocities at low temperatures accompanied by the increase in the absorption coefficient, indicating acoustic dispersion due to the coupling between the acoustic waves and some relaxation process. Based on a simplified viscoelastic theory, the temperature dependence of the relaxation time was obtained. The addition of water molecules to ethanol reduced the relaxation time, consistent with dielectric measurements. The present study showed that the angular dispersiontype Fabry-Perot interferometer combined with an area detector could be a very powerful tool in the real-time monitoring of the acoustic properties of condensed matter.

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Section: Discussionsupporting

confidence: 59%

Section: Discussionmentioning

confidence: 99%

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Angular Dispersion-type Nonscanning Fabry-Perot Interferometer Applied to Ethanol-water Mixture

Ko¹,

Kojima²

2009

Journal of the Optical Society of Korea

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“…[33][34][35] Dielectric relaxation and nuclear magnetic resonance spectroscopies support the clustering explanation while also revealing reduced liquid mobility. [36][37][38][39][40][41] Using Raman spectroscopy, Ben-Amotz et al have concluded that the observed clustering in alcohol-water mixtures is a result of random, rather than hydrophobic, interactions. 42,43 In contrast, some femtosecond midinfrared spectroscopy experiments have shown that water surrounding the aliphatic groups of the alcohols displays significantly slowed dynamics relative to the bulk, lending support to the model in which the measured negative excess entropy is attributed to water forming clathrate-like structure around the hydrophobic groups of the alcohols.…”

Section: -17mentioning

confidence: 99%

Communication: Hydrogen bonding interactions in water-alcohol mixtures from X-ray absorption spectroscopy

Lam

Smith

Saykally

2016

The Journal of Chemical Physics

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While methanol and ethanol are macroscopically miscible with water, their mixtures exhibit negative excess entropies of mixing. Despite considerable effort in both experiment and theory, there remains significant disagreement regarding the origin of this effect. Different models for the liquid mixture structure have been proposed to address this behavior, including the enhancement of the water hydrogen bonding network around the alcohol hydrophobic groups and microscopic immiscibility or clustering. We have investigated mixtures of methanol, ethanol, and isopropanol with water by liquid microjet X-ray absorption spectroscopy on the oxygen K-edge, an atomspecific probe providing details of both inter-and intra-molecular structure. The measured spectra evidence a significant enhancement of hydrogen bonding originating from the methanol and ethanol hydroxyl groups upon the addition of water. These additional hydrogen bonding interactions would strengthen the liquid-liquid interactions, resulting in additional ordering in the liquid structures and leading to a reduction in entropy and a negative enthalpy of mixing, consistent with existing thermodynamic data. In contrast, the spectra of the isopropanol-water mixtures exhibit an increase in the number of broken alcohol hydrogen bonds for mixtures containing up to 0.5 water mole fraction, an observation consistent with existing enthalpy of mixing data, suggesting that the measured negative excess entropy is a result of clustering or micro-immiscibility. Published by AIP Publishing. [http://dx

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“…Even though molecules like methanol and water can be mixed over the whole concentration range, the methyl groups still tend to cluster to some degree in methanol solutions 26 . Dielectric relaxation measurements of a number of alcohol/water mixtures have revealed mixing to be a complex function of alcohol concentration [27][28][29][30] . Molecular simulation of such mixtures reproduces most features of these mixtures at least qualitatively 31,32 .…”

Section: Introductionmentioning

confidence: 99%

Organic molecules on the surface of water droplets – an energetic perspective

Hub

Caleman

Spoel

2012

Phys. Chem. Chem. Phys.

100

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The solubility of organic molecules is a well established property, founded on decades of measurements, the results of which have been tabulated in handbooks. Under atmospheric conditions water droplets may form containing small amounts of other molecules. Such droplets typically have a very large area to volume ratio, which may shift the solvation equilibrium towards molecules residing on the droplet surface. The presence of organic molecules on droplet surfaces is extremely important for reactivity -it is well established that certain chemical reactions are more prevalent under atmospheric conditions than in bulk. Here we present a thermodynamic rationalization of the surface solvation properties of methanol, ethanol, propanoic acid, nbutylamine, diethyl ether, and neopentane based on potential of mean force (PMF) calculations -we have previously demonstrated that an energetic description is a very powerful means of disentangling the factors governing solvation (Caleman et al., Proc. Natl. Acad. Sci. U.S.A. 108 (2011) 6838-6842). All organic molecules investigated here are preferentially solvated on the surface of the droplets rather than in the inside, yet the magnitude of surface preference may differ by orders of magnitude. In order to dissect the energetic contributions that govern surface preference, we decompose the PMF into enthalpic and entropic components, and, in a second step, into contributions from water-water and solute-water interactions. The analysis demonstrates that surface preference is primarily an enthalpic effect, but the magnitude of surface preference of solutes containing large apolar groups is enhanced due to entropy. We introduce an analysis of the droplet PMFs that allows one to extrapolate the results to larger droplets. From this we can estimate the solubility of the solutes in water droplets, demonstrating that the solubility in droplets can be orders of magnitude larger than in bulk water. Our findings have implications for understanding the process of electrospray ionization, an important technique in biological mass spectrometry, since our work strongly suggests that in equilibrium biomolecules would be adsorbed on the droplet surface as well.

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Dynamical aspects of mixing schemes in ethanol–water mixtures in terms of the excess partial molar activation free energy, enthalpy, and entropy of the dielectric relaxation process

Cited by 128 publications

References 38 publications

Angular Dispersion-type Nonscanning Fabry-Perot Interferometer Applied to Ethanol-water Mixture

Angular Dispersion-type Nonscanning Fabry-Perot Interferometer Applied to Ethanol-water Mixture

Communication: Hydrogen bonding interactions in water-alcohol mixtures from X-ray absorption spectroscopy

Organic molecules on the surface of water droplets – an energetic perspective

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