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

Abstract

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 atom-specific 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 measuredmore » negative excess entropy is a result of clustering or micro-immiscibility.« less

Authors:
;
Publication Date:
OSTI Identifier:
22657786
Resource Type:
Journal Article
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 144; Journal Issue: 19; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-9606
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ABSORPTION SPECTROSCOPY; BONDING; ENTROPY; ETHANOL; EXPERIMENTAL DATA; HYDROGEN; INTERACTIONS; LIQUIDS; METHANOL; MIXTURES; X-RAY SPECTROSCOPY

Citation Formats

Lam, Royce K., Smith, Jacob W., and Saykally, Richard J., E-mail: saykally@berkeley.edu. Communication: Hydrogen bonding interactions in water-alcohol mixtures from X-ray absorption spectroscopy. United States: N. p., 2016. Web. doi:10.1063/1.4951010.
Lam, Royce K., Smith, Jacob W., & Saykally, Richard J., E-mail: saykally@berkeley.edu. Communication: Hydrogen bonding interactions in water-alcohol mixtures from X-ray absorption spectroscopy. United States. https://doi.org/10.1063/1.4951010
Lam, Royce K., Smith, Jacob W., and Saykally, Richard J., E-mail: saykally@berkeley.edu. Sat . "Communication: Hydrogen bonding interactions in water-alcohol mixtures from X-ray absorption spectroscopy". United States. https://doi.org/10.1063/1.4951010.
@article{osti_22657786,
title = {Communication: Hydrogen bonding interactions in water-alcohol mixtures from X-ray absorption spectroscopy},
author = {Lam, Royce K. and Smith, Jacob W. and Saykally, Richard J., E-mail: saykally@berkeley.edu},
abstractNote = {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 atom-specific 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.},
doi = {10.1063/1.4951010},
url = {https://www.osti.gov/biblio/22657786}, journal = {Journal of Chemical Physics},
issn = {0021-9606},
number = 19,
volume = 144,
place = {United States},
year = {2016},
month = {5}
}

Works referencing / citing this record:

X-ray absorption signatures of hydrogen-bond structure in water-alcohol solutions
journal, September 2018


Structures, intermolecular interactions, and chemical hardness of binary water–organic solvents: a molecular dynamics study
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Dilution of whisky – the molecular perspective
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Intramolecular dehydration of biomass-derived sugar alcohols in high-temperature water
journal, January 2017


Water fluctuation in methanol, ethanol, and 1-propanol aqueous-mixture probed by Brownian motion
journal, December 2018


The Stokes-Einstein relation in water/methanol solutions
journal, June 2019


Bubble Rise Velocity and Surface Mobility in Aqueous Solutions of Sodium Dodecyl Sulphate and n-Propanol
journal, November 2019