The dynamic behavior of a liquid ethanol―water mixture: a perspective from quantum chemical topology

Quantum Chemical Topology (QCT) is used to reveal the dynamics of atom-atom interactions in a liquid. A molecular dynamics simulation was carried out on an ethanol-water liquid mixture at its azeotropic concentration (X(ethanol)=0.899), using high-rank multipolar electrostatics. A thousand (ethanol)...

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Bibliographic Details
Published in:PCCP. Physical chemistry chemical physics (Print) 2011-05, Vol.13 (17), p.7821-7833
Main Authors: MEJIA, Sol M, MILLS, Matthew J. L, SHAIK, Majeed S, MONDRAGON, Fanor, POPELIER, Paul L. A
Format: Article
Language:English
Subjects:
Bonding
Chemistry
Computer simulation
Critical point
Electron density
Ethanol
Ethanol - chemistry
Ethyl alcohol
Exact sciences and technology
General and physical chemistry
Hydrogen Bonding
Liquids
Models, Molecular
Molecular Dynamics Simulation
Quantum chemistry
Quantum Theory
Water - chemistry
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Summary:Quantum Chemical Topology (QCT) is used to reveal the dynamics of atom-atom interactions in a liquid. A molecular dynamics simulation was carried out on an ethanol-water liquid mixture at its azeotropic concentration (X(ethanol)=0.899), using high-rank multipolar electrostatics. A thousand (ethanol)(9)-water heterodecamers, respecting the water-ethanol ratio of the azeotropic mixture, were extracted from the simulation. Ab initio electron densities were computed at the B3LYP/6-31+G(d) level for these molecular clusters. A video shows the dynamical behavior of a pattern of bond critical points and atomic interaction lines, fluctuating over 1 ns. A bond critical point distribution revealed the fluctuating behavior of water and ethanol molecules in terms of O-H···O, C-H···O and H···H interactions. Interestingly, the water molecule formed one to six C-H···O and one to four O-H···O interactions as a proton acceptor. We found that the more localized a dynamical bond critical point distribution, the higher the average electron density at its bond critical points. The formation of multiple C-H···O interactions affected the shape of the oxygen basin of the water molecule, which is shown in three dimensions. The hydrogen atoms of water strongly preferred to form H···H interactions with ethanol's alkyl hydrogen atoms over its hydroxyl hydrogen.
ISSN:1463-9076
1463-9084
DOI:10.1039/c0cp02869j