The effect of hydrogen bonding on the diffusion of water in n-alkanes and n-alcohols measured with a novel single microdroplet method.
Abstract
While the Stokes-Einstein (SE) equation predicts that the diffusion coefficient of
a solute will be inversely proportional to the viscosity of the solvent, this relation
is commonly known to fail for solutes, which are the same size or smaller than the
solvent. Multiple researchers have reported that for small solutes, the diffusion
coefficient is inversely proportional to the viscosity to a fractional power, and
that solutes actually diffuse faster than SE predicts. For other solvent systems,
attractive solute-solvent interactions, such as hydrogen bonding, are known to retard
the diffusion of a solute. Some researchers have interpreted the slower diffusion
due to hydrogen bonding as resulting from the effective diffusion of a larger complex
of a solute and solvent molecules. We have developed and used a novel micropipette
technique, which can form and hold a single microdroplet of water while it dissolves
in a diffusion controlled environment into the solvent. This method has been used
to examine the diffusion of water in both n-alkanes and n-alcohols. It was found that
the polar solute water, diffusing in a solvent with which it cannot hydrogen bond,
closely resembles small nonpolar solutes such as xenon and krypton diffusing in n-alkanes,
with diffusion coefficients ranging from 12.5x10(-5) cm(2)/s for water in n-pentane
to 1.15x10(-5) cm(2)/s for water in hexadecane. Diffusion coefficients were found
to be inversely proportional to viscosity to a fractional power, and diffusion coefficients
were faster than SE predicts. For water diffusing in a solvent (n-alcohols) with which
it can hydrogen bond, diffusion coefficient values ranged from 1.75x10(-5) cm(2)/s
in n-methanol to 0.364x10(-5) cm(2)/s in n-octanol, and diffusion was slower than
an alkane of corresponding viscosity. We find no evidence for solute-solvent complex
diffusion. Rather, it is possible that the small solute water may be retarded by relatively
longer residence times (compared to non-H-bonding solvents) as it moves through the
liquid.
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https://hdl.handle.net/10161/3317Published Version (Please cite this version)
10.1063/1.3298857Publication Info
Su, Jonathan T; Duncan, P Brent; Momaya, Amit; Jutila, Arimatti; & Needham, David (2010). The effect of hydrogen bonding on the diffusion of water in n-alkanes and n-alcohols
measured with a novel single microdroplet method. J Chem Phys, 132(4). pp. 044506. 10.1063/1.3298857. Retrieved from https://hdl.handle.net/10161/3317.This is constructed from limited available data and may be imprecise. To cite this
article, please review & use the official citation provided by the journal.
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Show full item recordScholars@Duke
David Needham
Professor in the Department of Mechanical Engineering and Materials Science
Professor Needham has been at Duke since 1987 and over the years has developed many
collaborative and scholarly relationships across the campus and Medical School. He
holds Faculty and membership appointments as: Associate Professor of Biomedical Engineering;
Center for Bioinspired Materials and Material Systems; Center for Biomolecular and
Tissue Engineering; Duke Comprehensive Cancer Center; and the Duke Cancer Institute.
Internationally, he holds a joint appointment as Professor of T

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