Modeling Simple Alcohols in Two Dimensions
Barbara Hribar-Lee1*, and Ken A. Dill2
1Faculty of Chemistry and Chemical Technology, University of
Ljubljana, Aškerčeva 5, 1000 Ljubljana, Slovenia.
E-mail: barbara. hribar@fkkt.uni-lj.si
2Department of Pharmaceutical Chemistry, University of California,
San Francisco, California 94143-2240.
Absrtract
The alcohol-water mixtures were
studied within a two-dimensional model. The MB model was used for modeling water
and alcohol molecules were modeled as non-flexible chains consisting of
two-dimensional Lennard-Jones disks with the first disk having two
hydrogen-bonding arms. The model was explored using NPT Monte Carlo computer
simulation. The results were compared with the experimental thermodynamic
properties of methanol/water mixtures. The qualitative agreement was obtained
for the excess volume of mixing, but due to the surface/volume effects not
properly captured by two dimensional models, the excess enthalpy of mixing
cannot be represented correctly by this model. Further, we studied the transfer
of a single alcohol molecule into water, focusing on the trends exhibited by the
methanol, ethanol, propanol, n-butanol series. While small alcohol molecules
show the correct trend the flexibility of the alcohol molecules should be taken
into account to improve the agreement for higher alcohols.
Key words: MB model, alcohol/water mixtures, thermodynamics, Monte Carlo