ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
Monte Carlo simulations using statistical perturbation theory (SPT) were applied to calculate the free energy, solvation enthalpy, and partial molar volume changes for transforming the solute methylamine to methanol in an aqueous solution of 264 water molecules. Using preferential, as well as random, sampling the calculated thermodynamic parameters were compared in the averaging phase after considering 1500 and 3000 K configurations. The relative free energy shows little variance after taking 1500 K configurations. The solvation enthalpy and the partial molar volume agree well with the experimental values after taking 3000 K configurations for methanol and 4500 K configurations for methylamine. There are 3.0 to 3.3 water molecules in the first hydration shells of the polar groups of the solutes with ∼2 of the waters involved in hydrogen bonds with methylamine and ∼2.4 hydrogen bonded to methanol. The calculated numbers of hydrogen bonds do not change after taking 1500 K configurations, and coordination numbers of the polar sites with water were stable after 3000 K. The similarity of the solution structures with the two different solutes suggests little difference in the solvation entropy in accordance with experiment.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.456852
