| Abstract
| - Monte Carlo simulations have been performed to explore the solution structure of ethyl, isopropyl, isobutyl,and tertiary butyl alcohols in pure water, pure acetonitrile, and different mixtures of the two solvents. Theexplicit solvent studies in NpT ensembles at T = 298 K illustrate that the solute “discriminates” the solvent'scomponents and that the composition of the first solvation shell differs from that of the bulk solution. Sincethe polarizable continuum dielectric method (PCM) does not presently model the solvation of molecules withboth polar and apolar sites in mixed protic solvents, we suggest a direction for further program developmentwherein a continuum dielectric method would accept more than one solvent and the solute sites would besolvated by user-defined solvent components. The prevailing solvation model will be determined upon thelowest free energy calculated for a particular solvation pattern of the solute having a specific conformational/tautomeric state. Characterization of equilibrium hydrogen-bond formation becomes a complicated problemthat depends on the chemical properties of the solute and its conformation, as well as upon the varying natureof the first solvation shell. For example, while the number of hydrogen bonds to secondary and tertiaryalcohol solutes are nearly constant in pure water and in water−acetonitrile mixtures with at least 50% watercontent, the number of hydrogen bonds to primary alcohols gradually decreases for most of their conformationswhen acetonitrile content is increased. Nonetheless, the calculations indicate that O−H···Owater hydrogenbonds are still possible in a small fraction of the arrangements for the solution models with water content of30% or less. The isopentene solute does not form any observable hydrogen bonds, despite having an electron-rich, double-bond site.
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