Monte Carlo structure simulations for tertiary-butyl alcohol solutions in water/acetonitrile solvents

Monte Carlo simulations for NpT (isobaric-isothermal) ensembles have been performed at T = 298 K and p = 1 atm for 1 molar tertiary-BuOH solutions in pure water, water:acetonitrile mixtures of 50:50, 30:70 molar ratios, and in pure acetonitrile. The simulated solution densities were within 1-3% of our measured densities. The solvation pattern remarkably changes upon the possibility of solute association/aggregation at finite concentration as compared to previous simulations for the infinitely dilute solution of t-BuOH. An increased readiness for solute association in the 1 molar t-BuOH solutions was observed with increasing acetonitrile fraction. In mixed solvents, the fraction of the Oalc-Halc···Owater solvation is larger than would proportionally follow from the solvent composition.