Hydrogen Bonding and Vaporization Thermodynamics in Hexafluoroisopropanol‐Acetone and ‐Methanol Mixtures. A Joined Cluster Analysis and Molecular Dynamic Study

Abstract

Binary mixtures of hexafluoroisopropanol with either methanol or acetone are analyzed via classical molecular dynamics simulations and quantum cluster equilibrium calculations. In particular, their populations and thermodynamic properties are investigated with the binary quantum cluster equilibrium method, using our in-house code Peacemaker 2.8, upgraded with temperature-dependent parameters. A novel approach, where the final density from classical molecular dynamics, has been used to generate the necessary reference isobars. The hydrogen bond network in both type of mixtures at molar fraction of hexafluoroisopropanol of 0.2, 0.5, and 0.8 respectively is investigated via the molecular dynamics trajectories and the cluster results. In particular, the populations show that mixed clusters are preferred in both systems even at 0.2 molar fractions of hexafluoroisopropanol. Enthalpies and entropies of vaporization are calculated for the neat and mixed systems and found to be in good agreement with experimental values.

Error quantification of phase transition quantities from cluster weighting calculations

“…Methanol is therefore the only system investigated for which both approaches overestimate the experimental vaporization enthalpy. Such an overestimation of the vaporization enthalpy has already been observed before 46 and might be due to the reason that methanol molecules aggregate to small clusters in the gas phase 63 which is not properly sampled by the QCE 0 -calculations.…”

“…As already mentioned in the last section, this is most likely due to the fact that the gas phase of the polar alcohols is not described properly by a QCE 0 calculation. 46 In summary, when considering the standard QCE approach, the deviations from the experimental vaporization entropies are within a range of 1.97 (2.5 %) to 29.92 J mol −1 K −1 (27.4 %). Considering the Clausius-Clapeyron approach on the other hand results in deviations of 3.14 (3.9 %) to 25.54 J mol −1 K −1 (23.4 %).…”

“…with β xv being the exclusion volume expansion coefficient and b 0 xv is the base of the intercept. 46 The resulting translational partition function is now given as follows:…”

Conformer Weighting and Differently Sized Cluster Weighting for Nicotine and Its Phosphorus Derivatives

“…Up to now, the QCE theory has been applied to various systems, including water, ,, aqueous solutions, , and even ionic liquids . Recently, the mRRHO approach was employed for the calculation of improved enthalpies and entropies of vaporization, and the cluster weighting was applied for the calculation of vibrational circular dichroism spectroscopy. , In addition, the bQCE method was applied for the evaluation of activity coefficients , as well as for the investigation of dissociation processes − and hydrogen bond networks …”

The Ionic Product of Water in the Eye of the Quantum Cluster Equilibrium

“…Instead of scanning all possible combinations of a mf and b xv on a coarse grid as in earlier studies, the current version of Peacemaker [34,35,37] features an implementation of the downhill simplex algorithm [40] which speeds up the calculations tremendously [41] while also increasing the accuracy of the parameter optimization. Here, a mf and b xv were optimized within a range of 0.0 to 2.0 J m 3 mol −2 and 0.5 to 2.0, respectively, so as to minimize the deviations of the computed density at room temperature and of the phase transition temperature from their respective experimental values.…”