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.

Keywords: enthalpy of vaporization; hexafluoroisopropanol; mixtures; molecular dynamics simulations; quantum cluster equilibrium.

Figure 1

Radial distribution function, coordination number, and angular distribution function of the hydrogen bond for the system HFIP/acetone increasing the molar fraction of HFIP at 298.15 K with HFIP bond donor and acetone acceptor (left) or HFIP (right).

Figure 2

Radial distribution function, coordination number, and angular distribution function of the hydrogen bond for the system HFIP/methanol increasing the molar fraction of HFIP at 298.15 K with HFIP bond donor and MeOH acceptor (left), or MeOH donor and HFIP acceptor (right).

Figure 3

Radial distribution function, coordination number, and angular distribution function of the hydrogen bond for the system HFIP/methanol increasing the molar fraction of HFIP at 298.15 K, with HFIP donor and acceptor (left) or MeOH donor and acceptor (right).

Figure 4

Structures and relative populations of the most populated clusters of the neat systems acetone (a), HFIP (h), methanol (m) at 298.15 K.

Figure 5

Structures and relative populations of the most populated clusters of the system HFIP/acetone at the molar fraction of HFIP 0.2, 0.5, 0.8 at 298.15 K.

Figure 6

Structures and relative populations of the most populated clusters of the system HFIP/methanol at the molar fraction of HFIP 0.2, 0.5, 0.8 at 298.15 K.

Figure 7

Populations of neat acetone (a), MeOH (m), and HFIP (h) (from top to bottom) in the temperature range of 298.15‐338.15 K.

Figure 8

Populations of acetone (a), HFIP (h), MeOH (m) and mixed clusters at (from top to bottom) 0.2, 0.5, and 0.8 HFIP molar fraction, in the temperature range of 298.15–338.15 K.