Transferable Potentials for Phase Equilibria. 8. United-Atom Description for Thiols, Sulfides, Disulfides, and Thiophene

Abstract

An extension of the transferable potentials for phase equilibria united-atom (TraPPE-UA) force field to thiol, sulfide, and disulfide functionalities and thiophene is presented. In the TraPPE-UA force field, nonbonded interactions are governed by a Lennard-Jones plus fixed point charge functional form. Partial charges are determined through a CHELPG analysis of electrostatic potential energy surfaces derived from ab initio calculations at the HF/6-31g+(d,p) level. The Lennard-Jones well depth and size parameters for four new interaction sites, S (thiols), S(sulfides), S(disulfides), and S(thiophene), were determined by fitting simulation data to pure-component vapor-equilibrium data for methanethiol, dimethyl sulfide, dimethyl disulfide, and thiophene, respectively. Configurational-bias Monte Carlo simulations in the grand canonical ensemble combined with histogram-reweighting methods were used to calculate the vapor-liquid coexistence curves for methanethiol, ethanethiol, 2-methyl-1-propanethiol, 2-methyl-2-propanethiol, 2-butanethiol, pentanethiol, octanethiol, dimethyl sulfide, diethyl sulfide, ethylmethyl sulfide, dimethyl disulfide, diethyl disulfide, and thiophene. Excellent agreement with experiment is achieved, with unsigned errors of less than 1% for saturated liquid densities and less than 3% for critical temperatures. The normal boiling points were predicted to within 1% of experiment in most cases, although for certain molecules (pentanethiol) deviations as large as 5% were found. Additional calculations were performed to determine the pressure-composition behavior of ethanethiol+n-butane at 373.15 K and the temperature-composition behavior of 1-propanethiol+n-hexane at 1.01 bar. In each case, a good reproduction of experimental vapor-liquid equilibrium separation factors is achieved; both of the coexistence curves are somewhat shifted because of overprediction of the pure-component vapor pressures.

Properties of water along the liquid-vapor coexistence curve via molecular dynamics simulations using the polarizable TIP4P-QDP-LJ water model

“…[1][2][3][4][5][6][7][8][9][10][11] Certainly, models can be successfully parametrized to reproduce target properties at various state points. Rather elegant work has been done to this effect by Chen and co-workers [12][13][14][15][16][17] leading to the fixed charge transferable potentials for phase equilibrium ͑TraPPE͒ force fields for fluid phase equilibria of a variety of polar and nonpolar species. Such force fields are able to reproduce the vapor-liquid coexistence curve and numerous properties of the bulk and vapor along the liquid-vapor binodal.…”

Prediction of the bubble point pressure for the binary mixture of ethanol and 1,1,1,2,3,3,3-heptafluoropropane from Gibbs ensemble Monte Carlo simulations using the TraPPE force field

“…[6][7][8][9][10][11][12][13][14] This force field derives its strength from the functional simplicity and transferability. To this extent, the parameterization follows a stepwise approach during which the interaction parameters for a given site are determined from fits to experimental vapor-liquid coexistence curves (spanning usually the entire liquid range).…”

Application of advanced oxidation processes for treatment of air from livestock and industrial facilities

“…Furthermore, removal efficiency of DMDS was the lowest among the three sulphur compounds at the same condition. Possibly it is related to the fact that 1) DMDS has a lower negative atomic charge on each of the sulphur atoms (-0.177 e) compared to the single sulphur atom in DMS (-0.300 e), so DMS could react faster with the positively charged hole [173][174][175], 2) the redox potential of DMS was 1.79 V versus a saturated calomel electrode (SCE) in CH 3 CN, which is higher than that of DMDS (1.15 V). Although it was in a different matrix, it could also indicate that the electron transfer of DMS is higher than that of DMDS [10], 3) singlet oxygen (Reaction 4) could add on the sulphide, which leads to the formation of thiosulfinate and thiosulfonate.…”