Transferable Potentials for Phase Equilibria–United Atom Description of Five- and Six-Membered Cyclic Alkanes and Ethers

While the transferable potentials for phase equilibria–united
atom (TraPPE–UA) force field has generally been successful
at providing parameters that are highly transferable between different
molecules, the polarity and polarizability of a given functional group
can be significantly perturbed in small cyclic structures, which limits
the transferability of parameters obtained for linear molecules. This
has motivated us to develop a version of the TraPPE–UA force
field specifically for five- and six-membered cyclic alkanes and ethers.
The Lennard-Jones parameters for the methylene group obtained from
cyclic alkanes are transferred to the ethers for each ring size, and
those for the oxygen atom are common to all compounds for a given
ring size. However, the partial charges are molecule specific and
parametrized using liquid-phase dielectric constants. This model yields
accurate saturated liquid densities and vapor pressures, critical
temperatures and densities, normal boiling points, heat capacities,
and isothermal compressibilities for the following molecules: cyclopentane,
tetrahydrofuran, 1,3-dioxolane, cyclohexane, oxane, 1,4-dioxane, 1,3-dioxane,
and 1,3,5-trioxane. The azeotropic behavior and separation factor
for the binary mixtures of 1,3-dioxolane/cyclohexane and ethanol/1,4-dioxane
are qualitively reproduced.