Thermodynamics of hydrogen bonding from molecular orbital theory: 2. Organics

Abstract

Hartree-Fock theory and density functional theory were used to compute the enthalpy and entropy changes of dimerization for a number of hydrogen-bonding compounds. In Part 1, the calculational methods and procedures use for the water dimer are described, and the results obtained are compared with those of uthers and with experimental estimates in the literature. Here, a variety of organic compounds that can self associate and/or cross associate are considered. The results obtained for the self-association of these compounds are compared with estimates obtained from various types of experimental data. The results are also used to examine the validity of group-contribution methods for hydrogen-bonding mixtures and to test a simple estimation procedure for cross dimerization that can reduce the number of calculations, such as those described here, that need to be done.

Capabilities, limitations and challenges of a simplified PC-SAFT equation of state

“…Estimation of SAFT parameters from "first principles" (ab-initio calculations, spectroscopy)-establishment of the physical meaning of the equation of state parameters (both those related to the "physical" and the "association" terms). Several attempts in this direction have been reported by Sandler and co-workers [46][47][48][49][50]. 2.…”

Association based equation of state for substances forming monomers, dimers and trimers

“…For this purpose, acetic acid was chosen, as the existing theories on the molecular arrangement of this substance suggest the formation of the monomers, dimers and trimers as the most dominant oligomers [10][11][12][13][14][15].…”

“…In this work, we report an exact closed-form expression for an association model that allows the formation of monomers, dimers and trimers. This type of association is seen in systems such as acetic acid [10][11][12][13][14][15] propanoic acid [12,15], methanol [16,17], etc. As a demonstration to the importance of using closed-form expressions, we use this monomer-dimer-trimer model to correlate the phase equilibria of acetic acid and compare these results to approximate techniques that one would employ when an exact closed-form expression is not available.…”

Quantum Chemistry in Engineering Thermodynamics

“…Based on these rules, Wolbach and Sandler 56,57 proposed the combining rule given by Equation (8.50) (Chapter 8), which is essentially Elliott's rule for the association strength. It is possible to eliminate one of the two association parameters of SAFT, but typically not both.…”