Intra- and Intermolecular Hydrogen-Bonding Model and Its Application to 2-Alkoxyethanol Systems

Abstract

Intramolecular hydrogen bonding is known to be responsible for unusual phase behaviors such as liquid−liquid equilibria in polymer solutions and protein folding in biological systems. Results of experimental intra- and interbonded fraction data and molecular simulation have been interpreted using lattice statistics and perturbation theories. So far, however, few quantitative comparisons are reported with physical properties and phase equilibrium data of real systems. In this study, a more general derivation of statistics was developed for intra- and interbonding contributions based on Veytsman statistics, which was incorporated in physical contributions of a nonrandom lattice fluid theory to obtain a free energy model for real systems. The proposed model was applied to vapor pressures and densities of pure 2-alkoxyethanols and intra- and interbonded mole fractions and phase equilibria of 2-alkoxyethanol containing mixtures. Calculated results were found in close agreement with property data in the constraint of correlating inter- and intrabonded mole fractions, and deviations of calculated results with data were found similar to those without an intrabonding consideration.