A study of hydrogen bonding in alcohol solutions using NMR spectroscopy

Abstract

A simple method is proposed to determine the Wilson constants from binary vapor-liquid equilibrium data. The method is based on a polynomial description of the variation of GE/RT with composition and finding the maximum value of the curve. The constants are determined by using a hand scientific calculator or a personal computer. Prediction of vapor compositions is as good or better than that obtained by complex optimization techniques.

Development of the AVEC model for associating mixtures using NMR spectroscopy

“…More detailed information on the solution property equations and their derivation is given by McNiel (1 987 i, Karachewski (1988), and Karachewski et al (1989).…”

“…Spectroscopic techniques allow one to probe solution behavior from a molecular perspective and have become increasingly common in recent years. Nuclear magnetic resonance in particular (Gutowsky and Saike, 1953; Foster and Fyfe, 1965;Bruno et al, 1983;Eckert et al, 1986;Karachewski et al, 1989) has been used quite successfully to probe the solution structure. In the NMR spectra, as the extent of hydrogen bonding changes so does the chemical shift of complex formation.…”

“…For example, the continuous linear association model (CLAM), used by Kretschmer and Wiebe (1954) and Renon and Prausnitz (1967) for alcohol-hydrocarbon mixtures, restricted complex formation to linear species only, all with equal probability of forming. The CLAM model, with only one chemical model parameter, is able to represent NMR solution behavior well in the concentrated alcohol region but in the more difficult dilute alcohol region, it is poorer (Karachewski et al, 1989). The CLAM model predicts activity coefficients well over the entire composition range, but it is not able to predict well the temperature dependence of the excess enthalpy (Karachewski et al, 1989).…”

“…The CLAM model, with only one chemical model parameter, is able to represent NMR solution behavior well in the concentrated alcohol region but in the more difficult dilute alcohol region, it is poorer (Karachewski et al, 1989). The CLAM model predicts activity coefficients well over the entire composition range, but it is not able to predict well the temperature dependence of the excess enthalpy (Karachewski et al, 1989).…”

“…Another example is the linear association with cyclic trimer (LACT) model (Karachewski et al, 1989), which was developed because of experimental spectroscopic evidence suggesting that the cyclic trimer is the first important complex to be formed in solution (Saunders and Hyne, 1958a,b;Tucker and Becker, 1973). The formation of the cyclic trimer is treated specially and has a unique equilibrium constant for complex formation assigned to it.…”