Correlation of ~1H NMR chemical shift for associated systems by local composition model and two-liquid theory
The ~1H NMR chemical shift is widely used to investigate the microstructure and thermodynamics of associated solution.Based on the concept of local composition and two-liquid theory, a semi-empirical physical local composition model was proposed to correlate ~1H NMR chemical shift of associated solution.The model contained two parameters denoting the intermolecular interaction energy.The associated systems including self-associate and cross-associate mixtures were selected and investigated with the model.The results showed that the model could be used to correlate the ~1H NMR chemical shift of various associated mixtures.Assuming that the model parameters do not change with temperature, then the chemical shift of the same binary system at a different temperature is predicted.Seven associated mixtures were tested as examples to study the influence of temperature on the mixture chemical shift, and the deviations of prediction were almost of the same order of magnitude with those of correlation.