USE OF MOLECULAR-DYNAMICS METHODS IN CONFORMATIONAL-ANALYSIS - GLYCOL - A MODEL STUDY

Different methods to calculate the potential of mean force using molecular dynamics have been used to estimate the difference in free energy between the gauche and trans conformations of the 1,2-ethanediol (glycol) molecule dissolved in water and in carbon tetrachloride. Results indicate that even in this simple model study simulations of many picoseconds are needed to obtain acceptably low estimated standard deviations. The calculated trans/gauche ratio in aqueous solution is larger than the observed one. Assuming that the solvent effects are more reliable than the intramolecular force field we used the observed ratio to predict an abundance of about 3% trans to be present in CCl4 solution. Details of the results for this solvent agree well with infrared spectra.