Study of Ionic Solvation and Determination of Solvation Numbers of Alkaline Earth Cations with HMPA in Nitromethane Using 1H NMR Technique

A proton NMR method for the drtermination of salvation numbers of alkaline earth cations with hexamethyl phosphoramide (HMPA) in nitromethane (NM) as diluents is described. The method is based on monitoring the resonance frequency of HMPA protons as a function of HMPA / metal ion molar ratio at constant metalion concentration. The average salvation number of cations,  , at any HMPA / metal ion ratio abtained from the NMR chemical shift-molar ratio data was plotted against the molar ratios values. The salvation numbers of each alkaline earth cation was determined from the limiting value of the corresponding  vs. molar ratio plot.