Infrared and nuclear magnetic resonance spectroscopic studies on the solvation of trimethylphosphate and dimethylmethylphosphonate

Abstract

Infrared and ³¹P NMR spectra have been studied for trimethylphosphate (TMP), dimethylmethylphosphonate (DMMP) and, less extensively, trimethylphosphorothioate (TMPS) in a range of pure and mixed solvents. The IR spectra for solutions in pure solvents cab be correlated with the acceptor numbers for these solvents. Analysis of mixed solvent systems comprising water or alcohol as one component shows that all these solutes form of mixtures of di- and tri-hydrates in pure water and of mono- and di- hydrates in methanol.

Shifts in the ³¹P resonance for TMP were small and showed no systematic correlation with solvent parameters. However, for the other two derivatives, these shifts were large and, for solutions in pure solvents, there were good correlations with the IR shifts. Using estimated concentrations for the different hydrogen-bonded species obtained from the mixed-solvent IR data, we have been able to reproduce shifts in the ³¹P resonances for DMMP (and TMPS) for a range of binary solvent systems.