CONFORMATIONAL BEHAVIOR OF TRIMETHYL PHOSPHATE STUDIED BY INFRARED-SPECTROSCOPY

The conformational behaviour of trimethyl phosphate was studied by inf rared spectroscopy in the liquid phase and as 1% solutions in a wide r ange of solvents. Variable temperature studies carried out in carbon d isulphide and liquid xenon solutions, and in the pure liquid phase, sh owed a reversal in the relative stability of the two conformers betwee n liquid xenon and carbon disulphide solutions. In liquid xenon soluti on the less polar conformer II is approximate to 1.8 kJ mol(-1) lower in energy, whereas in CS2 solution the more polar conformer I is appro ximate to 1.4 kJ mol(-1) more stable. In the pure liquid. the energy d ifference between the two conformers is similar to that in carbon disu lphide solution. Ab initio calculations predict that conformer II has C-3 symmetry with all the methoxy groups in the gauche configuration, whereas conformer I has C-1 symmetry with one trans and two gauche met hoxy groups.