Wednesday, October 17, 2007
The Proton Decoupled 31P NMR Spectrum of Triphenyl Phosphate
I was asked about the origin of the small peaks in the 31P NMR spectrum of triphenyl phosphate posted to this blog on October 4, 2007. The small peaks are 13C satellites. The phosphorus is coupled to the 13C in the ipso (J=7.47 Hz), ortho (J=4.98 Hz), meta (J=0.93 Hz) and para (J=1.32 Hz) positions on the aromatic rings. The coupling constants were measured in a high resolution 13C NMR spectrum. The figure below shows the proton decoupled 31P NMR spectrum with the couplings color coded. The satellites due to the meta and para couplings overlap. The displacement of the doublets is due to the isotope effect (see blog entry for September 13, 2007).