The effect of paramagnetic shift reagents on the NMR spectra of oligomers containing ether linkages

Some polyethyleneglycols, oligomers of formaldehyde and copolymers of formaldehyde and ethylene oxide have been studied by high resolution NMR spectroscopy in the presence of tris-(dipivalomethanato)europium (Eu(DPM)3). It is shown that the magnitude of the paramagnetic shifts brought about by the Eu(DPM)3 is dependent on the distribution of europium between the various coordination centres in the chain. An assessment is made by means of Eu(DPM)3 of the relative basicity of the different coordination centres in the chains of the oligomers.