Nuclear magnetic resonance in the study of unsaturated polyesters isomerization

The suitability of this method using proton spectra was tested in the observation of the isomerization of maleic acid polyesters. The determination is based on the different chemical shift of trans-hydrogen (3.26 tau) and cis-hydrogen (3.67 tau) in isomers of the dibutyl maleinate type. In the mixture, 1% of the isomer may be ascertained. The maximum relative deviation is 10% using at least a 20% resin solution. The method is quick and is suitable for laboratory use and field conditions. (M.K.)