NMR-STUDY OF MALEATE (CIS)-FUMARATE (TRANS) ISOMERISM IN UNSATURATED POLYESTERS AND RELATED-COMPOUNDS

Unsaturated polyesters and dicarboxy diesters from maleic anhydride an d various diols were investigated by means of H-1 and C-13 nuclear mag netic resonance spectroscopy. The carbons of diol units were found to be sensitive to maleate/fumarate transformation, enabling the process to be followed in detail. The cis-trans isomerism of dicarboxy diester s was described and related to the structure of the corresponding diol s. The effects induced by the isomerism were examined separately for v arious carbons and, in the case of 1,2-propylene glycol, direct eviden ce was provided of the preference of CH over CH2 groups in promoting t he trans isomer. The results of the study on dicarboxy diesters along with data concerning the distribution of diol units along the chain we re utilized to interpret the isomerism of unsaturated mixed polyesters .