RESUMO
The addition of Pr(fod)3 i.e. tris(1,1,1,2,2,3,3-heptafluoro-,7-dimethyl 1-4,6-octanedionato) praseodymium, to trilinolein has been found to induce a difference in the chemical shifts of the absorptions from the acids on the alpha- and beta positions. At 220 MHz this was observed up to 18 carbon atoms along the chain. Decoupling of the alkenyl protons at 100 MHz enabled the absorptions from the skipped methylene groups to be used to determine the position of linoleate and linolenante chains in triglycerides.
Assuntos
Ácidos Graxos Insaturados/análise , Triglicerídeos , Espectroscopia de Ressonância Magnética , Métodos , Conformação Molecular , Relação Estrutura-AtividadeRESUMO
The carbon magnetic resonance spectra of many fatty acid methyl esters with cis and trans double bonds and triple bonds at various positions and in many different combinations have been investigated. The influence of the ester group on double and triple bonds in the fatty acid chain depends strongly on the positions of these bonds. For a given position the influence is constant, even if one or more other double or triple bonds are present. Together with the evaluated chemical shift parameters for the effects of double and triple bonds on each other, complete assignments are possible and spectra of various types of unsaturated esters can be predicted with high accuracy (+/- 0.1 ppm).