¹³CMR analysis of methyl octadecenoates

Abstract

Abstract Carbon‐13 magnetic resonance spectra have been measured of methyl cis ‐ and trans ‐octadecenoates with the double bond positions 8, 9, 10, 11 and 12. The chemical shift of the allylic carbon atoms displays a large dependence on the stereochemistry of the double bond: δ ≈︁ 27.3 ppm for the cis and δ ≈︁ 32.6 for the trans configuration. The difference in chemical shift between the two ethylenic carbon absorptions increases significantly as the double bond approaches the ester group. Thus, the position as well as the configuration of the double bond in methyl 8‐ up to 12‐octadecenoates can readily be established by 13 CMR.