Figure S18. Expanded 13C-1H HMBC NMR spectrum of oleic acid 210°C, 3h, air showing multiple-bond C-H correlations (over 3 covalent bonds). 13C signal of ester carbon correlates with 4.9 ppm (methine-O) and 4.0 ppm (methylene-O) 1H signals, while olefinic carbon shows no correlation with hydrogens of C-O carbons. Thus, carbons attached to oxygen are distant from olefinic carbon, ruling out alpha-hydroxyl olefins.