Figure 11. Oligomerization and fragmentation reactions for oxidized oleic acid consistent with observation of trimer T1 and fragments F1, F2 by NMR spectroscopy. OA = oleic acid, R = C17H34.
Reaction of D1 with oleic acid to give T1 (Figure 11 ) corresponds to the rapid reaction of an alcohol with a carboxylic acid described by Ball et al. . The minor oxidized species contains F1, with a methylene carbon attached to oxygen (CH2-O) gives13C and 1H signals at 68 and 4.0 ppm, respectively. A methylene bonded to oxygen (CH2-O) does not exist in oleic acid. This paramount finding could be easily missed starting with acylglycerols, since they have these carbon types. Formation of such a chemical group, stemming from a primary alcohol, can only result from cleavage.
Fragment F1 is rarely proposed in the literature (e.g. Figure S20 ), which instead claims F2. Note that oxidative cleavage of epoxide M2 to give a primary alcohol does not occur since it would exhibit a1H CH2-O signal at 3.5 ppm. Instead, a1H CH2-O signal was observed at 4.0 ppm (Figure 8 ).