Oleic acid
Auto-oxidation of oleic acid was reported previously . “Clean”
observation of a methine carbon bonded to oxygen (-CHO-) drove us to
communicate the discovery, Figure 8 . 13C NMR
reveals on average, 40% of the starting carboxylic acid carbons are
converted into esters (Table 1 ). Two olefinic carbons and one
carboxylic carbon are lost per acyl chain. In correspondence, a major
species with one ester per methine bound to oxygen (CHO-) forms (T1
below). Previously, a dimer was suggested. But, to satisfy overall
oxidation, addition of oxygen to both olefinic carbons (C9,10) is
required. Otherwise, with only one ester bond (mono-acylation), net
oxidation does not occur (Figure S13 ).