Results and Discussion
13C NMR spectroscopy identified the main species (above 1% mol C) formed after oxidation open to air (Table 1 ). Light molecular weight species were lost by evaporation with open containers. To verify oligomerization, e.g., formation of larger species, diffusivities of product molecules were measured (Table 2 ). These combined analyses of structure and size reveal the basic aspects of oil oligomerization, which proceed immediately following triglyceride hydrolysis.
NMR spectroscopy is very useful for studying molecules, especially when there is no signal overlap. Thus, the idea of avoiding glycerol-like species. Their role in vegetable oil polymerization will be considered in a subsequent work along with poly-unsaturated oils.13C NMR spectroscopy quantifies the most abundant species formed, using signals from key chemical groups: carboxylic acid, ester, olefin, glycerol, alkoxy, epoxide, methoxy, methylene and methyl (Table 1 ).
Table 1. Relative amounts of carbon nuclei (% mol)* in model molecules before and after auto-oxidation (210°C, 3h, air) determined by 13C NMR analysis.