Occurrence, detection, and prevention of cyclization during hydrogenation of fatty oils

It has been shown that, under certain extreme conditions during catalytic hydrogenation of materials containing polyunsaturated fatty acids, o‐substituted benzene monocarboxylic acids (aromatic fatty acids = AFA) can be formed. Pure AFA were isolated from isomerized linseed oil, and their structure was elucidated from spectroscopic data. Final confirmation of the structure was obtained by direct synthesis. Quantitative determinations involved IR and NMR measurements of the urea non‐adduct forming fraction. In this way as little as 0.01% AFA can be detected. To provide a greater operational latitude in technical processing without formation of these compounds, a two‐stage modified hydrogenation process has been worked out.