Mass spectrometry of fluorinated fatty acids in the seed oil of Dichapetalum toxicarium

The omega-fluoro fatty acids in the seed oil of Dichapetalum toxicarium have been characterized by gas chromatography-mass spectrometry of the picolinyl ester and 4,4-dimethyloxazoline derivatives. The picolinyl esters gave mass spectra that permitted determination of the positions of double bonds, and confirmed that the fluorine atom was on the terminal carbon in each instance. In contrast, it appeared that a rearrangement of the molecule occurred with the dimethyloxazoline derivatives which made it difficult not only to confirm the presence of the fluorine atom but also to establish its position. The mechanism of this rearrangement is discussed. It may be a characteristic of dimethyloxazoline derivatives of all omega-substituted fatty acids, not simply those containing fluorine atoms. By means of these techniques, a number of fatty acids were characterized in the oil, several for the first time, i.e. omega-fluoro-7-16:1, 9-16.1, 18:0, 9-18:1, 9,12-18.2, 20:0, 9-20:1 and 11-20:1, in addition to related non-fluorinated components. (C) 1998 Published by Elsevier Science Ireland Ltd. All rights reserved.