Mass spectral characterization of picolinyl and methyl ester derivatives of isomeric thia fatty acids

Abstract

Picoliiyl and methyl ester derivatives of all the isomeric thialaurates and thiastearates, together with some dithiastearates, have been characterized by gas chromatography/mass spectrometry. The picolinyl ester derivatives give simple electron impact mass spectra in which ions formed by cleavage at the sulphur atom and containing the sulphur atom are especially distinctive. The methyl ester derivatives have much more complex mass spectra, again dominated by ions formed by cleavage at the sulphur atoms, although aU possible fragments are seen. With both derivatives, the spectra are readily interpretable in terms of the positions of the sulphur atoms. The position of the sulphur atom can also have a marked effect on the abundance of the McLafferty rearrangement ion.

Structural Analysis of Fatty Acids

“…For small samples, a final clean-up step through small columns of silica or Florisil™ is usually necessary [60]. For small samples, a final clean-up step through small columns of silica or Florisil™ is usually necessary [60].…”

“…In this instance, the problem may have arisen through the use of thionyl chloride to prepare the picolinyl esters. Mass spectra of picolinyl esters of some synthetic thia [60,93] and selena [127) fatty acids, which have biochemical or pharmacological interest, have been published. 9-Hydroxystearic acid was identified in a seed oil by this means [190].…”

Derivatization in Mass Spectrometry– 3. Alkylation (Arylation)

“…75,76 They also appear to be useful for the determination of the position of sulfur in isomeric thialaurates, thiastearates and even dithiastearates. 77 Many EI mass spectra of picolinyl derivatives of various long-chain fatty acids are given on the internet. 44 Low-energy CID has been suggested for the structural analysis of some 3-picolinyl esters.…”

Synthesis and a study of the 13C NMR spectroscopic properties of positional isomers of some C18 acetylenic thia fatty esters

“…8 Skrede et al have reviewed the metabolism of thia fatty acids. 9 Our group have synthesized and studied spectroscopic and mass spectrometric properties of the positional isomers of the methyl thialaurate, [10][11][12][13] ten methyl dithiastearate isomers 14 and the corresponding sulfinyl and sulfonyl derivatives of methyl thialaurate. 15 In this paper, we describe the synthesis of a set of positional isomers of C 18 acetylenic thia fatty esters (5-8, Scheme 1) in an effort to study the effect of the sulfur atom on the chemical shifts of the carbon nuclei in the alkynyl chain of these thia fatty ester isomers by nuclear magnetic resonance spectroscopy.…”