Gas chromatography-mass spectrometry of the stereoisomers of heterocyclic compounds.: Part 3.: Perhydro-4-thia-s-indacene

A gas chromatographic-mass spectrometric study of mixtures of the stereoisomers of perhydro-4-thia-s-indacene (PHTI) has been carried out. Separation has been accomplished on a column packed with graphitized thermal carbon black (GTCB) and on a capillary column of high efficiency. In addition to the known cis-syn-cis isomer, five novel diastereomers have been found. The stereospecificity of their fragmentation under electron impact appeared to be quite distinct and mass spectra (70 eV) of cis-cis, trans-cis and trans-trans conjugated isomers were distinguished. An important part in the structural elucidation of the novel isomers is played by molecular statistical calculations of the thermodynamic parameters of their adsorption on GTCB, which were performed on the basis of hypothetical molecular structures of these compounds optimized by molecular mechanics. Evidence for the existence of cis-cis isomers with the middle ring in a boat conformation obtained from these data is discussed.