Characterization of the molecular structure of cyclic alkenes isolated from Narragansett Bay sediment

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Sedimentary hydrocarbons in Narragansett Bay are composed of a large anthropogenic component, originating principally from inputs of petroleum products, and a smaller natural component, originating from both marine and terrigenous sources. The natural component is often dominated by a series of 25 and 30 carbon branched and cyclic alkenes, of which the origin and molecular structures are presently unknown. A chromatographic method has been developed for the isolation of these branched and cyclic alkenes from sedimentary lipid extracts. The compounds isolated have been subjected to catalytic hydrogenation and the products analyzed by gas chromatography/mass spectrometry (GC/MS). Comparison of the molecular weights of the intact alkenes and hydrogenated analogues, obtained from the GC/MS analysis, has established the number of double bonds and rings present in the individual compounds. Upon hydrogenation, two cyclic 30 carbon alkenes formed isomers which were easily separated by glass capillary gas chromatography. This information, in conjunction with the mass spectral fragmentation pattern observed for the hydrogenated compounds, has led to the formulation of a tentative structure for the cyclic portion of the hydrocarbon skeleton. © 1983.

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Marine Chemistry