Home About us Contact
|
Home About us Contact | ||
|
|
||
Chain Alkanes (chain + alkane)
Selected AbstractsAN UNUSUAL POLYUNSATURATED C-27 HYDROCARBON FROM THE MARINE DINOFLAGELLATE PYROCYSTIS LUNULAJOURNAL OF PHYCOLOGY, Issue 2001Article first published online: 24 SEP 200 Leblond, J. D.1 & Chapman, P. J.2 1Department of Biology, Middle Tennessee State University, Murfreesboro, TN 37132. 2US EPA (NHEERL), Gulf Ecology Division, 1 Sabine Island Dr., Gulf Breeze, FL 32561 Studies of the lipids of different algal species have revealed a diversity of fatty acids, sterols, and hydrocarbons, of which several are considered useful biomarkers, with potential for characterizing phytoplankton community composition. To extend this approach and characterize the lipids and lipid classes of laboratory-cultured marine dinoflagellates, a silicic acid fractionation system was developed to obtain compositional data for sterols and hydrocarbons of over forty species. In the course of this work, a neutral fraction obtained from a lipid extract of Pyrocystis lunula was found to contain an abundant quantity of a long-chain polyunsaturated hydrocarbon, along with previously reported keto-steranes. The hydrocarbon molecular weight (364) and retention time obtained by gas chromatography/mass spectrometry analysis suggested a C27 compound, which was confirmed by reduction (Adams catalyst) to give the straight chain alkane, n-heptacosane. The presence of eight double bonds was established by deuteration to give a product with molecular weight 396. While the positions of double bonds have not been established, the carbon number of this hydrocarbon and the number of double bonds strongly suggest formation by decarboxylation of the recently described, long-chain polyunsaturated C28 fatty acid shown to be a constituent of phospholipids. This hydrocarbon was not found in any other genus of the examined dinoflagellates, and appears to be one of the first identifications of a hydrocarbon in this class of algae. The function(s) of this compound in P. lunula is currently unclear. [source] The determination of n -alkanes in the cuticular wax of leaves of Ludwigia adscendens L.PHYTOCHEMICAL ANALYSIS, Issue 2 2004A. Barik Abstract An n -hexane extract of fresh, mature leaves of Ludwigia adscendens, containing a thin layer of epicuticular waxes, has been analysed for the ,rst time by TLC, IR and GC using standard hydrocarbons. The leaves contained 22 identi,ed long chain (C15,C36) n -alkanes, accounting for 74.27% of the hydrocarbons present, and an unknown number of unidenti,ed branched chain alkanes. The predominant n -alkane was C25 (11.02%), whilst C18 (7.62%), C20 (6.14%), C29 (5.36%) and C27 (5.29%) n -alkanes were moderately abundant: the C35 homologue was present only in minor amounts (0.22%). Copyright © 2004 John Wiley & Sons, Ltd. [source] Origin of the Silurian Crude Oils and Reservoir Formation Characteristics in the Tazhong UpliftACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 5 2010YANG Haijun Abstract: The Silurian stratum in the Tazhong uplift is an important horizon for exploration because it preserves some features of the hydrocarbons produced from multi-stage tectonic evolution. For this reason, the study of the origin of the Silurian oils and their formation characteristics constitutes a major part in revealing the mechanisms for the composite hydrocarbon accumulation zone in the Tazhong area. Geochemical investigations indicate that the physical properties of the Silurian oils in Tazhong vary with belts and blocks, i.e., heavy oils are distributed in the TZ47,15 well-block in the North Slope while normal and light oils in the No. I fault belt and the TZ16 well-block, which means that the oil properties are controlled by structural patterns. Most biomarkers in the Silurian oils are similar to that of the Mid-Upper Ordovician source rocks, suggesting a good genetic relationship. However, the compound specific isotope of n -alkanes in the oils and the chemical components of the hydrocarbons in fluid inclusions indicate that these oils are mixed oils derived from both the Mid-Upper Ordovician and the Cambrian,Lower Ordovician source rocks. Most Silurian oils have a record of secondary alterations like earlier biodegradation, including the occurrence of "UCM" humps in the total ion current (TIC) chromatogram of saturated and aromatic hydrocarbons and 25-norhopane in saturated hydrocarbons of the crude oils, and regular changes in the abundances of light and heavy components from the structural low to the structural high. The fact that the Silurian oils are enriched in chain alkanes, e.g., n -alkanes and 25-norhopane, suggests that they were mixed oils of the earlier degraded oils with the later normal oils. It is suggested that the Silurian oils experienced at least three episodes of petroleum charging according to the composition and distribution as well as the maturity of reservoir crude oils and the oils in fluid inclusions. The migration and accumulation models of these oils in the TZ47,15 well-blocks, the No. I fault belt and the TZ16 well-block are different from but related to each other. The investigation of the origin of the mixed oils and the hydrocarbon migration and accumulation mechanisms in different charging periods is of great significance to petroleum exploration in this area. [source] Aggregation of Dodecyl 1-Pyrenylmethyl Ether and Its Application in Structure-Polarity Relations of Aggregates,CHINESE JOURNAL OF CHEMISTRY, Issue 9 2006Da-Yong Sang Abstract The aggregation behavior of dodecyl 1-pyrenylmethyl ether was studied in dioxane-water mixture solvents by fluorescence techniques. The labeled pyrenyl group was effective in monitoring the polarity change of its environment during aggregation processes. Based on the structural effects such as chain-length effect, self-coiling effect, and branch-group effect on the polarity of the probe environment, the structure features of aggregates were discussed and have been used to interpret the effect of the structural features on the aggregates formed by three cholesteryl esters and three long chain alkanes. [source] | ||||||||||