The effect of maturation on the configurations of acyclic isoprenoid acids in sediments |
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| Authors: | AS Mackenzie RL Patience DA Yon JR Maxwell |
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| Institution: | Organic Geochemistry Unit, University of Bristol, School of Chemistry, Cantock''s Close, Bristol BS8 1TS, U.K. |
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| Abstract: | Within a variety of sedimentary rocks of differing maturity, the configurations of a suite of acyclic isoprenoid acids have been examined by gas Chromatographic (in a few cases also by combined gas chromatography-mass spectrometry) analysis of their diastereoisomeric methyl and (?)-menthyl esters. The samples include the Eocene Messel (Germany) and Green River (U.S.) shales, the Permian Irati shale (Brazil) and a number of Lower Toarcian shales from the Paris Basin. The isomer distributions show that isomerisation occurs at the chiral centres with increasing maturation (to increase the number of isomers) and that the rate of isomerisation increases for centres (C-2,C-3) closest to the carboxyl group. These results suggest that adsorption of the carboxyl group to a catalyst surface may control the isomerisation rates by way of access to the catalyst. |
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