DISTRIBUTION OF PENTACYCLIC TRITERPENOIDS IN GREEN RIVER OIL-SHALE KEROGEN

Pentacyclic triterpenoids released from Green River kerogen by a low temperature, mild, stepwise oxidative degradation using sodium dichromate in glacial acetic acid have been investigated by high resolution gas chromatography and computerized gas chromatography-mass spectrometry. Three series of stereoisomeric hopanoic acids (C30-C33) were found based on their αβ, ββ, and βα configurations. In addition, the following compounds were tentatively identified: 29,30-bisnorhopanoic acid, 30-norhop-22-one, 22,29,30-trinorhopan-21-one, 3-hopanone, and 3-gammacerone. The distribution of isomeric hopanoic acids supports previous suggestions of an extremely mild thermal history of Green River kerogen. Bonding of these triterpenoids to kerogen is likely to occur through the terminal positions (e.g. positions 3, 21, 22, 30, 31, etc.). The results also provide further evidence in favor of the microbiological origin of at least part of the organic matter in Green River oil shale kerogen. © 1990.