Terpenoid Precursors of Hydrocarbons from the Gasoline Range of Petroleum

Abstract

2,6-Dimethyloctane and 2-methyl-3-ethylheptane were isolated from petroleum. These hydrocarbons which are present in relatively large amounts appear to be derived from the monoterpenoids.

Stable carbon isotope composition of monoterpanes in essential oils and crude oils

“…This suggests that 2,6-dimethyl octane may also be derived from biomass other than higher land plants, similar to retene, a well-established higher plant biomarker that has been detected in Lower Palaeozoic source rocks [13]. Therefore, more study has to be done to explore the origin of monoterpenoids despite the proposal by Simoneit [8] and Mair et al [14] that 2,6-dimethyl octane and 2-methy-3-ethyl-heptane can be derived from monoterpoids in higher land plants.…”

Crude Petroleum

“…Neopentane would be a logical product from a 1,1-dimethyl-3-,4-or 5-alkylcyclohexa-2,5-diene (the skeleton is common in natural products) by rupture ofthe two double bonds. MAIR [87] has proposed such a transformation of limonene to explain the abnormally high concentration of 2-methyl-3-ethyl-heptane that he has isolated from petroleum.…”

“…The presence of these alkanes in both terrestrial [189] and aquatic [190] plants is almost universal. The discovery of isoprenoid alkanes [103,104,87] in relatively high concentrations in petroleum has led to their widespread use as biological markers to indicate the presence of past life in a wide variety of geological situations [108]. With the identification of geranylgeraniol in plants [191], it would no longer appear always necessary to relate phytane and pristane directly to chlorophyll, or with the degradation of squalene [105]; indeed, it is probable that in time, free terpenoid precursors for the whole series of isoprenoid alkanes will be revealed in plants.…”

Mass Spectrometry in Organic Geochemistry

“…It is quite conceivable, however, that compounds of the isoprenoid type will be found which possess different substitution patterns, for example, structures derived from such precursors as squalene [115]. Indeed, compounds which do not bear a definite structural relationship to the isoprenoid class at all, but which might be derivable from more complex isoprenoidal precursors may be present in geological formations, as the recent find-ing [132] of 2-methyl-3-ethyl-heptane in petroleum, which could be derived from the cyclic monoterpene limonene, demonstrates. Correct identification of such hydrocarbons is essential, however, if any valid conclusions as to biological precursors or diagenetic history are to be drawn.…”