Organic compounds in meteorites—IV. Gas chromatographic-mass spectrometric studies on the isoprenoids and other isomeric alkanes in carbonaceous chondrites

Abstract

Nine homologous series of isomeric alkanes, in addition to the normal alkane series, have been identified by gas Chromatographic and mass spectrometric techniques in the hydrocarbon fractions from the extracts of six carbonaceous chondrites (Essebi, Grosnaja, Mokoia, Murray, Orgueil and Vigarano). Two of these series show isoprenoid structures corresponding to 2,6,10-trimethyl and 2,6,10,14-tetramethyl alkanes ranging from C 14 to C 18 and C 19 to C 21, respectively. The rest is made up of five series of monomethyl alkanes (2-, 3-, 4-, 5-, 6-methyl alkanes) and two of monocycloalkanes (cyclohexyl and cyclopentyl). The presence of members of the n-paraffin series between C 11 and C 26 inclusive was also confirmed by mass spectral data. The hydrocarbon content ranged from 6.7 to 82.8 ppm. Isoprenoids are present in all samples analyzed. Usually they show a major maximum at C 19 (pristane) and a secondary maximum at C 16 (methyl farnesane) with a minimum at C 17.