C₁₈-Isoprenoid Ketone in Recent Marine Sediment

Abstract

ISOPRENOID hydrocarbons, fatty acids and alcohols occur in ancient rocks, oil shales, young sediments and living organisms^1,2. During thermal alteration experiments on a recent marine sediment from Tanner Basin, Southern California continental shelf, we isolated a C₁₈-isoprenoid ketone, namely 6,10,14-trimethylpentadecan-2-one. Samples of sediment from the Tanner Basin were sealed in glass bombs and exposed to temperatures from 60° to 150° C for 7 d, 30 d and 60 d. The sediment was then extracted with benzene-methanol and the extract chromatographed on a silicic acid column. The ketone was found in both the heat-treated and untreated sediment. It was extracted with the fatty acid fraction which had been converted to methyl esters, and was separated with the other branched components by the urea adduction method. For comparative purposes, the C₁₈-isoprenoid ketone was also synthesized³. Analytical comparisons by gas-liquid chromatography, using two 5 foot × $\frac{1}{8}$ inch columns (3% OV 101 on 100/120 mesh ‘Gas Chrom’ Q and 3% DEGS on 100/120 mesh ‘Gas Chrom’ Z), showed the synthetic product to be identical to the sedimental ketone.