Characterisation of highly branched isoprenoid thiophenesoccurring in sediments and immature crude oils

Abstract

A number of C20 and C25 highly branched isoprenoid thiophenes (HBIT) (i.e. thiophenes with 2,6,10-trimethyl-7-(3 -methylbutyl)dodecane and 2,6,10,14-tetramethyl-7-(3 -methylpentyl)pentadecane carbon skeletons) have been identified in sediments and immature oils from different geographical locations. Eight C20 and two C25 HBIT structural isomers were assigned on the basis of mass spectral characterisation, desulphurisation of isolated or mixtures of C20 and C25 HBIT and in some cases by comparison of mass spectral and relative retention time data with authentic compounds. Only a limited number of all theoretically possible isomers were present, indicating that these HBIT are probably formed by selective sulphur incorporation reactions into the widely occurring highly branched isoprenoid alkenes.