Identification, distribution and geochemical significance of four rearranged hopane series in crude oil

Abstract Four rearranged hopane series were simultaneously detected in oils from the Muglad Basin, one of several rift basins on the Central African Shear Zone (CASZ). The series are identified as having the structure of 17α(H)-diahopane (D series), 18α(H)-neohopane (Ts series), early eluting rearranged hopane (E series) and 21-methyl-28-norhopanes (Nsp series). The four rearranged hopane series exhibit strong positive correlations. The slope and intercept of the linear equation in plots of C29D/C29H vs C30D/C30H are 1.10 and 0.003 respectively, possibly implying identical biological origins and formation mechanisms. The relatively low slope ( Δ G ) calculated by density functional theory (DFT), the thermodynamic stabilities of C30 isomers follow the order C30D > C30H > C30E.