KINETICS AND MECHANISM OF THE THERMAL ELIMINATION OF ALKENES FROM SECONDARY STANYL AND TRITERPENYL ESTERS - IMPLICATIONS FOR SEDIMENTARY PROCESSES

The liquid phase thermal decompositions of a secondary stanyl ester an d a secondary triterpenyl ester have been investigated in the temperat ure range from 275 degrees to 320 degrees C. First-order rate constant s have been measured and the activation energies and frequency factors for the processes determined. The reactions of naturally occurring se dimentary esters were also investigated by heating an oil shale at 295 degrees C in the presence of tetralin for various periods of time. An alysis of the reaction products showed that Delta(2)-sterenes and Delt a(3)-sterenes were produced at a rate consistent with their formation from secondary stanyl esters by a concerted reaction mechanism. The ex tent of reaction of secondary triterpenyl esters in a sedimentary sequ ence from the Gippsland Basin, Australia, was also investigated. A cor respondence was observed in the depth-calculated-for-reaction obtained using the laboratory-derived kinetic parameters and the measured depl etion of triterpenyl esters in the soluble organic matter in samples f rom the sequence. (C) 1997 Elsevier Science Ltd.