CONFINED-PYROLYSIS AS AN EXPERIMENTAL-METHOD FOR HYDROTHERMAL ORGANIC-SYNTHESIS

A closed pyrolysis system has been developed as a tool for studying th e reactions of organic compounds under extreme hydrothermal conditions . Small high pressure stainless steel vessels in which the ratio of se diment or sample to water has been adjusted to eliminate the headspace at peak experimental conditions confines the organic components to th e bulk solid matrix and eliminates the partitioning of the organic com pounds away from the inorganic components during the experiment. Confi ned pyrolysis experiments were performed to simulate thermally driven catagenetic changes in sedimentary organic matter using a solids to wa ter ratio of 3.4 to 1. The extent of alteration was measured by monito ring the steroid and triterpenoid biomarkers and polycyclic aromatic h ydrocarbon distributions. These pyrolysis experiments duplicated the h ydrothermal transformations observed in nature. Molecular probe experi ments using alkadienes, alkenes and alkanes in H2O and D2O elucidated the isomerization and hydrogenation reactions of aliphatic compounds a nd the competing oxidative reactions occurring under hydrothermal cond itions. This confined pyrolysis technique is being applied to test exp eriments on organic synthesis of relevance to chemical evolution for t he origin of life.