Hydrothermal dehydration of aqueous organic compounds

Although mineral dehydration in hydrothermal and metamorphic processes is a commonly observed phenomenon, it is often stated that organic compounds will not dehydrate in the presence of an aqueous solution even at elevated temperatures and pressures. Both theoretical calculations and experimental measurements directly refute this paradigm. Results obtained in the present study indicate that increasing temperature tends to favor dehydration reactions among organic compounds in aqueous solution. Calculation of the thermodynamic properties for several aqueous organic dehydration reactions were conducted using equations, data, and parameters from Shock, and Helgeson (1990) and Shock (1992,1993a), together with additional data estimated in this study. Dehydration reactions which may proceed at elevated temperatures include amide formation from carboxylic acids and ammonia, ester formation from carboxylic acids and alcohols, and peptide formation from amino acids. Condensation of complex organic molecules may be energetically favored in hydrothermal solutions, which would greatly facilitate the ability of organisms to infiltrate high-temperature/pressure environments.