A review of the reactivity of organic compounds with oxygen-containing functionality in superheated water

Understanding the reactivity of organic molecules in pure superheated water is developing from studies aimed at explaining how organic matter (kerogen ) forms and then breaks down, in low temperature (< 150 degrees C) natural environments, into energy source materials. In natural systems where keroge ns are depolymerized to generate petroleum, superheated water is ubiquitous . Organic compounds, especially those with oxygen-containing functionality, can participate in reactions such as ionic condensations, additions, cleav ages and hydrolyses. These reactions are discussed with an awareness to the ir facilitation by changes in the chemical and physical properties of water as temperature increases. It is emphasized that these changes make the sol vent properties of liquid water at high temperature similar to those of pol ar organic solvents at room temperature, thus favoring ionic versus thermal free radical solution phase reactions with organic compounds. Examples ill ustrate that in this aquathermolysis chemistry, water can participate in on e or more roles: as a catalyst, reactant, and solvent. It is often not nece ssary to add acid, base, or other catalysts. We point out how an understand ing of the aqueous chemistry of a wide range of organic molecules may lead to environmentally friendly potential applications in areas as diverse as r ecycling of plastics, syntheses of chemicals, and generation of liquid fuel s from natural resource materials. (C) 2000 Elsevier Science B.V. All right s reserved.