Reactions in supercritical fluids. A case study of the thermodynamic solvent effects on a Diels-Alder reaction in supercritical carbon dioxide

The fundamental aspects of chemical reaction kinetics at near-critical conditions are discussed within the framework of transition state theory and the thermodynamics of critical phenomena for multicomponent systems. This discussion emphasizes the geometric analysis of Griffiths and Wheeler which describes the manner in which various thermodynamic properties behave on approaching mixture critical points for multicomponent systems. This analysis is used to explain experimental observations of the reaction kinetics for the Diels-Alder cycloaddition reaction of maleic anhydride with isoprene in supercritical CO2 at conditions near the critical point of CO2. The practical aspects of supercritical fluids as solvents for reacting systems are also discussed.