SUPERCRITICAL CARBON-DIOXIDE AS REACTION MEDIUM - EXAMINATION OF ITS SOLVENT EFFECTS IN THE NEAR-CRITICAL REGION

The consequence of the compressible properties of supercritical carbon dioxide on the Diels-Alder reaction between isoprene and methyl acrylate in the solvent is discussed on the basis of IR spectroscopic data. The transition activation volume of the reaction and the excess number of solvent molecules about the reacting species have been thermodynamically determined using the E(T)(30) value of supercritical carbon dioxide. They are significantly changed with density in the near-critical region, where the activation volume gets greatest negative and the excess number of solvent molecules are greatly increased. These results strongly suggest the state of aggregation of solvent molecules about the reacting species on the Diels-Alder reaction in the vicinity of the critical point. The relationship between the activated complex-solvent intermolecular forces and the isomer distribution of the Diels-Alder reaction in supercritical carbon dioxide is examined.