Diels-Alder Reaction in Supercritical Fluids

A fluid is described as supercritical or subcritical if its temperature is above or below its critical temperature. Above the critical temperature the liquid and vapor phases are indistinguishable, the densities of the two phases become identical and the substance is described as a fluid, the physical properties of which are intermediate between those of a liquid and a gas [75]. 

Supercritical fluids (SCFs) have densities similar to those of liquids and a solvent power higher than that of gases, so that compounds which are insoluble in a fluid in ambient conditions become soluble in fluids under supercritical conditions [75]. 

Critical data for some substances, which are frequently used as solvents under supercritical conditions in chemical reactions, are reported [76] in Table 6.13. 

Although SCFs have been known for a long time, they have received attention in organic chemical research and industrial application only during the last two decades [76a, 77]. 

Today SCFs are used for natural product extractions, chromatographic separations, pollution prevention, material processing and as solvents for chemical reactions.[75-77] Chemical applications include catalysis, polymerization, enzymatic reactions and organic synthesis. 

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