Reaction media engineering phase

The question of reproducibility and scale-up will always imply the question about reaction conditions. In addition, the reaction medium (phase) plays a much more important role for this kind of power input compared with classical reactions. Besides the molecular mass, reaction mixture polarity is essential for absorption of microwave power. Because dielectric constants are known for a few compounds only and, moreover, at near room temperature, more problems are predictable and require dose contact with neighboring disciplines, for example with electrical engineering. The primary literature reflects the incomplete nature of results from microwave-assisted reactions and processes, as it does for conventional syntheses. The dependence of reaction engineering on technical considerations is, however, greater for microwave-assisted reactions, so improved description of reaction conditions is crucial. 

The significance of this work is its identification of SC water as a medium which supports and enhances aqueous phase chemistry ordinarily observed at much lower temperatures. Fundamental studies of the reaction chemistry of biopolymer related model compounds described in this paper offer insights into the details of reaction mechanisms, and facilitate the choice of reaction conditions which enhance the yields of valuable products. Chemical reaction engineering in supercritical solvents, based on the ability to choose between heterolytic and homolytic reaction mechanisms with foreknowledge of results, holds much promise as a new means to improve our utilization of the vast biopolymer resource. 

Homogeneous reactions using transition metal catalysts can be engineered in ScCO medium for tuneable reaetion rates and seleetivity. It is possible to achieve deliberate control of the phase behavior, dissolution of reactants, recovery of products and catalyst by moderately changing the reaction temperature and pressure. 

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