Sustainable Reactions in Tunable Solvents

Abstract

There are now available a variety of tunable solvents; these have been used extensively for extractions and in a variety of materials applications. Our focus has been to apply these techniques to chemical reactions to take advantage of the special properties available, primarily for sustainable technology, to create processes that are potentially more benign and more advantageous. We report here our work in using supercritical fluids, near-critical fluids, and gas-expanded liquids to couple organic reactions with separations. In this paper, we review applications involving improved transport, catalyst recycling, and product separation as well as the in situ generation of catalysts. Although such tunable solvents are in no way a panacea, they do offer the chemical community alternatives that can often be applied creatively to many reaction opportunities.

Carbon dioxide pressure induced heterogeneous and homogeneous Heck and Sonogashira coupling reactions using fluorinated palladium complex catalysts

“…The use of CO 2 as a miscibility switch was previously reported in several works of the groups of Eckert et al and Jessop et al using fluorous solvents and fluorinated metal complex catalysts [41][42][43][44]. These authors used bulk fluorous solvents and fluorous thin layers on the surface of a silica support; CO 2 pressure allows a catalyst-containing fluorous phase and a substrate-containing organic phase to merge into a single bulk liquid reaction phase.…”

“…The CO 2 pressure changes the partition of a fluorinated catalyst between a bulk organic phase and the silica-supported fluorous layer, in which the catalyst partitions into the organic reaction phase under pressurized CO 2 conditions. The features of those CO 2 -pressure tunable multiphase systems are demonstrated for reactions such as hydrogenation and epoxidation in the presence of gaseous reactants, as reviewed in a feature article [41]. The multiphase reaction media tunable by CO 2 pressure as well as temperature are expected to have practical merits and are still worth investigating for the process design of effective homogeneous catalysis and catalyst separation and recycling.…”

Reactivity and Dynamics at Liquid Interfaces

“…This process is used widely in organic synthesis, 615 in pharmaceutical and agrochemical industries, 5 in materials science 616 and in "green" chemistry applications. 614 In LLPTC, a water-soluble reactant is transferred, with the aid of a phase transfer catalyst, from an aqueous phase into an organic phase, where it reacts with a water-insoluble reactant. Once complete, the catalyst, which is typically a quaternary ammonium cation, transfers the product to the aqueous phase, and the catalytic cycle repeats.…”

Crystalline polymer decoration on multiwalled carbon nanotubes: MWCNT-induced P4VP periodic crystallization in CO2-expanded liquids

“…Gas expanded liquids (GXLs) are mixtures consisting of a liquid organic solvent and a near-critical gas such as CO 2 . These mixtures are currently being explored as potential replacements for pure organic solvents in chemical processing [10][11][12]. As such, they reflect a compromise between the use of conventional solvents, which are a major source of industrial pollution, and completely benign solvents like neat CO 2 , whose poor solvent qualities and high pressure requirements have limited its application.…”