This work showcases the utility of switchable materials. Included are a switchable room-temperature ionic liquid, a switchable solvent, a switchable heterogeneous catalyst system, and a switchable gel. First, the switchable ionic liquid 2-butyl-1,1,3,3-tetramethylguanidium methylcarbonate is fully investigated. Its use in a complete chemical process (including reaction, separation, reformation, and recycle) is demonstrated with several reactions. Furthermore, its potential use for bitumen separation and purification and SO2 capture/isolation are discussed, and preliminary data is presented. Next, piperylene sulfone (PS), a switchable solvent, is synthesized and fully characterized. Anionic nucleophilic substitution reactions were performed in PS, the products were isolated in high yields, and then the PS was reformed for reuse. Then, we designed an immobilized fluorous microphase system that uses F-MonoPhos to induce high enantioselectivities as a switchable heterogeneous catalyst system. Finally, stable reversible polyethyleimine-CO2 gels have been synthesized with 1-octanol. Our findings indicate that PEI-1200/octanol/CO2 gels have potential as a possible drug carrier matrix for transdermal delivery applications.

This work seeks to develop new solvents for environmentally benign chemical synthesis. Switchable solvents are a new class of compounds that change properties upon the application of some stimulus such as heat, UV light, or pH. We have developed the use of a new solvent, thiirane oxide, that has chemical properties similar to DMSO. Thiirane oxide, however, undergoes facile decomposition to two gases at temperatures above 100 C, which is much lower than the temperature required for removing DMSO. Thus we have a solvent with excellent solvation properties, but with a built-in switch for easier removal. However, thiirane oxide leaves behind sulfurous products which make the reverse reaction to reform the solvent unfeasible. We are also developing the use of another solvent, piperylene sulfone, which is expected to have good solvent properties, yet with decomposition products that can be reacted to reform the solvent. This thesis also details the work to date on piperylene sulfone. Gas-expanded liquids (GXLs) also show promise as a new reaction medium. In order to design solvent systems that take full advantage of this medium, we desire to understand the microstructure of these fluids. To that end, we are using cage reactions to probe solute-solvent and solvent-solvent interactions at the molecular level. This thesis discusses the current research on using cage reactions to probe the structure of GXLs.

The work in this thesis couples reactions with separations through the use of switchable and tunable solvents. Tunable solvents are mixed solvents which can be easily altered to afford conditions optimal for reaction or separation. Switchable solvents are solvents that can be switched when desired to alter their properties affording conditions suitable for separation. Other studies are of the reaction of CO2 with the amidine base DBU, and an NMR study of solvent-to-solute nuclear Overhauser effects. These examples constitute a marriage of reaction environment with separation environment, significantly, to the benefit of both.

Environmentally benign alternatives for solvents and catalysts are essential for the development of sustainable chemical processes. Toward this end, we focused our research on the design of novel solvents and catalysts that reduce the environmental impact of these important materials. In this research, we develop switchable and tunable systems that couple reaction and separation to ease the processing requirements for product isolation and catalyst recovery. The switchable solvents use a ¡°switch¡± to transition from non-volatile, polar, aprotic solvents to volatile gases that can be easily separated. This allows us to facilitate reactions within the solvent and then enable easy separation through activation of the switch. We have used these materials for numerous reaction applications, including difficult reactions involving highly immiscible compounds. We also extended the work to acid-catalyzed reactions, in which we can avoid wasteful neutralization processes that are often associated with homogeneous acid catalysis. The tunable solvents use carbon dioxide pressure to ¡°tune¡± into desired solvent properties. We enable this through the dissolution of carbon dioxide into organic solvents, which generates gas-expanded liquids with solvent properties highly dependent on the carbon dioxide pressure. We can use this effect to couple homogeneous reaction with heterogeneous separation, allowing for recovery of expensive catalysts and ligands. In this work, we assess the possibilities of using liquid polyethylene glycol in the tunable systems, studying the phase behavior and industrial applications.