Guanidine/alcohol and Amidine/alcohol Switchable Solvent Mixtures
Hillary A. Huttenhower1, Lam Phan2, Daniel Chiu2, David J. Heldebrant2, Ejae A. John1, Xiaowang Li2, Pamela Pollet1, Charles A. Eckert3, Charles L. Liotta1, and Philip G. Jessop2. (1) School of Chemistry and Biochemistry, Georgia Institute of Technology, 311 Ferst Drive, NW, Atlanta, GA 30332-0400, (2) Department of Chemistry, Queen's University, Kingston, ON K7L 3N6, Canada, (3) School of Chemical & Biomolecular Engineering and Specialty Separations Center, Georgia Institute of Technology, 311 Ferst Drive, NW, Atlanta, GA 30332-0100
Organic solvents are a crucial part of chemistry on both a laboratory and an industrial scale. However, because solvents have very fixed properties, they often need to be removed and replaced between different steps of a reaction. This leads to an increase of economic cost and environmental impact for many processes. Developing a switchable solvent that can reversibly change its nature and properties at mild conditions would help solve this problem. Examples of solvents that consist of either a mixture of an amidine and alcohol or a guanidine and alcohol have been developed that form high polarity ionic liquids when exposed to CO2 at atmospheric pressure. Furthermore, these ionic liquids can be reversed back to a low polarity neutral form by exposure to nitrogen or mild heating. Such liquids have been used as a reaction medium utilizing their “built-in” facile separation.