The properties and some key applications of solvents such as (1) supercritical fluids (SCFs), (2) gas-expanded liquids (GXLs) and organic-aqueous tunable solvents (OATS), (3) water at elevated temperature (WET), and (4) switchable solvents like reversible ionic liquids (RevILs) are discussed in this review. Each system offers a unique set of properties to enable alternative strategies for varied applications. These applications range from chemical transformations, product separation, catalyst recycling, nanomaterial processing, and CO₂ capture. For each application, however, the common thrust is to enable greener and sustainable solutions for chemical processes.

Switchable solvents are a unique class of solvents that were developed to facilitate both reaction and subsequent product separation. This mini review discusses two classes of switchable solvents: 1) piperylene sulfone and 2) one and two-component reversible ionic liquids.

An abiotic formation of meso- and d l-tartrates in 80% yield via the cyanide-catalyzed dimerization of glyoxylate under alkaline conditions is demonstrated. A detailed mechanism for this conversion is proposed, supported by NMR evidence and ¹³C-labeled reactions. Simple dehydration of tartrates to oxaloacetate and an ensuing decarboxylation to form pyruvate are known processes that provide a ready feedstock for entry into the citric acid cycle. While glyoxylate and high hydroxide concentration are atypical in the prebiotic literature, there is evidence for natural, abiotic availability of each. It is proposed that this availability, coupled with the remarkable efficiency of tartrate production from glyoxylate, merits consideration of an alternative prebiotic pathway for providing constituents of the citric acid cycle.