Effect of aqueous PEG or PPG solvents on reaction selectivity and Gibbs energies

Abstract

Low molecular weight polyethylene glycol (PEG 300)

Phase Diagrams for Liquid–Liquid Equilibrium of Aqueous Two-Phase System Containing Poly(ethylene glycol) (4000, 6000, or 10 000 g mol–1 + Sodium Hydrogen Sulfite + Water) at Different Temperatures

“…The most studied ATPS are those formed by mixing a polymer and salt, in particular polyethylene glycol, due to the advantageous characteristics these systems have as low cost of used materials, low viscosity phase, low toxicity, biodegradability, ability to reuse components of the mixture, and high ratio of water phase in formed ATPS. − In recent years, experimental data of phase equilibrium involving ATPS formed by polymer or copolymer + sodium sulfite or sodium hydrogen sulfite have been reported. The study of these new systems has been explored because of the particular properties of sulfites that incorporate desirable features to the ATPS with application prospects in separation processes in food industry .…”

Polyethylene glycol and solutions of polyethylene glycol as green reaction media

“…88 This solubility enhancement has been applied to aqueous synthesis in both Diels-Alder and S N 1 reactions. 88,116,117 Of particular interest, is the high solubility of some salts in PEG-400, such as 1.8 M CH 3 COOK, 2.1 M KI, 1.1 M KNO 3 , 0.25 M KCN, and 0.16 M K 2 Cr 2 O 7 . This has enabled the use of this medium in some homogeneous oxidation and substitution reactions resulting in high yields.…”

“…A few inorganic salts and many organic substrates are soluble in low molecular weight liquid PEG, and thus, they have been proposed as solvents for organic reactions. 71,88,116,117 PEGs have been termed ''host'' solvents 71 due to their ability to form complexes with metal cations as illustrated in Figs. 4 and 5.…”

“…[121][122][123] The similar small molecular weight liquid polypropylene glycols (PPG) 425 and 1000 have also found application in solvent substitution. 88,116,117,124,125…”

“…31,59,79,177,178 Recent extension of this technology has been directed toward application as green separation media 25 including, separation of organic hydrocarbon species 32,33,45 and metal ions. [34][35][36][37][38] However, both PEG and ABS have been largely ignored as ''green reaction media'' until recent papers indicated their application as new solvents for delignification of cellulose, [50][51][52][53][54][55] cyclic olefin oxidation, 56,57 polyoxometalate catalyzed aerobic oxidation, 68 S N 1, Diels-Alder, and enzymatic reactions, 88,116,117 and olefin catalytic oxidation to diols. 132 ABRE has three main characteristics: (1) phase separation benefiting separation of reactants and products, and providing a reaction driving force; (2) the PEG-rich top phase in PEGsalt ABS has organic solvent-like properties as a medium for reaction; (3) ABS components, PEG and metal salts, may be included in the form of PTCs 56,57 and metal-catalysts.…”