PEG as a Green Replacement for Organic Solvents

Keywords Carbon dioxide Polyethylene glycol Biphasic solvent system Phase-transfer catalyst Surfactant Radical initiator 

ScC02 can serve as a particularly attractive mobile phase for organic reactions for several reasons [1] (1) it has a good solvent power for gas molecules (e.g., oxidation reaction involving oxygen), (2) its fluid properties simplify mass transport and separation from the product (no residues), and (3) as an inert gas, its 

Yang et al., Capture and Utilization of Carbon Dioxide with Polyethylene Glycol, 17 

The utility of the methodology for biphasic catalysis has been demonstrated with the RhCl (PPh3)3-catalyzed hydrogenation of styrene to ethyl benzene in PEG (MW = 900) (reaction conditions 30 bar H2, 50 bar C02, 40 °C and 19 h) [12], A total of five cycles are performed with one batch of catalyst/PEG solution, without replenishing either the catalyst or the PEG. The catalyst keeping active as 99 % conversion is found for all five cycles. 

The kinetic resolution of rac-1 -phenylethanol has been carried out using the biphasic system PEG1500/scC02. In a batch reaction an ideal conversion of 50.4 % can be achieved, affording (R)- (ee 98.1 %) and (S)- (ee 99.7 %) 

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