Polyethylene Glycols as Oligomeric Host Solvents: Applications to Oxidation and Reduction Reactions

Abstract

Polyethylene glycols (PEG) are oligomeric diols of the general formula HO(-CH₂-CH₂-O)_n-H, which are commercially available also under tne trade name of Carbowax. They can be regarded as protic solvents with aprotic sites of binding constituted by the oxyethylene units (-CH₂-CH₂-O-). A few inorganic salts as well as many organic substrates are soluble in low molecular weight PEG ($\overline {\text{M}}$ ranging from 200 to 600), which have been recently proposed as solvents for organic reactions¹. PEG were named “host” solvents, since they have the capability of forming complexes with some cations. This fact has been sustained by ¹H-N.M.R. studies² and isolation of a few solid complexes³. Further, PEG have a viscosity which is compatible with usual laboratory operations and offer a few advantages such as ready availability at low price, low vapour pressure and biodegradability.