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Polyethylene Glycol and Related Surfactants as Green Solvents for Chemical Synthesis

Traditional solvents in chemical synthesis are typically volatile, flammable and oftentimes toxic and harmful to the environment. One of the 12 Principles of Green Chemistry consequently concerns the replacement of traditional solvents with environmentally benign ones. One potential solvent that has been evaluated as “green solvent” is polyethylene glycol (PEG). Much less evaluated as green solvents are PEG related nonionic surfactants as defined in Scheme 1. As solvents, these may dissolve a wide variety of substances because of their amphiphilic structure.  Just like PEG, they too are environmentally benign substances because they possess low vapor pressure, are biodegradable and with respect to toxicity, there are no concerns because they are already widely used in industrial and household products. As a proof of concept, we have been able to carry out a particular Diels-Alder reaction in these surfactant media. The present focus is placed on characterizing these nonionic surfactants as solvents in comparison to PEG. Of particular concern are systems that are relevant for the synthesis of metal organic frameworks (MOFs), which are of interest to Professor Carly Reed. Aside from gaining a better fundamental understanding of PEG and related surfactants as solvents, it is hoped that these research efforts will stimulate synthetic chemists to also consider nonionic surfactants as a vital reaction medium.

Scheme 1 (three examples of PEG-related nonionic surfactants)

Scheme 1. a) PEG where, as an example, for PEG 200 the average molecular weight is 200 g·mol-1, b) CmEn, 3) CmEnPq, and d) Triton X-100. The subscript m indicates the number of carbon atoms in the alkyl chain (C), while n and q are the repetition units of ethylene oxide (E) and propylene glycol (P), respectively.

 

Ionic liquids in low dielectric media

Last Updated 8/13/18

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