Use of low molecular weight oligomers as non-volatile reaction media
Very low molecular weight oligomers were prepared and evaluated as non-volatile reaction media. This paper reports the results of a preliminary feasibility study on the potential for oligomers to function as environmentally benign and cost-effective replacements for liquid solvents. The preparation and solvent efficacy are reported on two series of low molecular weight vinylpyrrolidone (VP) rich co-oligomers. The first series of oligomers employed 1-hexene as a 'soft' co-monomer, while the second series employed ethyl vinyl ether (EVE) as a 'soft' co-monomer. The 'soft' co-monomer was required to lower the Tg and Tm of the low molecular weight VP-rich oligomer so that a low viscosity liquid could be obtained at suitable reaction temperatures. This study determined the required amount of soft co-monomer and then evaluated the ability of the oligomers to solvate a variety of reactants. Selected oligomers from each series were employed as reaction media in aliphatic and aromatic nucleophilic substitutions, and in condensation reactions. Product yields were compared for both oligomers and for N-methylpyrrolidone (NMP), which is structurally similar to the VP repeat unit, and was used as a control solvent. Yields in oligomer solvents were similar to those obtained in NMP. Products were separated from the oligomers by distillation or aqueous extraction.
Use of low molecular weight oligomers as non-volatile reaction media.
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