In 2005 Jiang and others reported the synthesis of benzoin using 1-butyl-3-methyl-methylimidazolium bromide (BMIMBr), a much safer catalyst than the cyanide anion traditionally used in this reaction. Literature methods for the synthesis of BMIMBr often report the formation of trace amounts of a yellow or brown-orange contaminant that remains after the washing and evacution of the ionic liquid. Heat is often used to drive BMIMBr formation. Such heating is thought to contribute to the coloring of the ionic liquid. Lastly, an ethyl acetate wash, which is known to reduce the product yield, is often used to remove residual 1-methylimidazole. The goal of this research was to develop a new undergraduate organic chemistry lab wherein high yields of colorless BMIMBr are achieved. It was found that a high yield of colorless BMIMBr could be achieved by simply combining 1-methylimidizole and 1-bromobutane in a flask and letting this mixture sit for a week. Purification did not require an organic wash of the ionic liquid formed and thus a higher product yield was acheived.

Simple no-heat, no-stir synthesis of butylmethylimidazolium bromide

251st National Meeting (2016)

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