Sweeteners for Ion Liquids

The anions of artificial nonnutritive sweeteners may help to enhance the "green" nature of room-temperature ionic liquids, suggest chemists at the University of South Alabama, Mobile.

The team prepared a family of 15 salts consisting of organic cations and the anions of saccharin or acesulfame--two compounds that are commonly used to sweeten foods [Chem. Commun., 2004, 630]. All of the salts melt below 100 ºC, and seven of them are liquids at room temperature. The team was led by associate professors of chemistry Norris W. Hoffman and James H. Davis Jr.

Room-temperature ionic liquids have been widely touted as potential designer solvents for clean technologies because they have no detectable vapor pressure, they are thermally stable and nonflammable, and they are undemanding and inexpensive to manufacture.

"The sweetener anions we use," Davis says, "are nontoxic and have advantages over other innocuous organoanions, such as acetate and lactate, that have been used to formulate ionic liquids.

"Saccharinate and acesulfamate anions are not as strongly coordinating toward metals as carboxylates," Davis explains. "They are also not as basic and do not as readily engage in hydrogen bonding."

Two of the ionic liquids prepared by the Alabama team are formed from butyryl choline, a nontoxic cation. The successful creation of ionic liquids by pairing nontoxic anions with nontoxic cations "further underscores the possibilities which exist for creating new ionic liquids that may prove to be wholly benign," the team concludes.