Gutmann Acceptor Properties of LiCl, NaCl, and KCl Buffered Ambient-Temperature Chloroaluminate Ionic Liquids.

Gutmann acceptor numbers have been determined using (31)P nuclear magnetic resonance (NMR) for AlCl(3)/EMIC melts as well as LiCl, NaCl, and KCl neutral buffered melts. In AlCl(3)/EMIC melts, where EMIC is 1-ethyl-3-methylimidazolium chloride, the change in Gutmann acceptor number as a function of the AlCl(3):EMIC melt ratio is attributed to an equilibrium between a monoadduct of triethylphosphine oxide.AlCl(3) and a diadduct of triethylphosphine oxide.2AlCl(3). Observed acceptor numbers for the neutral buffered melts appear linear with respect to the melt's initial mole ratio of AlCl(3):EMIC prior to buffering. The lithium cation appears to be the most Lewis acidic alkali metal cation followed by the sodium and potassium cations. Possible reasons for the change in acceptor number as a function of changing alkali metal cation concentration are presented.