This invention describes a one pot, single-step process for the preparation of
halide-free hydrophobic salts comprising polyalkylated imidazolium cations and various anions in accordance with the following structure, where R1 and R3 represent the either the same or different
alkyl groups, and R2, R4, and R5 represent either
hydrogen atoms, or the same or different
alkyl group substituents; X represents a polyatomic anion that is the conjugate base of an acid. By simply mixing aqueous
formaldehyde with an
alkyl amine such as methylanune,
ethylamine, n-propyl oriso-
propylamine, or n-butyl-, iso-butyl, or t-
butylamine, or by mixing aqueous
formaldehyde with two alkyl amines (preferably one being
methylamine,
ethylamine, n-propyl- or iso-
propylamine, or n-butyl-, isobutyl, or t-
butylamine) and another being n-propyl- or isopropylaine, or n-butyl-, isbutyl, or t-
butylamine), an acid (such as
hexafluorophosphoric acid,
trifluoroacetic acid, pentafluoropropionic, heptafluorobutyric acid, or the
free acid of a bis(perfluoroalkylsulfonyprnide or
tris(perfluoroalkylsulfonyl)methide as the source of the anion) and aqueous
glyoxal solution, the hydrophobic ionic salts or mixtures thereof thus formed may be conveniently separated directly from the aqueous byproduct layer. Like the single cation hydrophobic salts, these mixed hydrophobic ionic liquids are non-flammable and manifest no detectable
vapor pressure up to their
decomposition temperature of greater than 300° C. We have also discovered that, surprisingly, ternary mixtures of dialkylated ionic liquids manifest higher ionic conductivities than a single
ionic liquid of the mixture alone. This property benefits electrochemical power source applications such as batteries and capacitors. Furthermore, we have discovered that ternary mixtures of dialkylated ionic liquids absorb
microwave radiation more efficiently than a single
ionic liquid of the mixture alone. This property benefits
microwave-induced synthetic reactions. Such physical and chemical properties make it possible to employ inexpensive mixtures of polyalkylated imidazolium cations in an advantageous manner as
thermal transfer fluids, high temperature lubricants, and plasticizers, and as solvents in the areas of
electrochemistry, synthetic
chemistry,
catalysis, and separations
chemistry.