Binary Mixtures' Thermophysical Properties Study of Novel Ionic Liquids Incorporating Thiosalicylate Anion

Ionic liquids are a class of organic molten salts "designer solvents" that are composed
totally of anions (inorganic poly-atomic parts e.g., tetrafluoroborate [BF4]") and organic
cations (e.g., l-butyl-3-methylimidazolium - [BMIM]. Among the several aspects of
green chemistry, the reduction/replacement of volatile organic solvents from the reaction
medium is of utmost importance since the use of a large excess of conventional volatile
solvents required to conduct a chemical reaction creates ecological and economic
concerns. This research looks at producing a new cluster of ionic liquids which have the
same anion part of thiosalicylate [C6H4SHCOO]" with various cations of choline,
tetramethylamonium, methylimidazolium and pyridinium which the lattertwo differ on
the chain length. The chemical and physical properties such as the thermophysical
properties of density, viscosity and refractive index for the pure ionic liquids and chiefly
the density and viscosity for their binary systems with water are examined.
From experimental data the molecular volume (Fm), thermal expansion coefficient (aP),
standard entropy (S°) and crystal energy (Upot) which are considered as derived
thermophysical properties are studied for the pure ionic liquids particularly room
temperature ionic liquids (RTILs).
From the Thermal Gravimetric Analysis (TGA) the decomposition temperature for 1-
octyl-3-methylimidazolium thiosalicylate, l-butyl-3-methylimidazolium thiosalicylate,
choline thiosalicyalte, tetra-methylammonium thiosalicylate and 1-octylpyridinium
thiosalicylate as 212.02 °C, 253.2 °C, 195.34°C, 225.05 °C and 235.1 °C respectively.
Based on the experiemental data the crystal energy for l-octyl-3-methylimidazolium
thiosalicylate, 1-octylpyridinium thiosalicylate and choline thiosalicyalte were
calculated in respect to their densities at 25 °C to be 399.6 , 396.9 and 450.2 kj
correspondingly.
The dissertation included the synthesis methodology for thiosalicylate ionic liquids,
characterization of the pure ionic liquids and their binary mixtures such as densities and
viscosities, proton Nuclear Magnetic Resonance analysis (]HNMR) and the derived
thermo physical properties data for pure ionic liquids.