Effect of anion chain length on physicochemical properties of N,N-dimethylethanolammonium based protic ionic liquids

• N,N-dimethylethanolammonium based ionic liquids with various carboxylate anions have been synthesised.
• Density of ILs has been correlated with Gardas–Coutinho model.
• Effect of IL anion chain length on measured and derived properties has been discussed.
• Interaction energy, molecular volume and molecular radius of studied ILs were analysed.

N,N-dimethylethanolammonium (DMEA) based ionic liquids with carboxylate anions are very important in organic synthesis, gas absorption, biological and pharmaceutical applications. The fundamental physiochemical properties will give a platform to better understanding of their nature for scientific community. Here in this work, five DMEA based protic ionic liquids (PILs) with carboxylates were synthesized and their physicochemical properties such as density (ρ) and speed of sound (u) were measured as a function of temperature from (293.15–343.15) K at 0.1 MPa pressure. Several derived thermophysical properties such as molecular volume (Vm), standard entropy (S°), isothermal expansion coefficient (α) and isentropic compressibility (βs) have been calculated using experimental data. The effects of carboxylate anion chain length and temperature on physicochemical properties have been discussed. The crystal potential energy (UPOT) of ionic liquid compared with MX type of inorganic salt and discussed for ion interaction in PILs.

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