In this work, a series of four protic ionic liquids were synthesized by an exothermic neutralization process between N-phenyl-N-ethanolamine and stoichiometric quantity of different acids, namely, propionic acid, butyric acid, pentanoic acid and hexanoic acid. After characterization by 1H NMR and 13C NMR spectroscopic methods, density (�), speed of sound (u), viscosity (η) and conductivity (�) of neat ionic liquids have been measured 293.15 to 343.15 K and the refractive index (nD) was measured only at 303.15 K. The density and refractive index data were correlated by Gardas-Coutinho model and Lorentz-Lorenz mathematical equation, respectively, whereas viscosity and electrical conductivity were estimated by Vogel-Tammann-Fulcher (VTF) equation. Further experimental data used to calculate several derived thermodynamic properties such as thermal expansion coefficient (α), isentropic compressibility (βS), molar volume (Vm), standard entropy (S°), intermolecular free length (Lf), molar refraction (Rm) and free volume (fV). The decomposition temperature (Td) of synthesized ILs was investigated using TGA analysis. Finally, Conductor-like Screening Model for Real Solvents (COSMO-RS) computational method was also studied to understand the structural variations of the ionic liquids. © 2017 Elsevier B.V.