The study of molecular interactions in 1-ethyl-3-methylimidazolium trifluoromethanesulfonate + 1-pentanol from density, speed of sound and refractive index measurements

• The studied binary mixture is {[Emim][Triflate] + 1-pentanol}.
• Density, speed of sound and refractive index are measured at various temperatures.
• Derived excess/deviation parameters indicated the existence of strong interactions.
• Dominance of specific interactions explains the observed interactions.
• IR spectral studies also support the existence of strong interactions.

A molecular interaction study is carried out between the ionic liquid (IL) 1-ethyl-3-methylimidazolium trifluoromethanesulfonate and 1-pentanol using the experimental values of density, speed of sound and refractive index measurements over the whole composition range as a function of temperature between (298.15 and 328.15) K at atmospheric pressure. The excess/deviation properties, such as molar volumes (VmE), partial molar volumes (V‾mE), partial molar volumes at infinite dilution (V‾mE,∞), isentropic compressibility (κsE), free length (LfE), speeds of sound (uE), refractive index (ΔϕnD  ) and isobaric thermal expansion coefficient (αPE) obtained from the experimental values are fitted into the Redlich–Kister type equation to obtain the binary coefficients and the standard deviations. The negative values of excess properties such as VmE,κSE,LfE,αPE and the positive values of uE, ΔϕnD   clearly indicated the existence of strong molecular interactions between the studied components. The values of ∂VmE∂TP and ∂HmE∂PT are also calculated to support the existing interactions. A quantitative analysis of these parameters is further supported by IR spectroscopic analysis.