Densities, Ultrasonic Velocities, Excess Properties and IR Spectra of Binary Liquid Mixtures of Organic Esters (Ethyl Lactate, Some Organic Carbonates)

Abstract

Organic esters of carbonic acid {dimethyl carbonate (DMC)/diethyl carbonate (DEC)/propylene carbonate (PC)}, in combination with a lactate ester {ethyl lactate (EL)}, with green chemistry characteristics were chosen for the present study of molecular interactions in binary liquid mixtures. Densities (ρ) and ultrasonic velocities (U) of the pure solvents and liquid mixtures were measured experimentally over the entire composition range at temperatures (303.15, 308.15, 313.15 and 318.15) K and atmospheric pressure. The experimental data was used to calculate thermodynamic and acoustic parameters $$ V_{\text{m}}^{\text{E}} $$ , $$ \kappa_{S}^{\text{E}} $$ , $$ L_{\text{f}}^{\text{E}} $$ , $$ \bar{V}_{\text{m,1}}^{{}} $$ , $$ \bar{V}_{\text{m,2}}^{{}} $$ , $$ \bar{V}_{\text{m,1}}^{\text{E}} $$ , $$ \bar{V}_{\text{m,2}}^{\text{E}} $$ , $$ \bar{V}_{ 1}^{\text{E,0}} $$ and $$ \bar{V}_{ 2}^{\text{E,0}} $$ and the excess functions were fitted with the Redlich–Kister polynomial equation to obtain the binary solution coefficients and the standard deviations. It was observed that the values of $$ V_{\text{m}}^{\text{E}} $$ , $$ \kappa_{S}^{\text{E}} $$ and $$ L_{\text{f}}^{\text{E}} $$ are positive for the mixtures of (EL + DMC/DEC) and negative for those of (EL + PC) over the entire range of composition and temperature. The positive values of $$ V_{\text{m}}^{\text{E}} $$ , $$ \kappa_{S}^{\text{E}} $$ and $$ L_{\text{f}}^{\text{E}} $$ indicate the action of dispersion forces between the component molecules of (EL + DMC/DEC) mixtures whereas negative values for the mixture (EL + PC) suggest the existence of strong specific interactions between the component molecules, probably resulting from chemical and structural contributions. The excess properties have also been analyzed by using the reduced ( $$ Y^{\text{E}} /x_{1} x_{2} $$ ) excess function approach and the results are found to be in agreement with those from the corresponding $$ Y^{\text{E}} $$ (= $$ V_{\text{m}}^{\text{E}} $$ , $$ \kappa_{S}^{\text{E}} $$ and $$ L_{\text{f}}^{\text{E}} $$ ) values. This is further supported by FTIR spectral analysis.