Thermophysical and optical studies of molecular interactions in binary mixtures of diethyl carbonate with aromatic compounds at temperatures from 298.15 to 323.15 K

• Density, speeds of sound and refractive index has been measured of DEC with aromatic hydrocarbons between 298.15 and 323.15 K.
• VmE and κsE are negative in the whole composition range may be attributed to strong ion–ion/dipole-dipole interaction.
• The effect of temperature and concentration on density, speed of sound and refractive index have been discussed.

In the present investigation, experimental densities, speeds of sound and refractive indices of binary mixtures of diethyl carbonate (DEC) with three aromatic compounds of varying nature (Aniline, Benzonitrile and Benzaldehyde) have been measured over the entire composition range at different temperatures from 298.15 K to 323.15 K employing a vibrating-tube densimeter DSA 5000M at ambient pressure 0.1 MPa. Excess molar volume, excess isentropic compressibility, excess speeds of sound and deviations in molar refraction were calculated from the density and speed of sound results. Excess properties were correlated with the Redlich–Kister polynomial equation. Values of partial excess volumes at infinite dilution for these three binary systems at different temperatures were calculated from the adjustable parameters of the Redlich–Kister smoothing equation. The excess isobaric coefficients of thermal expansion of three binary mixtures have been estimated from temperature dependence of densities. It is seen that all excess properties are negative over the entire range of composition and temperature. Strong molecular interactions are seen to exist between diethyl carbonate and aromatic compounds. The system (DEC + aniline) exhibits the maximum negative deviation from ideality among the three systems, resulting from multiple factors such as the partial interstitial accommodation effect, steric hindrance, the size of molecule and the instantaneous dipole induced dipole interactions.

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