Abstract :

Excess thermodynamic and transport properties of binary liquid mixtures composed of ethyl benzoate (X₁) and 2-methyl-2-propanol (X₂) were measured over the entire composition range at four temperatures: 303.15, 308.15, 313.15, and 318.15 K at atmospheric pressure. Experimental properties including excess molar volume (Vᵉ), excess isentropic compressibility (Δβₐd), viscosity deviations (Δη), excess free length (Lᵉ), excess surface tension (πᵉ), excess acoustic impedance (Zᵉ), excess enthalpy (Hᵉ), excess Gibbs free energy (Gᵉ), and ultrasonic velocity (U) were systematically evaluated. The results indicate consistently negative Vᵉ, Δβₐd, and Δη values across all compositions and temperatures, with magnitudes that reach minima near equimolar composition, suggesting strong specific interactions between unlike molecules, especially dipole–dipole and hydrogen bonding effects. Temperature rise generally reduces the magnitude of excess properties, indicative of diminished molecular interactions and structural organization at elevated thermal energy. All excess functions were correlated using the Redlich–Kister polynomial equation, demonstrating excellent fit quality and enabling estimation of binary interaction parameters. The observed trends in excess enthalpy and Gibbs free energy reveal significant non-ideal behavior, likely due to disruption of self-association in 2-methyl-2-propanol clusters upon mixing with aromatic ester molecules. Comparisons with literature reveal qualitative agreement with related binary systems involving esters and alcohols, confirming the reliability of the measured data. Overall, this study provides comprehensive thermodynamic insights into molecular interactions in ester-alcohol mixtures, supporting improved modeling of solution behavior relevant to industrial and formulation applications.

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Keywords :

Excess molar volume, Molecular interaction, Redlich–Kister correlation, Thermodynamic excess functions, Ultrasonic velocity, Viscosity deviation

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References :

1. H. Hildebrand and R. L. Scott, The Solubility of Nonelectrolytes, 3rd ed. New York, NY, USA: Reinhold, 1935.
2. N. Lewis and M. Randall, Thermodynamics and the Free Energy of Chemical Substances. New York, NY, USA: McGraw-Hill, 1923.
3. A. Guggenheim, Thermodynamics: An Advanced Treatment for Chemists and Physicists. Amsterdam, The Netherlands: North-Holland, 1957.
4. W. Gibbs, The Scientific Papers of J. Willard Gibbs, Vol. 1. New York, NY, USA: Longmans, Green and Co., 1906.
5. Redlich and A. C. Kister, “Algebraic representation of thermodynamic properties and the classification of solutions,” Ind. Eng. Chem., vol. 40, no. 2, pp. 345–348, 1948.
6. F. van Ness, “Excess functions for liquid mixtures,” J. Chem. Phys., vol. 33, pp. 987–994, 1960.
7. M. Smith, H. C. Van Ness, and M. M. Abbott, Introduction to Chemical Engineering Thermodynamics, 7th ed. New York, NY, USA: McGraw-Hill, 2005.
8. S. Rowlinson and F. L. Swinton, Liquids and Liquid Mixtures, 3rd ed. London, U.K.: Butterworths, 1982.
9. Marcus, Introduction to Liquid State Chemistry. New York, NY, USA: Wiley, 1977.
10. Marcus, “The properties of organic liquids that are relevant to their use as solvating solvents,” Chem. Rev., vol. 88, pp. 1475–1498, 1988.
11. J. Fort and W. R. Moore, “Viscosities of binary liquid mixtures,” Trans. Faraday Soc., vol. 61, pp. 2102–2111, 1965.
12. -W. Sheu and C.-H. Tu, “Excess molar volumes and viscosities of ester + alcohol binary mixtures,” J. Chem. Eng. Data, vol. 51, no. 2, pp. 496–503, 2006.
13. Djojoputro and S. Ismadji, “Density and viscosity of binary alcohol mixtures,” J. Chem. Eng. Data, vol. 50, pp. 727–731, 2005.
14. Pal and S. Kumar, “Ultrasonic and thermodynamic properties of alcohol mixtures,” J. Mol. Liq., vol. 116, pp. 47–54, 2004.
15. S. Kelkar and R. P. Phadke, “Thermodynamic properties of ester + alcohol systems,” Indian J. Chem., vol. 27A, pp. 1055–1060, 1988.
16. S. Nikam and A. B. Sawant, “Excess properties of binary liquid mixtures,” Fluid Phase Equilib., vol. 120, pp. 189–201, 1996.
17. Rajagopal and S. Chenthilnath, “Volumetric and acoustic studies of binary mixtures,” J. Pure Appl. Ultrason., vol. 23, pp. 23–29, 2001.
18. Oswal and R. Gardas, “Thermophysical properties of alcohol-based mixtures,” J. Mol. Liq., vol. 98–99, pp. 157–172, 2002.
19. Ali, A. K. Nain, and S. Chand, “Molecular interactions in ester–alcohol mixtures,” Thermochim. Acta, vol. 431, pp. 135–144, 2005.
20. Mehra and V. S. Rangra, “Ultrasonic and excess thermodynamic properties of binary liquid mixtures,” Indian J. Phys., vol. 81, pp. 485–492, 2007.
21. R. Lide, CRC Handbook of Chemistry and Physics, 84th ed. Boca Raton, FL, USA: CRC Press, 2003.
22. J. Benson, Thermodynamics and Kinetics. New York, NY, USA: Wiley, 1976.
23. Pineiro, P. Brocos, and A. Amigo, “Temperature dependence of excess properties,” Fluid Phase Equilib., vol. 190, pp. 57–71, 2001.
24. K. Rattan and M. S. Bedi, “Excess molar volumes of aromatic ester mixtures,” J. Chem. Eng. Data, vol. 45, pp. 399–403, 2000.
25. O. Hirschfelder, C. F. Curtiss, and R. B. Bird, Molecular Theory of Gases and Liquids. New York, NY, USA: Wiley, 1964.
26. Ali and S. Nain, “Acoustic and thermodynamic investigations of liquid mixtures,” Phys. Chem. Liq., vol. 48, pp. 1–15, 2010.
27. Gardas and J. C. Ahluwalia, “Thermophysical properties of binary mixtures,” J. Chem. Thermodyn., vol. 40, pp. 67–76, 2008.
28. Glasstone, Textbook of Physical Chemistry, 2nd ed. London, U.K.: Macmillan, 1961.
29. A. Barker, “Lattice theories of the liquid state,” J. Chem. Phys., vol. 20, pp. 1526–1531, 1952.
30. M. Prausnitz, R. N. Lichtenthaler, and E. Gomes de Azevedo, Molecular Thermodynamics of Fluid-Phase Equilibria, 4th ed. Hoboken, NJ, USA: Wiley, 2023.