Study of molecular interactions in the mixtures of some primary alcohols with equimolar mixture of 1-propanol and alkylbenzoates at T = 303.15 K

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Highlights

  • Study of molecular interactions between hydrogen bonded liquid mixtures of alcohols and alkylbenzoates.

  • Liquids mixtures of some primary alcohols with equimolar mixture of 1-propanol and alkylbenzoates are considered.

  • Speed of sound, density and viscosity are experimentally determined.

  • Excess values of different thermo-acoustic parameters are calculated and discussed.

  • Experimental and theoretical results are compared for speed of sound and viscosity models.

Abstract

Speed of sound (U), density (ρ) and viscosity (η) values for the equimolar mixtures of (methyl benzoate + 1-propanol) and (ethyl benzoate + 1-propanol) with 1-butanol/1-pentanol including those of pure liquids were measured over the entire mole fraction range at T = 303.15 K. Using these experimentally determined values, various thermo-acoustic parameters such as excess isentropic compressibility (KsE), excess molar volume (VE) and excess free length (LfE), excess Gibbs free energy (ΔG∗E) and excess enthalpy (HE) have been calculated. The excess functions have been fitted to the Redlich–Kister type polynomial equation. The deviations for excess thermo-acoustic parameters have been explained on the basis of the intermolecular interactions present in these binary mixtures. The experimentally determined values of speed of sound have been used to check the applicability of different speed of sound models of Nomoto, Impedance relation, Van Dael and Vangeel, Junjie’s, free length theory and Rao’s relation. Viscosity results have been used to test the applicability of standard viscosity models of Grunberg–Nissan, Hind–Mc Laughlin, Katti–Chaudhary, Heric and Brewer, Frenkel and Tamura and Kurata at various temperatures for the binary liquid systems under study.

Introduction

The measurement of speed of sound, density and viscosity in liquids and their mixtures is useful in determining the thermodynamic and acoustical properties that are very sensitive to molecular interactions. Also such measurements are useful to study the strength of molecular interactions occurring among the component molecules besides finding extensive applications in several industrial and technological processes [1], [2]. Thermodynamic and transport properties [3], [4] of liquid mixtures provide important information with which to speculate the molecular liquid structure. These properties have been widely used to study the intermolecular interactions between various species present in the liquid mixtures. The study of thermodynamic properties of multi component liquid mixtures and data on the analysis in terms of various models are important for industrial and pharmaceutical applications [5].

Alcohol molecules are self-associated liquid molecules through inter- and intra-molecular hydrogen bonding [6]. They are of great importance for their vital role in chemistry, biology and studies on hydrogen bonding in liquid mixtures. Alcohols are widely used as solvents. On the other hand, alkyl benzoates are non-associated in solution, good hydrogen bonding acceptors. They are widely used in perfumery and pesticides. A thorough survey of literature reveals that extensive studies have been done to understand the nature of interactions occurring in different types of binary and ternary mixtures. Several researchers [7], [8], [9], [10], [11], [12] have measured the density, viscosity, and speed of sound for a wide range of liquid mixtures containing alcohols as one of the components. Even though considerable work has been reported on alcohols as one of the component in binary and ternary mixtures, the data on liquid mixtures of alcohols with alkylbenzoates is scanty.

In continuation of our earlier work on molecular interactions of liquid mixtures [13], [14], [15], [16] using excess thermodynamic and acoustic properties, the present study provides further investigation on molecular interactions in the liquid mixtures of (methyl benzoate/ethyl benzoate + 1-propanol) with 1-butanol/1-pentanol over the entire composition range. In the present study, we report the experimentally determined values of speed of sound, density and viscosity. Using these values, various thermo-acoustic parameters like excess isentropic compressibility (KsE), excess molar volume (VE), excess free length (LfE), excess Gibbs free energy (ΔG∗E) and excess enthalpy (HE) have been calculated. The results of excess values were fitted to the Redlich–Kister [17] polynomial equation. The intermolecular interactions have been estimated in the light of these excess parameters. Theoretical speed of sound and viscosity values have been evaluated using several empirical relations in the liquid mixtures considering (methyl benzoate/ethyl benzoate+1-propanol) as one component and 1-butanol/1-pentanol as the other component at T/K = 303.15. This kind of evaluation of theoretical speed of sound values proves to be useful to verify the applicability of various postulates of these theories of liquid mixtures and to arrive at some useful inferences regarding the strength of molecular interactions between component liquids in some cases.

Section snippets

Experimental

The chemicals used in the present study are, methyl benzoate, ethyl benzoate, 1-propanol, 1-butanol and 1-pentanol which are of AR grade obtained from Merck Co. Inc., Germany, with mass fraction purity greater than 0.99. All the chemicals were further purified by standard methods [18] and only middle fractions were collected. The purity analysis of the chemicals used in the present study is given in table 1 and purity was checked by gas chromatographic analysis. The density and speed of sound

Theory

The experimentally determined values of speed of sound, density and viscosity for the equimolar mixtures of {methyl benzoate (x1 = 0.4953) + 1-propanol (x2 = 0.5047)} and {ethyl benzoate (x1 = 0.4906) + 1-propanol (x2 = 0.5094)} with 1-butanol/1-pentanol at T = 303.15 K over the entire composition range are given in table 3. Using the experimentally determined values of speed of sound, density and viscosity, various thermodynamic parameters like excess isentropic compressibility (KsE), excess molar volume (VE

Results and discussion

The experimental values of the speed of sound, density and viscosity in case of the liquid mixtures under study over the entire range of composition at T = 303.15 K are given in table 3. From these available values of speed of sound, density and viscosity, the values of excess isentropic compressibility (KsE), excess molar volume (VE), excess free length (LfE), excess Gibbs free energy (ΔG∗E) and excess enthalpy (HE) were calculated. These excess parameters were plotted against mole fraction of

Conclusions

The excess parameters KsE, VE, LfE, ΔG∗E and HE were calculated from the experimentally determined speed of sound, density and viscosity values. The values of excess isentropic compressibility, excess free length and excess enthalpy are found to be negative, excess molar volume and excess Gibbs free energy of activation are positive over the entire range of composition for the liquid mixture systems considered in the present study. All these parameters indicate the presence of specific

Acknowledgements

The authors gratefully acknowledge the Project No.: ERIP/ER/0703688/M/01/1134, dated 31-03-2010 of DRDO and UGC DRS LEVEL III program No.F.530/1/DRS/2009 (SAP-I), dated 09-02-2009 New Delhi, to the department of Physics, ANU for providing financial assistance.

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