Thermodynamic and topological investigations of ternary mixtures with o-toluidine, tetrahydropyran, and picolines: Excess molar volume and excess isentropic compressibility

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Abstract

The density, ρijk and speed of sound, uijk, ternary {o-toluidine (i) + tetrahydropyran (j) + α-, β-, or γ-picoline (k)} mixtures have been measured over the entire composition range at T = (298.15, 303.15, and 308.15) K. The excess molar volume, VijkE and excess isentropic compressibility, (κSE)ijk values of the mixtures have been predicted by using the experimental results. The observed thermodynamic properties have been fitted to Redlich–Kister equation to determine ternary adjustable parameters and standard deviations. The VijkE and (κSE)ijk values have also been analyzed in terms of (1) Graph theory and (2) Prigogine–Flory–Patterson theory (PFP). It has been observed that VijkE and (κSE)ijk data determined by Graph theory compare well with experimental values.

Highlights

► The ρijk and uijk data of ternary (OT + THP + α-, or β-, or γ-picolines) mixtures, measured at three temperatures. ► The ρijk and uijk data of the studied ternary mixtures have been employed to determine their VijkE and (κSE)ijk values. ► The VijkE and (κSE)ijk values have been fitted to Redlich–Kister equation. ► The VijkE and (κSE)ijk data has been analyzed in terms of Graph and PFP theories. ► It has been observed that Graph theory correctly predicts the sign as well as magnitude of VijkE and (κSE)ijk.

Introduction

Thermodynamic properties of liquid mixtures such as excess molar volume, excess molar enthalpy and excess isentropic compressibility contribute to obtain information about the interactions existing in liquid mixtures. Density, speed of sound and derived thermodynamic parameters from these data have been extensively employed to study molecular packing, different kinds of association and nature as well as extent of molecular interactions existing in mixtures. Further, these properties are also used to test the applicability of different models and theories, comparing their predictions with experimental data and also provide information about the nature and extent of molecular interactions existing in liquid mixtures.

Isomeric picolines are used as solvents and starting material for the synthesis of target compounds such as insecticides, herbicides, medicines, vitamins, feed additives, dyes, rubber chemicals, explosives, and disinfectants [1]. The binary or ternary liquid mixtures containing pyridines or isomeric picolines, therefore, comprise a set of liquid mixtures of great importance to chemical industries. Our project is devoted to systematic study of liquid mixtures containing pyridine or isomeric picolines. In our previous papers [2], [3], we have reported values of excess molar volume, excess molar enthalpy and excess isentropic compressibility of (o-toluidine, or tetrahydropyran + α-, β-, or γ-picoline) binary mixtures. The thermodynamic data observed have been successfully analyzed in terms of Graph theory, which involves the topology of a molecule. To our knowledge, there is no other literature data on excess molar volume and excess isentropic compressibility of {o-toluidine (i) + tetrahydropyran (j) + α-, β-, or γ-picolines (k)} ternary mixtures. In this communication, we report values of density and speed of sound of {o-toluidine (i) + tetrahydropyran (j) + α-, β-, or γ-picolines (k)} ternary mixtures. The results obtained have been utilized to determine excess molar volume and excess isentropic compressibility. An attempt has also been made to obtain expressions for excess molar volume and excess isentropic compressibility in terms of connectivity parameter of the third degree of a molecule which deals with its topology that describes well the experimental results of the mixtures investigated.

Section snippets

Experimental

With mass fraction purity reported as follows: the o-toluidine (OT) (Fluka, 0.99 GC), tetrahydropyran (THP) (Fluka, 0.98 GC), α-picoline (Fluka, 0.98 GC), β-picoline (Fluka, 0.99 GC), γ-picoline (Fluka, 0.99 GC) were purified by standard methods [4]. The provenance of the purified liquids was checked by measuring their density, recorded in table 1, using the Anton Paar DSA 5000 at T = (298.15 ± 0.01) K. The density values agreed to within ±2 · 10−3 kg · m−3 of the corresponding literature values [4], [5].

Data treatment

The results for density, ρijk, and speed of sound, uijk, data of ternary {OT (i) + THP (j) + α-, β-, or γ-picolines (k)} mixtures measured as a function of composition at T = (298.15, 303.15, and 308.15) K are recorded in table 2. Values of the excess molar volume, VijkE for the mixtures studied were predicted by employing their density values in equation (1)VijkE=i=ikxiMi(ρijk)-1-i=ikxiMi(ρi)-1,where xi, Mi, and ρi are the mole fraction, molar mass, and density of component (i), respectively. The ρ

Discussion

We are unaware of any VijkE and (κSE)ijk data of the studied ternary mixtures at T = (298.15, 303.15, and 308.15) K with which to compare our experimental results. The values of VijkE and (κSE)ijk of the mixtures investigated are negative over entire mole fraction range. The VijkE/T and (κSE)ijk/T values of the mixtures are also negative. The decrease in speed of sound values for these mixtures with increase in temperature also supports this view point. The VijkE and (κSE)ijk values of {OT (i) +

Conclusions

Values of the excess molar volume, VijkE and excess isentropic compressibility, (κSE)ijk of the mixtures investigated have been determined using their measured density and speed of sound data. An attempt has been made by considering the topology of the associated constituents of the (i + j + k) ternary mixtures to obtain expressions for predicting their VijkE and (κSE)ijk values. It has been observed that VijkE and (κSE)ijk values determined by Graph theory (which deals with the topology of a

Acknowledgments

The authors are grateful to the Head, Chemistry Department and authorities of M.D. University, Rohtak, for providing research facilities.

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