Elsevier

Thermochimica Acta

Volume 531, 10 March 2012, Pages 28-34
Thermochimica Acta

Excess molar enthalpies of ternary mixtures containing o-toluidine + tetrahydropyran with pyridine or isomeric picolines or benzene or toluene at 308.15 K

https://doi.org/10.1016/j.tca.2011.12.023Get rights and content

Abstract

Excess molar enthalpies, HijkE of o-toluidine (i) + tetrahydropyran (j) + pyridine or α- or β- or γ-picoline or benzene or toluene (k) ternary mixtures have been measured over entire mole fraction at 308.15 K using 2-drop calorimeter. The experimental data have been fitted to Redlich–Kister equation to evaluate ternary parameters along with their standard deviations. The HijkE values for the studied mixtures except those of o-toluidine (i) + tetrahydropyran (j) + toluene (k) are negative over entire composition range. The topology of the constituents of the mixtures has been utilized to (Graph theory) predict HijkE values of the investigated mixtures. The observed data have also been analyzed in terms of Prigogine–Flory–Patterson theory, It has been observed that HijkE values predicted by Graph theory compare well with their corresponding experimental values.

Highlights

► The HijkE data of ternary mixtures have been measured over entire mole fraction at 308.15 K. ► The HijkE data have been fitted to Redlich–Kister equation to evaluate adjustable ternary parameters. ► The observed data have been analyzed in terms of Graph and Prigogine–Flory–Patterson theories. ► The HijkE values predicted by Graph theory compare well with their corresponding experimental values.

Introduction

Thermodynamic studies of chemical and biological systems are of vital importance particularly from the point of view of contemporarily development of science and technology right from nano size to macromolecular levels. The present day advancement in scientific and technological fields is pouring huge quantity of new and challenging data that needs to be analyzed using thermodynamic tools to understand aspects of the observed behavior. The excess molar enthalpies, HE data of liquid mixtures are an important probe to use for the design of heat exchangers, reactors and separation units [1]. This property of liquid mixtures provides an important tool to draw information on the structure and strength of molecular interactions among constituents of mixtures. The sign, magnitude and symmetry of this property arise due to molecular interactions during the mixing process. In comparison with excess molar enthalpies data reported in the literature for the binary mixtures, the experimental data for ternary mixtures are limited. In our previous papers [2], [3], [4], [5], we reported excess molar volumes, VE, excess molar enthalpies HE and excess isentropic compressibilities, κSE data of o-toluidine or tetrahydropyran (i) + pyridine or α- or β- or γ-picoline or benzene or toluene (j) mixtures. In this communication, we report excess molar enthalpies, HijkE data for ternary mixtures of o-toluidine (i) + tetrahydropyran (j) + pyridine or α- or β- or γ-picoline or benzene or toluene (k). Further, there are no other literature data on excess molar enthalpies of the investigated mixtures.

Section snippets

Experimental

o-Toluidine (OT) (Fluka, 0.99 GC), tetrahydropyran (THP) (Fluka, 0.98 GC), pyridine (Py) (Fluka, 0.99 GC), α-picoline (Fluka, 0.98 GC), β-picoline (Fluka, 0.99 GC), γ-picoline (Fluka, 0.99 GC) benzene and toluene (AR Grade) were purified by standard methods [6]. The purity of the experimental liquids was checked by comparing their measured densities (at 308.15 ± 0.01 K) with those reported in the literature [1], [4], [5], [7], [8]. The measured densities, ρ values for the various liquids along

Results

The measured excess molar enthalpies, HikE values of ternary OT (i) + THP (j) + Py or α- or β- or γ-picoline or benzene or toluene (k) mixtures at 308.15 K (recorded in Table 2) were fitted to Redlich–Kister equationHijkE=xixkn=02Hij(n)(xixj)n+xjxkn=02Hjk(n)(xjxk)n+xkxin=02Hik(n)(xkxi)n+xixjxkn=02Hijk(n)(xjxk)nxinwhere Hij(n), etc. are adjustable parameters of various binaries of OT (i) + THP (j) + Py or α- or β- or γ-picoline or benzene or toluene (k) ternary mixtures and were taken from the

Discussion

We are unaware of any HijkE data of the investigated mixtures with which to compare our results. The HijkE data for OT (i) + THP (j) + Py or α- or β- or γ-picoline or benzene (k) mixtures are exothermic over entire composition range, while those for OT(i) + THP (j) + toluene (k) mixture, the sign of HijkE values is dictated by the relative composition of its constituents. The sign and magnitude of HijkE values are due to cumulative effects of various contributions like (i) molecular interactions in

Excess molar enthalpies of ternary mixtures

Topological investigations of VE, HE and κSE data for binary OT or THP (i) + Py or α- or β- or γ-picoline or benzene or toluene (j) mixtures [2], [3], [4], [5] have revealed that (i) OT or Py or α- or β- or γ-picoline exist as associated molecular entities; (ii) THP is characterized by dipole–dipole interactions and (iii) benzene or toluene exist as monomer. Further, VE, HE and κSE data predicted by Graph theory agree well with their experimental values which in turn lends support to assumptions

Prigogine–Flory–Patterson (PFP) theory

According to PFP theory, excess molar enthalpies for ternary mixtures are due to two contributions, (i) interactional contribution; and (ii) free volume contribution. The interactional contribution is dependent on interaction energy parameters, χij**, etc. binaries of (i + j + k) ternary mixtures. Free volume contribution arises from the dependence of the reduced volume on the reduced temperature as a result of difference between the degrees of expansion of the component. Further, pressure effect

Acknowledgement

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

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