Speeds of Sound and Excess Molar Volume for Binary Mixture of 1,4-Dioxane with 1-Heptanol at Five Temperatures

Speed of sound and density data for dilute liquid solutions of cyclic ether 1,4-dioxane with 1-heptanol was obtained using the AntonPaar DSA 5000 at five temperatures T = (298.15, 303.15, 308.15, 313.15, and 318.15) K at atmospheric pressure.The excess parameters were calculated from experimental data and fitted with a Redlich-Kister polynomial function and concluded the presence of weak molecular interactions.


Introduction
Cyclic ethers are considered some of the most important chemicals in the industry.Particularly, branched ethers (such as 2-methoxy-2-methylpropane or MTBE, 2-ethoxy-2-methyl-propane or ETBE, 2,2  -oxybis [propane] or DIPE, and 2-methoxy-2-methylbutane or TAME) have extensively been used as oxygenates in gasoline production.Cyclic ethers, in turn (e.g., 1,3-dioxolane, 1,4-dioxane, 1,3,5-trioxane, tetrahydrofuran, and tetrahydropyran), are frequently used as solvents in chemical and electrochemical processes, likewise as basic reagents (i.e., monomer) for ring-opening polymerization, and for the production of other chemical intermediaries.1-Heptanol is often utilized in cardiac electrophysiology experiments to block gap junctions and increase axial resistance between myocytes.Increasing axial resistance will decrease conduction velocity and increase the heart's condition to reentrant excitation and sustained arrhythmias.It has a pleasant smell and is employed in cosmetics for its fragrance.
Speeds of sound and deviations in isentropic compressibilities have been previously reported by the author in their earlier studies on 1,4-dioxane + 1-butanol [1] at five temperatures  = (298.15, 303.15, 308.15, 313.15 and 318.15)K.In the continuation of investigation on excess thermodynamics functions of cyclic ethers in polar and non-polar solvents, authors are reporting the experimental values, deviations in isentropic compressibility (Δ  ), excess molar volumes (   ), excess free length (   ), excess acoustic impedance (  ), and excess sound velocity (  ) for the binary system 1,4-dioxane+ 1-heptanol.The parameters are estimated using standard equations that are reported by many authors [2][3][4][5].These excess parameters are discussed in the focus of intermolecular interactions present in the mixture at  = (298.15,303.15, 308.15, 313.15, and 318.15)K using Anton-Paar.At the end for the best fit of the result Redlich-Kister coefficients and their related standard deviations are enclosed.

Experimental Procedure
In the present study the chemicals 1,4-dioxane and 1-heptanol are purchased from Sigma Aldrich chemical company, their mass fraction purities is >0.998.To begin with for the measurements purpose all prepared solutions were done at the same particular temperature, also changing the temperature the measurements were repeated.Speeds of sound, , densities, , of the pure compounds, and their mixtures were obtained with an Anton-Paar DSA-5000 vibrating tube densimeter and sound analyzer.All controls, adjustments, and checks were done using manufacturer's software installed in the device.A computer connected 2

Results and Discussion
The derived excess parameters such as Δ  ,    ,    ,   , and   at above five temperature are summarized in Tables 2(a) and 2(b).From the tables, it is observed that, the experimental speed of sound values of the binary liquid mixture decreases up to the mole fraction of 0.4090 (at 298.15, 303.15 K), 0.5244 (at 308.15, 313.15, 318.15 K) and then increase with increasing mole fraction of 1,4-dioxane, whereas the density increases with increasing mole fraction.This indicates that there is a dipole-induced dipole interaction between component molecules [3,16].The experimental data measured values of speed of sound () and density () various thermoacoustical parameters: isentropic compressibility: molar volume: where intermolecular free length: where  is Jacobson's constant, temperature dependent, specific acoustic impedance: The strength of interaction between the component molecules of binary liquid system is well reflected in the excess functions from ideality.The excess thermodynamic properties such as Δ  ,    ,    ,   , and   have been calculated using the following equation: where  1 and  2 are mole fractions of 1,4-dioxane and 1heptanol, respectively.Further, the excess parameters were fitted to Redlich-Kister polynomial equation to estimate the adjustable parameters: Using least-squares regression method, the   coefficients are obtained by fitting the above equation to the experimental values.The optimum number of coefficients are ascertained from an examination of the variation in standard deviation () equation as where  is the number of data points and  is the degree of fitting (i.e.number of coefficients) these values are reported in Table 3.
Generally, the values of the excess functions Δ  ,    , and    depend upon several physical and chemical contributions [3,17].The physical contribution depends mainly on two factors, namely,  positive, presented in Figures 1, 2, and 3.The positive values reveal that there are present weak interactions in the mixture.
Figure 4 shows that the excess acoustic impedance becomes more negative at 0.5244 mole fraction of the binary mixture.The negative values of   [1,18] indicate that the breaking of hydrogen bond in 1-heptanol leads to weak packing of the structure.Also, Figure 5 shows   values exhibiting negative deviations over the entire composition range of 1,4-dioxane in the mixture at all five temperatures studied.The negative deviations of   and   suggest that dispersion forces are operative in the system.Similar reports are made by Ali et al. [19].Further, Bahadur et al. [20] and Sumathi and Govindarajan [3].According to their reports the negative values of   indicates the decrease in the strength of interaction between the molecules in the mixture.In the present work the negative deviations of   and   suggests Advances in Chemistry the presence of weak interaction dispersive forces between the unlike molecules.

Conclusion
Speed of sound and density for binary mixture that consist of 1,4-dioxane with 1-heptanol system are measured at  = (298.15, 303.15, 308.15, 313.15, and 318.15)K using Anton-Paar.The derived acoustical parameters and their excess parameters Δ  ,    , and    are positive and   ,   are negative which hint to the presence of weak dispersive forces between the component molecules in the mixture at all five temperatures studied.
fractions of these samples were determined by measuring the mass of each component with a precision balance Sartorius, model CP 225D, ±0.01 mg.

Table 3 :
Coefficients (  ) and standard deviation () for 1,4-dioxane + 1-heptanol.The chemical contributions include breaking up of the associates present in pure liquids, resulting in positive Δ  ,    , and    .In the present mixture the graphical representations for deviation isentropic compressibilities (Δ  ), excess molar volumes (   ), and excess free length (   ) are