Excess Thermodynamic Properties of Binary Liquid System Containing (Cyclic Ether + Octan-1-Ol) At Different Temperature

ABSTRACT


INTRODUCTION
Sound velocity investigation of liquid mixtures containing of polar components are of considerable importance in understanding intermolecular interactions between the component molecules and find other industrial and technological processes [1][2][3][4][5].The study of molecular association in binary liquid mixture having alcohol as one of the component is of particular interest, since alcohols are strongly self-associated liquid having a three dimensional network of hydrogen bonds and can be associated with any other group having same degree of polar attractions.The excess molar volume (V E ), excess adiabatic compressibility (   ), excess intermolecular free length (L f E ) and excess internal pressure (Pi E ) is a good thermodynamic tool to explore the behaviour of mixtures.Alcohols and ethers represent three technically important classes of compounds.
Ethers are industrially important solvents in several chemical reactions.Alcohols are self associated organic liquids and well-known polar solvents used in a wide range of applications.The ultrasonic velocity along with density and viscosity furnish wealthy of information about the interaction between ions, dipoles, hydrogen bonding, multi-polar and dispersive forces.Ultrasonic propagation parameters yield valuable information regarding the behaviour of liquid systems because intermolecular and intramolecular association, complex formation, dipolar interactions and related structural changes affect the compressibility of the system, which in turn produces corresponding variations in ultrasonic velocity [6].
In the present study several parameters such as molar volume (V), adiabatic compressibility (  ), intermolecular free length (L f ) and internal pressure (Pi) of a binary liquid system 1,4-Dioxane + Octan-1-ol have been reported using the experimental data of density, viscosity and ultrasonic velocity of the binary liquid mixture at temperature 298.15, 303.15 and 305.15)K. From the experimental data, excess molar volume (V E ), excess adiabatic compressibility (   ), excess viscosity (  ), excess intermolecular free length (L f E ) and excess internal pressure (Pi E ) have been calculated over the entire composition range and each temperature.Excess molar volume (V E ), excess adiabatic compressibility (   ), excess viscosity (  ), excess intermolecular free length (L f E ) and excess internal pressure (Pi E ) data have been correlated using the Redlich-Kister polynomial equation.The calculated deviations and excess functions have been explained on the basis of the intermolecular interaction present in this mixture.

2.EXPERIMENTAL PROCEDURE
2.1 Chemicals.The source and purity of the chemical compound are shown in table-1.The substances density, viscosity and ultrasonic velocity is compared with the literature data (Table -2) to ascertain the purity, and a good agreement between the experimental data and literature data [12][13][14][15][16][17][18][19][20] was observed.

Apparatus and Procedure:
All two binary liquid mixtures were prepared by weighing appropriate amounts of pure liquids on a digital electronic balance (Citizen Scale (I) PVT.LTD.Mumbai, India.) with a precision ± 0.1.The experimental uncertainty in mole fractions did not exceed ± 0.0005.All the solutions were prepared by mass ratios and stored in the air-tight stopper measuring flasks.

Measurements:
Density: Densities of pure components and liquid-liquid mixtures were measured with a 25-ml specific gravity bottle by relative measurement method with an accuracy of ± 0.01 kg.m -3 .The specific gravity bottle with the experimental mixture was immersed in the temperature controlled water bath (MSI Goyal scientific, Meerut, U.P. India.),operating in the temperature range of -10 0 C to 85 0 C with an accuracy ± 0.1 0 C. Double distilled water used for the calibration of the specific gravity bottle.At least three times for each composition in experimental were generally repeated and the results were treatment.

Sound velocity:
The speed of sound (u) were measured at a frequency 3 MHz in these solutions using the interferometric method with a (Model F-80D, Mittal Enterprise, New Delhi, India) at 298.15, 303.15 and 305.15)K.The interferometer cell was filled with the test liquid, and water was circulated around the measuring cell from a water bath.The uncertainty was estimated to be ± 0.1%.The measured values of ultrasonic velocities of pure 1,4-dioxane and octan-1-ol compare well with the corresponding literature values.

Viscosity:
The viscosities of pure liquids and their binary mixtures were measured by using a Ostawald's viscometer.The viscometer was calibrated with doubly distilled water and benzene, liquid was allowed to stand for about 30 minutes in a thermostatic water bath so that the thermal fluctuations in viscometer were minimized.The accuracy in viscosity data was ± 0.0005 mPa.s.The flow time of pure liquids and liquid mixtures were repeated for five times.The efflux Time was measured with an electronic stopwatch (Racer) with a time resolution (± 0.015), and an average of at least five flow time readings was taken.Glass stopper was placed at the opening of the

Theoretical:
The experimentally measured ultrasonic velocity (u), density (ρ) and viscosity (η) are used to evaluate derived parameters like molar volume (V), adiabatic compressibility (  ), intermolecular free length (L f ) and internal pressure (Pi) using well established relations.
The molar volume (V) of binary liquid mixtures were calculated by using a following equation: The adiabatic compressibility(  ) has been calculated from the ultrasonic velocity (u) and density ()of the medium using the equation as Intermolecular free length (  ) has been determined using the standard relation as: (3) Where K ,is a temperature dependent known as Jacobson's constant.On the basis of statistical thermodynamics, Suryanarayana [33][34] derived an expression for determination of internal pressure by the use of free volume concept as: Where b stands for cubic packing factor, which is assumed to be 2 for liquids.K is a constant, independent of temperature and its value is 4.28 × 10 9 for all liquids, R is universal gas constant and T is absolute temperature.
The excess value of ultrasonic related parameters have been calculated by using the following relation Where A represents the parameter such as intermolecular free length, molar volume, isentropic compressibility, viscosity and internal pressure and  1  2 is the mole fractions of components whose parameters.

RESULT AND DISCUSSION
Assuming that ultrasonic absorption is negligible, using experimental results of the ultrasonic velocity (u), density (ρ) and viscosity () for the binary mixture Where Y E refers to excess properties and x1 and x2 are the mole fraction 1,4-Dioxane (1) and Octan-1-ol (2), and Ak represents the coefficients.Adjustable parameters of Ak were evaluated by least-squares method.The excess molar volume, inspected in project were all negative over the whole range of 1,4-dioxane at different temperatures.These are shown in figure-1.This may suggest that volume construction take place on to mixing1,4-dioxane with alcohol due to the cross-association between these various molecules [37][38].And the negative values are attributable mainly to the association between ether and alcohol intermolecular hydrogen bonds between the c-OH groups in alcohols and the oxygen atoms in the ether.The strength of the association arising from interactions between the unlike molecules was stronger than the strength of the association between the molecules.The behaviour is explained by the existence of chemical interaction (hydrogen bonding) between unlike molecules of mixture that makes the contraction of solution volume.Excess viscosity (), is found to be negative for the binary mixture over the entire composition range at all the three temperatures (Figure -3).From experimental results suggest that the negative values of () may be attributed to the formation of hydrogen bonding (O-H…….O) resulting in the formation of complexes between the component molecules and negative values suggest that the rupture f hydrogen bonded chain of the dipolar interaction between solute and alcohol exceed the intermolecular interaction through dipoledipole and hydrogen bonding between solute and alcohol.This lead to less negative values of  as temperature is raised as observed in the present binary mixture.Many workers [44][45], have reported similar behaviour where negative value of  indicates dispersive interaction.(298.15,303.15 and 305.15)K as a function of 1,4-dioxane mole fraction have been reported in table-4.Excess intermolecular free length (L f E ) is found to be negative for the binary mixture over the entire composition range at all three temperature (Figure -4), In the present paper, negative values of excess free length for 1,4-Dioxane (1) + Octan-1-ol (2) mixture can be attributed to formation of molecular complexes through dipole-dipole interaction.The negative excess intermolecular free length (L f E ) has been found to be negative for the binary mixture 1,4-Dioxane (1) + Octan-1-ol (2).Which suggest that the sound wave needs to cover a large distance.This again supports the possibility of interaction due to hydrogen bonding between unlike molecules.The internal pressure increases with increase in molar concentration indicate the association through hydrogen bonding.It show the increasing magnitude of interaction between the 1,4-Dioxane (1) and Octan-1-ol (2).The attractive forces mainly consist of hydrogen bonding, dipoledipole, and dispersion interactions.Repulsive forces, acting over very small intermolecular distances, play a minor role in the cohesion process under normal circumstances.For the binary mixture1,4-Dioxane (1) + Octan-1-ol (2), the obtained excess internal pressure (Pi E ) values are negative over the whole composition range at the studied temperatures as depicted in figure-5.The less magnitude of these values suggests that weak interactions present in the system.The excess internal pressure decreasing with the increase in mole fraction of1,4-Dioxane up to the mole fraction ( 0.6 ) and then increases with increase in mole fraction.This negative trend in (Pi E ) indicates that the only dispersion and dipolar forces operating with complete absence of specific interaction.It show the increasing magnitude of interaction between the 1,4-Dioxane (1) + Octan-1-ol (2).

CONCLUSION
In this paper the sound velocity (u), density (ρ) and viscosity () have been measure over the whole composition range at temperature T = (298.15,303.15 and 305.15)K for the binary mixture1,4-Dioxane (1) + Octan-1-ol (2).Excess molar volume, excess adiabatic compressibility, excess viscosity, excess intermolecular free length and excess internal pressure for binary mixtures have been calculated and fitted to a Redlich-Kister equation.This measured and calculated value of various thermo-acoustic parameters suggest the occurrence of complexation and through hetero molecular H-bonding between 1,4-Dioxane (1) + Octan-1-ol (2) in the binary liquid mixture.Hence it is concluded that the association in the mixture is result of hydrogen bonding between the molecule and octan-1-ol.

Excess Thermodynamic Properties of Binary Liquid System Containing (Cyclic Ether + Octan-1-Ol) At Different Temperature
The value of excess molar volume (V E ), excess adiabatic compressibility ( ), excess viscosity (  ), excess intermolecular free length (L f E ) and excess internal pressure (Pi E ) are plotted against the mole fraction of 1,4-dioxane at different temperature are shown in Figure1-5 respectively.It is observed that ultrasonic velocity (u), density (ρ) and viscosity ( ) and excess molar volume (V E ), excess adiabatic compressibility (   ), excess viscosity (  ), excess intermolecular free length (L f E ) and excess internal pressure (Pi E ) parameter shows nonlinear increasing variation with increase in molar concentration.This indicates the complex formation and intermolecular weak association may be due to hydrogen bond formation[35].This behaviour is the result of