The present paper is part of our ongoing research on the thermodynamic properties of binary liquid mixtures [1] containing 1,4-dioxane with 1-alkanol at 303.15 K. Therefore their binary mixture properties are needed as a useful database in a variety of industrial applications [2] [3] [4] [5] [6]. Therefore, their interactions with different types of liquids such as 1,4-dioxane, methanol, ethanol, propanol, butanol, hexanol and octanol are important from a fundamental viewpoint. A wide range of important binary mixtures containing the above liquids have been studied by different authors [7] [8] [9] [10]. More over, to the best of our knowledge, no physical property data on the mixtures in the present study are available. This prompted us to undertake a study on the measurement of physical properties such as density (ρ), viscosity (η) and sound velocity (u) at 303.15 K. Using these data, the excess molar volume (VE), deviations in viscosity (Δη) and deviation in isentropic compressibility (ΔK_s) were calculated. The results are graphically presented. The excess properties values have been interpreted in terms of the nature of intermolecular interactions between constituent molecules of mixtures [11] - [19].

The chemicals (AR grade) employed were supplied by Merck. Chem. Ltd. India, Their purities (in mass percent) were 1,4-dioxane 99%, methanol 99.27%, ethanol 99.2%, propanol 99.2%, butanol 99.5%, hexanol 99.3% and octanol 99%. All the chemicals were purified by a method given in the literature [20]. The purity of the liquids was also checked by measuring their densities, viscosities and sound velocities at 303.15 K and were in agreement with the literature values [21] - [29] are depicted in Table 1.

All six binary liquid mixtures Viz. 1,4-dioxane + methanol, 1,4-dioxane + ethanol, 1,4-dioxane + propanol, 1,4-dioxane + butanol, 1,4-dioxane + hexanol and 1,4-dioxane + octanol were studied. Binary mixtures were prepared by weight covering the entire mole fraction range. The components of binary mixtures were injected by means of syringe in to the glass vials of sealed with rubber stopper in order to check evaporation losses during sample preparation. The weight of the sample was measured using electrical single pan analytical balance (K-roy instruments Pvt. Ltd. Varanasi (U.P.) India. The densities of pure liquids and their binary mixtures were measured (303.15 K) using a single-capillary pycnometer, made of borosil glass, having a bulb capacity of 30 cm³. The capillary, with graduated marks, had a uniform pore and could be closed by a well-fitted glass cap. The marks on the capillary were calibrated by using double-distilled water at 303.15 K. The pycnometer was kept for about 30 minute in an electronically controlled thermostate water bath (MSI Goyal Scientific Meerut) 303.15 ± 0.02 K and the position of the liquid level on the capillary was noted. The volume of the pycnometer at each mark was calculated by using the literature [30] value of the density of

pure water at 303.15 K. The volume these obtained is used to determine the density of the unknown liquid. The observed values of densities of pure 1,4-dioxane, methanol, ethanol, propanol, butanol, hexanol and octanol at 303.15 K were 1.0108, 0.7840, 0.7720, 0.8070, 0.8040, 0.8128 and 0.8242 g∙m⁻³ which compare well with corresponding literature values of respectively. The ultrasonic velocities were measured using a multifrequency ultrasonic interferometer (Model F-80D, Mittal Enterprise, New Delhi) working at 3 MHz. The meter was calibrated with water and benzene at 303.15 K. The measured values of ultrasonic velocities of pure 1,4-dioxane, methanol, ethanol, propanol, butanol, hexanol and octanol at 303.15 K were 1348, 1084, 1141, 1182, 1196,1298 and 1327 m ∙s⁻¹ respectively, which compare well with the corresponding literature values. The viscosity was measured by means of a suspended Ubbelohde type viscometer [31] calibrate was done at 303.15K with double distilled water and purified methanol. An electronic digital stop watch with readability of ±0.01 was used for the flow time measurements. The measured values of viscosities of pure 1,4-dioxane, methanol, ethanol, propanol, butanol, hexanol and octanol at 303.15 K were 1.0303, 0.4949, 1.1399, 1.5477, 2.2045, 4.5642 and 7.8512 C .P. which compare well with the corresponding literature values. The mixtures were prepared by mixing known volumes of the pure liquids in air tight stoppered bottles. The weights were taken on a single pan electronic balance (Mittal Enterprises New Patel Nagar, New Delhi, India) accurate to 0.01 mg.

The experimental values of density, viscosity, and sound velocity data for mixtures of 1,4-dioxane 1) and primary alcohols 2) such as methanol, ethanol, propanol, butanol, hexanol and octanol were used to calculate the excess molar volume, viscosity deviations and isentropic compressibility. The results are presented in Table 2.

The excess molar volume is calculated using the equation ( [32] [33] )

V E = ( M 1 x 1 + M 2 x 2 ) / ρ m i x .

where ρ_mix. is the density of the mixture and M₁, M₂, x₁, x₂, ρ₁ and ρ₂ are the molecular weights, mole fraction and densities of pure components 1 and 2 respectively.

Quantitatively as per the absolute reaction rate theory [34] [35] the deviation of the viscosities (Δη) from the ideal mixture values are calculated as [36]

Δ η = η m i x . − [ x 1 η 1 + x 2 η 2 ]

whereη_mix. are the viscosity of the mixture and η₁, η₂ are the viscosity of pure components (1) and (2) respectively.

Isentropic compressibility (K_S) and excess isentropic compressibility ( K S E ) are calculated from the experiment density (ρ) and sound velocity (u) using the following equations [37] [38] [39] [40] [41]

K S = 1 / u 2 ρ

Δ K S = K S − x 1 K S 1 − x 2 K S 2

where K_S, K_S1 and K_S2 are the isentropic compressibility of the mixture, pure component 1 and pure component 2 respectively.

We have calculated excess viscosity, excess molar volume and excess isentropic compressibility at 303.15 K for the binary mixture of 1,4-dioxane (1) with the primary alcohols (2). The variation of the excess properties over the entire range of compositions for the binary mixtures is depicted in Figures 1-3.

The value of excess molar volume was found to be negative value for 1,4-dioxane with methanol, ethanol and the positive value increase with increasing chain

length of the alcohols in Figure 1.

The trend it follows is CH₃OH < C₂H₅OH < C₃H₇OH < C₄H₉OH < C₅H₁₁OH < C₆H₁₃OH < C₇H₁₅OH < C₈H₁₇OH.

The negative molar volume values indicate the pressure of strong molecular interactions between the components of the mixtures. So many effects may contribute to the value of V^E, such as [42] [43] [44] (I) dipolar-interaction (II) interstitial accommodation of one component in to the other (III) possible hydrogen bond interactions between unlike molecules. The observed positive trends in (V^E) values indicate that the effect due to the breaking up of self-associated structure of the components of the mixtures is dominant over the effect of H-bonding and dipole-dipole interaction between unlike molecule. The V^E values increase in the sequence butanol < hexanol < octanol which also reflects the decreasing strength of interaction between unlike molecules in the mixture. As the size of the alkyl group increases from propanol to octanol, the steric hindrance also increases. Thus the extent of positive deviation (Figure 1) supports our view [45].

A correlation between the sign of Δη and V^E has been observed for a number of binary solvent system ( [46] [47] ) i.e. Δη is negative when VE is positive and vice-versa. In general for systems where dispersion and dipolar interactions are operating, Δη values are found to be negative, whereas charge transfer and hydrogen bonding interactions lead to the formation of complex species between unlike molecules.

The calculated ΔK_S values for the binary liquid mixture listed in Table 3. The change of this property has been shown in Figure 3. The ΔK_S values are negative over the entire mole fraction range and become more negative with increasing the mole fraction of second component for all binary mixtures. These results can be explained in term of molecular interactions and structured effects.

The variation of ΔK_S with volume fraction of 1,4-dioxane x₁ is represent in

Figure 3. Kiyohara and Benson [48] have suggested that ΔK_S is the result of several opposing effects. Strong molecular interactions occur through charge transfer, dipole-induced dipole and dipole-dipole interaction [49], interstitial accommodation and orientation ordering all lead to a more compact structure making ΔK_S negative, whereas breakup of the alkanol structure trends to make ΔK_S positive. The magnitudes of the various contributions depend mainly on the relative molecular size of the components.

Thus paper reported the densities, viscosities and sound velocity of six pure methanol, ethanol, propanol, butanol, hexanol and octanol and mixture at 303.15 K over the entire range of mole fraction. After a thorough study of the behavior of primary alcohols and 1,4-dioxane we get a clear idea about the type and amount of molecular interactions between the components. The study of excess properties along with the speed of sound has been found to very useful in understanding the nature of the interactions within binary liquid mixtures. These excess properties obtained from the correlating equations have also provided the very important and useful information.

The authors are very much thankful to the Dean Science, Head of the Department of Chemistry, Bundelkhand University, Jhansi for proving the facilities for Research work.

The authors declare no conflicts of interest regarding the publication of this paper.

Agarwal, S. and Sharma, D.K. (2021) Ultrasonic, Volumetric and Isentropic Compressibility of Binary Mixtures of 1,4-Dioxane with Primary Alcohols at 303.15 K. Open Journal of Physical Chemistry, 11, 168-181. https://doi.org/10.4236/ojpc.2021.113010