Static permittivities of n-propanol mixtures with ethanol, isomers of propanol, and butanol at temperature (288.15–308.15) K

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Abstract

The relative static permittivities of six binary systems of n-propanol with ethanol, i-propanol, isomeric butanols are reported as a function of composition at temperatures 288.15 K; 293.15 K; 298.15 K; 303.15 K and 308.15 K. From the experimental results, the excess relative permittivity, εrE, the permittivity temperature coefficient, (∂lnεr / ∂T), and their excess values at the 298.15 K were calculated. The excess parameters have been fitted to the Redlich–Kister polynomial equation. The results on dielectric measurements were used in the analysis of the hydrogen bond intermolecular interactions occurring between the constituents of alcohol mixture, their dependence on the number of carbon atoms, and the position of the hydroxyl group in the structure of molecules (the type of alcohols).

Highlights

► Values εr of mixtures of n-propanol with six alcohols (C1–C4) have been determined. ► Values εrE, lnεr/T and lnεr/TE at the 298.15 K have been calculated. ► The excess parameters have been fitted to the Redlich–Kister polynomial equation. ► Intermolecular interactions were analyzed.

Introduction

Dielectric studies of mixed solvents play an important role in the knowledge and understanding of intermolecular interactions in dipolar liquid mixtures. This applies to both, dipole–dipole interactions and hydrogen bonds formed in the mixture. The relative static permittivity, εr, and the calculated excess permittivity values can give information about the structural properties of polar solvents. The dependence of relative permittivity, εr, on temperature provides information about the dynamics of the microstructures [1]. Dipole moments of alcohol molecules depend on the polarity of the single bondOH group and the values for pure solvents are similar. Therefore, the changes in the dielectric permittivity as a function of the mixed solvent composition are mainly related to the intermolecular interactions. A review of the literature indicates that only a few works are devoted to the study of static dielectric of alcohol + alcohol mixtures [2], [3], [4], [5], [6], [7]. In our previous papers we have presented the results of the systematic studies of the static relative permittivity of mixtures of methanol with aliphatic alcohols containing 2 to 4 carbon atoms in the molecule [5] and mixtures of four isomeric butanols [7]. This paper presents the results of the static permittivity mixtures propan-1-ol with other alcohols containing up to 4 carbon atoms in the molecule. Thus, this paper is a direct continuation of our previous works. In addition to research the relative static permittivity, some authors have used different methods for the research of the dielectric properties of mixtures of alcohol with an alcohol, such as time domain reflectometry (TDR) [8] or dielectric relaxation spectroscopy [9], [10], [11]. It should be emphasized, that these research methods do not provide precise values of static permittivity, as shown in the work [5].

The purpose of this paper is to present the study of static permittivity of six binary mixtures of propan-1-ol (n-PrOH) with ethanol (EtOH), propan-2-ol (i-PrOH), butan-1-ol (n-BuOH), 2-methyl-propan-1-ol (i-BuOH), butan-2-ol (s-BuOH) and 2-methyl-propan-2-ol (t-BuOH) over the whole composition range at five temperatures (288.15–308.15) K.

Section snippets

Chemicals

Analytical grade reagents purchased from Merck, Fluka, and Aldrich were used. All solvents were stored in dark bottles over molecular sieves (Sigma, 0.3–0.4 nm) to reduce water content. Before use, they were double distilled and degassed in an ultrasound bath. The purity of the alcohols were tested by a comparison of the densities, d, refractive indices, nD, relative permittivity, εr, and relative temperature coefficient, (∂lnεr / ∂T), at 298.15 K with their corresponding literature values (Table 1

Results and discussion

The experimental values of relative permittivity for the investigated binary mixtures at (288.15, 293.15, 298.15, 303.15, and 308.15) K are reported in Table 2.

From the experimental data of relative permittivity, the excess values, εrE, were calculated according to the following equation:εrE=εrx1εr1+x2εr2and afterwards they were fitted to the Redlich–Kister [34], [35] equation to obtain the parameters ai:εrE=x1x2i=0naix2x1iwhere: x1, x2 — the mole fraction of components (1), (2); εr1, εr2

Conclusions

The relative static permittivity of the binary alcohol mixtures (n-propanol with ethanol, iso-propanol, n-butanol, iso-butanol, sec-butanol, and tert-butanol) at five temperatures (every 5K in the interval from 288.15 K to 308.15 K) have been measured over the entire composition range. The relations of εr, εrE, (∂lnεr / T), (∂lnεr / T)E values as the function of the composition for the mixed solvents studied here at 298.15 K have been analyzed. It has been established that the above dielectric

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