Effects of the presence of ethylacetate or benzene on the densities and volumetric properties of mixture (styrene + N,N-dimethylformamide)

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Abstract

Densities have been measured as a function of composition for a ternary–pseudobinary mixture of {(styrene + ethyl acetate or benzene) + (N,N-dimethylformamide + ethyl acetate or benzene)} by means of a vibrating-tube densimeter at atmospheric pressure and the temperature 298.15 K. The excess molar volumes VmE were calculated from the densities and correlated using the Redlich–Kister equation to estimate the coefficients and standard errors. The experimental and calculated quantities are used to discuss the mixing behaviour of the components. The results show the third component, ethyl acetate or benzene, have a significant influence on the interaction between styrene and N,N-dimethylformamide.

Introduction

The densities and excess molar volumes of the liquids investigated and their mixtures are required, for instance, for related excess enthalpy and excess Gibbs free energy values. From a practical point of view, the data are useful for the design of mixing, storage, and processing equipment. Another aspect of studies on densities and excess molar volumes are focusing on ternary–pseudobinary mixtures, or the effects of the presence of the third component on the densities and excess volumes of the binary system [1], [2].

Liquid mixtures containing styrene and N,N-dimethylformamide (DMF) seem to be very interesting from a practical point of view due to their increased use in organic synthesis. Wang et al. [3] have reported the excess molar volume of binary mixture styrene with N,N-dimethylformamide (DMF) at T = 298.15 K. A detailed understanding about the effect of the third component on the excess thermodynamic properties and the corresponding behaviour of liquid mixtures are thus an important topic for study from both practical and fundamental researching viewpoints.

This paper is the first part of a general study of the physicochemical properties of the pseudo-binary liquid mixtures. In order to gain a wider understanding of how the presence of the third component influences the excess volumes of the binary system under research, we chose ethyl acetate or benzene as the third component. The aim is to compare the differences between ethyl acetate, the linear molecule, and benzene, a cyclic molecule, in spite of the fact that benzene is a highly toxic solvent and is not suggested for practical uses.

In this paper, we report the densities and excess molar volumes at the temperature 298.15 K and atmospheric pressure by means of a vibrating-tube densimeter over the entire range of composition for x{(1 − y)C6H5CHdouble bondCH2 + yCH3COOC2H5 or C6H6} + (1 − x){(1 − y)DMF + yCH3COOC2H5 or C6H6}, for CH3COOC2H5, y = 0.1587, 0.2544, 0.4089, 0.5052, 0.6238, 0.7529, 0.8577, and for C6H6, y = 0.1652, 0.2847, 0.3958, 0.5049, 0.6076, 0.7395, 0.8623, respectively. The results have been used to calculate the partial molar volumes and the excess partial molar volumes, and also are interpreted on the basis of possible molecular interactions between unlike molecules. The aim of this work is to provide a set of data to assess the influence of the third component, ethyl acetate or benzene, on the molecular interactions between styrene and DMF. We have not found any other reports or research results on the mixing properties of these systems at this temperature.

Section snippets

Experimental

The benzene used in these experiments was purchased from the third Shanghai Chemicals Factory, its purity greater than mole fraction 0.99. Styrene was purchased from Tianjin Chemical Factory, with the extra pure mole fraction 0.99. The ethyl acetate and DMF were purchased from Tianjing Chemicals Factory, with the extra pure mole fraction 0.99. The method of purification has been described elsewhere [4].

All the chemicals were stored in dark and brown bottles and protected against atmospheric

Results

Fourteen ternary–pseudobinary mixtures of x{(1 − y)C6H5CHdouble bondCH2 + yCH3COOC2H5 or C6H6} + (1 − x){(1 − y)DMF + yCH3COOC2H5 or C6H6} have been prepared. It is y = 0.1587, 0.2544, 0.4089, 0.5052, 0.6238, 0.7529, 0.8577 for the mixtures containing CH3COOC2H5, and y = 0.1652, 0.2847, 0.3958, 0.5049, 0.6076, 0.7395, 0.8623 for the mixtures containing C6H6. Their densities have been measured over the entire composition range at the temperature (298.15 ± 0.01) K and at atmospheric pressure 101.3 kPa, and the excess molar

Discussion

As shown in table 4 and FIGURE 1, FIGURE 2, the values of VmE are negative over the entire range of composition. That is to say, the volume of the mixing process is contracted. The fact that the polynomial coefficients A1 ≠ 0 show the changes of excess molar volume are asymmetrical about x = 0.5.

The relation of VmE(x=0.5) of mixtures with the mole fraction of ethyl acetate, or benzene, y, is shown in figure 3. From the figure, also table 4, we find for the different compositions of third

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