The study of physico-chemical properties of binary systems consisting of N-Methylcyclohexylamine with 2-alkanols at T = (298.15–328.15) K

https://doi.org/10.1016/j.jct.2017.02.023Get rights and content

Highlights

  • Excess molar volume and refractive index deviations of binary systems were determined.

  • Excess molar volume and refractive index deviations were correlated by the Redlich–Kister equation.

  • The effect of temperature and chain length of alcohol were discussed.

  • Comparsion for nD was done between experimental and calculated data by equations.

Abstract

In this work, densities, ρ and refractive indices, nD of N-Methylcyclohexylamine + 2-alkanols have been measured over the entire range of composition at four temperatures 298.15, 308.15, 318.15 and 328.15 K and ambient pressure (81.5 kPa), using Anton Paar DMA 4500 oscillating densimeter and Anton Paar Abbemat 500 automatic refractometer. From experimental data, excess molar volumes, VmE, partial molar volumes, Vi, apparent molar volumes, Vϕi, thermal expansion coefficients, α, excess thermal expansion coefficients, αE, isothermal coefficients of excess molar enthalpy, (HmE/P)T,x, and refractive index deviations, ΔnD, have been calculated for binary systems consisting of N-Methylcyclohexylamine + 2-alkanols (2-propanol, 2-butanol, 2-pentanol, 2-hexanol, 2-heptanol and 2-octanol). The excess molar volumes, VmE, and refractive index deviations, ΔnD were correlated with the Redlich–Kister polynomial equation. The effect of temperature and chain length of alcohol on the excess molar volumes and refractive index deviations are discussed in terms of molecular interaction between unlike molecules. The excess molar volumes were negative and refractive index deviations were positive over the entire composition range and were plotted against the mole fraction of 2-alkanols over the entire composition range. Negative excess molar volumes and positive refractive index deviations indicate the strong hydrogen bonding between unlike molecules of mixtures. A comparative study has been made of the refractive indices obtained experimentally and those calculated by means of the Lorentz–Lorenz, Gladstone–Dale, Weiner and Arago–Biot relations.

Introduction

The thermodynamic and transport macroscopic properties of liquid mixtures are the reflection of the intermolecular forces and microscopic structure of the liquids. It is very important to know some of the physical properties like density, refractive index, viscosity or dielectric constant, to understand the interaction between different molecules in the liquid solutions. The variations of these properties with concentration give important information about intermolecular interactions and solvent structure [1], [2], [3], [4]. Moreover, knowledge of these excess molar properties can be helpful in predicting the solution behavior of solvents. Excess and deviation properties of mixtures are complex properties because they depend not only on solute-solute, solvent-solvent and solute-solvent interactions, but also of the structural effects arising from interstitial accommodation. Knowledge of several properties such as transport and electromagnetic quantities is required for engineering design and for subsequent operations. Alcohols are a class of compounds with polar character and have relatively high dielectric constants and are self-associated with hydrogen bonding. N-Methylcyclohexylamine, the common component exhibits self-association due hydrogen bonding in pure state. Further, the amine group tends to participate in hydrogen bonding interaction with 2-alkanols. Hydrogen bonding is one of the most important types of intermolecular interactions play an important role in various physicochemical, biological and industrial processes.

In the present paper, as a continuation of our research group works, we report the densities of binary liquid systems of (2-propanol, 2-butanol, 2-pentanol, 2-hexanol, 2-heptanol and 2-octanol with N-Methylcyclohexylamine) at T = (298.15–328.15) K over the entire range of concentration using a vibrating-tube densimeter. Experimental data for these systems allow us to test various equations appearing in the literature to predict their thermodynamic properties. These properties of pure liquids and their mixtures and mathematical models are very useful to design chemical processes.

Section snippets

Materials

2-Propanol was provided by Merck with a mass fraction of 0.998 and 2-butanol, 2-pentanol, 2-heptanol and 2-octanol were purchased from Merck, which purities in mass fraction were 0.99. Also 2-hexanol and N-Methylcyclohexylamine were supplied by Sigma- Aldrich with a mass fraction of 0.99. Information about the liquids employed in this work summarized in Table 1. The density and refractive index of the pure compounds were compared to literature data [5], [6], [7], [8], [9], [10], [11], [12], [13]

Densities and excess molar volumes

Excess molar volume for all mixtures was calculated from measured density at T = (298.15–328.15) K with intervals of 10 K in ambient pressure (81.5 kPa) by using the following equation:VmE=i=1NxiMi(ρ-1-ρi-1)where ρ, is the density of system, ρiandMi are the density and molar mass of the pure component and xi is the mole fraction. Excess molar volumes for binary systems of 2-propanol, 2-butanol, 2-pentanol, 2-hexanol, 2-heptanol and 2-octanol with N-Methylcyclohexylamine at T = (298.15–328.15) K were

Discussion

The density of N-Methylcyclohexylamine has been reported by C. Narasimha Rao et al. [32] and Losetty Venkatramana et al. [33] at T = 303.15 K using pycnometer. Also density of N-Methylcyclohexylamine has been reported by von H. Rupe [34] at T = 293.15 K. Fig. 1 shows the comparison of the present results for density of N-Methylcyclohexylamine with the data reported by various authors [32], [33], [34] graphically. The comparison of our density at T = 303.15 K with data reported by C. Narasimha Rao et al.

Conclusion

The density of six binary mixtures of 2-alkanols (2-propanol, 2-butanol, 2-pentanol, 2-hexanol, 2-heptanol and 2-octanol) with N-Methylcyclohexylamine were measured over the temperature range of (298.15–328.15) K and over the entire composition range. Data of the excess molar volumes for these binary mixtures were calculated from the values of the experimental density. As Fig. 2 shows, the excess molar volumes obtained are negative over the entire composition range and absolute values of VmE

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