Solubility of 4-methyl-2-nitroaniline in fourteen organic solvents from T = (278.15 to 313.15) K and mixing properties of solutions

doi:10.1016/j.jct.2017.02.008

The Journal of Chemical Thermodynamics

Volume 110, July 2017, Pages 33-40

https://doi.org/10.1016/j.jct.2017.02.008 Get rights and content

Highlights

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Solubilities of 4-methyl-2-nitroaniline in fourteen solvents were determined.
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Solubility data were correlated by using four thermodynamic models.
•
Mixing properties of solutions were calculated.

Abstract

The knowledge of solubility and solution thermodynamics for 4-methyl-2-nitroaniline in different solvents is essential for its preparation, purification and further theoretical studies. In this work, the solid-liquid equilibrium for 4-methyl-2-nitroaniline in fourteen organic solvents (methanol, ethanol, n-propanol, isopropanol, n-butanol, toluene, ethyl acetate, acetonitrile, 2-butanone, 1,4-dioxane, N,N-dimethylformamide, carbon tetrachloride, 1,2-dichloroethane and chlorobenzene) was built with the isothermal saturation method at temperatures T = (278.15–318.15) K under pressure of 101.2 kPa, and the solubility values of 4-methyl-2-nitroaniline in these solvents were determined by a high-performance liquid chromatography (HPLC). Generally, the mole fraction solubilities obeyed the following order from high to low in different solvents: 2-butanone > N,N-dimethylformamide > ethyl acetate > 1,4-dioxane > (acetonitrile, 1,2-dichloroethane) > chlorobenzene > (toluene, n-butanol) > n-propanol > isopropanol > ethanol > methanol > carbon tetrachloride. The obtained solubility data of 4-methyl-2-nitroaniline in the selected solvents were correlated with the modified Apelblat equation, λh equation, Wilson model and NRTL model. Results showed that the largest values of relative average deviation and root-mean-square deviation acquired with the four models were no greater than 1.03% and 6.89 × 10⁻⁴, respectively. The modified Apelblat equation provided better correlation results than the other three models. Moreover, the mixing properties, including mixing Gibbs energy, mixing enthalpy, mixing entropy, activity coefficient at infinitesimal concentration and reduced excess enthalpy were computed. The mixing process of 4-methyl-2-nitroaniline in the studied solvents was spontaneous and endothermic. The obtained solubility and thermodynamic studies would be very helpful for optimizing the preparation and purification process of 4-methyl-2-nitroaniline.

Graphical abstract

Introduction

4-Methyl-2-nitroaniline (CAS Reg. No. 89-62-3, also named as Red Base GL) plays an important role in dyeing and printing industry. It is a vital intermediate of organic pigments, azoic dyes, dispersed dyes and mordant dyes [1], [2], [3]. In addition, 4-methyl-2-nitroaniline can also be used as raw material to synthesize 3,4-diaminotoluene, which is an important synthetic intermediate for drug and pesticide [4], [5], [6], [7]. The traditional preparation method of 4-methyl-2-nitroaniline consumes a large amount of acetic acid or acetic anhydride and produces a large amount of waste acid with low yield of product [1], [8], [9], [10]. Recently, for the sake of overcoming these disadvantages, an improved process for synthesis of 4-methyl-2-nitroaniline is proposed in China, where organic solvent, such as chlorobenzene [3], dichloroethane [3], [11], [12], [13] or carbon tetrachloride [14], [15] is introduced into the reaction system. This is a very promising method for 4-methyl-2-nitroaniline production.

In order to optimize the technical conditions and speed up industrial process of this method, the knowledge of solubility and solution thermodynamics for 4-methyl-2-nitroaniline in different solvents is urgently needed. In addition, the obtained product via the traditional and improved methods is the isomeric mixtures of 4-methyl-2-nitroaniline (CAS NO. 89-62-3) and 4-methyl-3-nitroaniline (CAS NO. 119-32-4) [11], [12], [13], [14], [15], which limits their applications in lots of aspects. With the development of industry, the requirements for product purity are becoming higher and higher. Pure 4-methyl-2-nitroaniline is needed in making high purity dyes and drugs where impurities in the starting material may affect the properties of synthesized material. So the crude product must be purified before use to obtain product with high purity and yield.

As is well known, solvent crystallization is an effective technique in purification of a solid. The solubility of solid in different solvents is an important physicochemical property which plays a significant role for understanding the (solid + liquid) equilibrium (SLE) or phase equilibrium in the development of a crystallization process. In addition, knowledge of solubility values are necessary in designing the crystallization process and conducting further thermodynamic research. Solubility values are very important in the purification process of 4-methyl-2-nitroaniline via the solvent crystallization. Nevertheless, to the best of the authors’ present knowledge, no solubility data are reported in the previous works.

In order to optimize the reaction conditions for the improved production process of 4-methyl-2-nitroaniline and provide fundamental basis for separating the two isomers, the knowledge of 4-methyl-2-nitroaniline solubility in different solvents at various temperatures and the thermodynamic properties of solution is a necessary procedure. The objectives of this work are to (1) determine the solubility of 4-methyl-2-nitroaniline in solvents of methanol, ethanol, n-propanol, isopropanol, n-butanol, toluene, ethyl acetate, acetonitrile, 2-butanone, 1,4-dioxane, N,N-dimethylformamide (DMF), carbon tetrachloride, 1,2-dichloroethane and chlorobenzene at temperatures ranging from (278.15 to 313.15) K; (2) correlate the solubility data with different solubility models; and (3) calculate the mixing properties for the solution process of 4-methyl-2-nitroaniline in different solvents.

Section snippets

Thermodynamic models

In order to select a suitable model to describe the solubility behaviour for 4-methyl-2-nitroaniline in different solvents and extend the use of solubility data, in the present work, four thermodynamic models, λh equation [16], modified Apelblat equation [17], [18], [19], Wilson model [20] and NRTL model [21] are used to correlate the 4-methyl-2-nitroaniline solubility in different solvents.

Materials and apparatus

4-Methyl-2-nitroaniline with a mass fraction of 0.979 was provided by Beijing HWRK Chemical Co., Ltd, China. It was crystallized three times in ethyl acetate. The purified 4-methyl-2-nitroaniline used in solubility determination had a purity of 0.996 in mass fraction, which was confirmed by a high-performance liquid phase chromatograph (HPLC, Agilent-1260). All the solvents (methanol, ethanol, n-propanol, isopropanol, n-butanol, toluene, ethyl acetate, acetonitrile, 2-butanone, 1,4-dioxane,

Melting properties of 4-methyl-2-nitroaniline

Fig. 2 is the DSC curve of 4-methyl-2-nitroaniline. From the DSC analysis results, the melting temperature T_m and melting enthalpy Δ_fusH of 4-methyl-2-nitroaniline are 388.56 K and 21.15 kJ·mol⁻¹, respectively. The melting temperature T_m determined in this work is lower than the value reported in Ref. [27], and higher than that reported in Refs. [28], [29], but in the range presented in Ref. [26]. This case may be due to the difference in equipment, samples and/or measured conditions.

Based on the

Conclusions

The mole fraction solubility of 4-methyl-2-nitroaniline in fourteen pure organic solvents of methanol, ethanol, n-propanol, isopropanol, n-butanol, toluene, ethyl acetate, acetonitrile, 2-butanone, 1,4-dioxane, DMF, carbon tetrachloride, 1,2-dichloroethane and chlorobenzene were determined experimentally by using the isothermal saturation method at elevated temperatures under 101.2 kPa. With the increase in temperature, the mole fraction solubility of 4-methyl-2-nitroaniline in the selected

Acknowledgments

This work was supported by the Innovation Project of Jiangsu Province for Post Graduate Students (Project number: KYLX16_1396). The authors would like to express their gratitude for the Priority Academic Program Development of Jiangsu Higher Education Institutions.

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Solubility of N-hydroxy-5-norbornene-2,3-dicarboximide (HONB) in three mixed solvents of ethyl acetate + (2-methoxyethanol, methanol and 1,4-dioxane) was investigated within 278.15 K–323.15 K under 0.1 MPa. The solubility profiles indicated that the HONB solubility in measured solvents was proportional to the increment of test temperature and mass fraction of positive solvent (2-methoxyethanol, methanol or 1,4-dioxane). The mole fraction solubility of HONB varied significantly from 0.0115 in ethyl acetate + 1,4-dioxane (w₁ = 0.2066, 278.15 K) to 0.1788 in ethyl acetate + 2-methoxyethanol (w₁ = 0.7993, 323.15 K). Hansen solubility parameter was applied to reveal the miscibility and solubility order of HONB in mixed solvents, and the consequences indicated that solubility behaviors of HONB were the result of various solubility parameters comprehensive action. The measured HONB solubility employing laser monitoring technique was correlated with four activity coefficient models (Three-Suffix Margules, NRTL, UNIQUAC and Wilson) in combination with a semi-empirical model (Modified Apelblat). The smallest average values of average relative deviation (ARD) and root-mean square deviation (10⁴ RMSD) were obtained from Wilson (0.66%) and Modified Apelblat model (6.02), verifying that these two models provided more satisfactory agreement and correlation than other three models. Furthermore, the thermodynamic parameters (Δ_mixH, Δ_mixG and Δ_mixS) of the mixing process in different solvents were computed based on measured solubility values and equation parameters of Wilson model. The results demonstrated that the mixing process was entropy-driven and spontaneous. These solubility data and thermodynamic parameters could not merely extend database of HONB, but provide basic guidance for optimizing crystallization and purification process.
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Solubility of 4-methyl-2-nitroaniline in fourteen organic solvents from T = (278.15 to 313.15) K and mixing properties of solutions

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Thermodynamic models

Materials and apparatus

Melting properties of 4-methyl-2-nitroaniline

Conclusions

Acknowledgments

J. Fluorine Chem.

J. Chem. Thermodyn.

J. Chem. Thermodyn.

J. Chem. Thermodyn.

J. Chem. Thermodyn.

J. Chem. Thermodyn.

J. Chem. Thermodyn.

Fluid Phase Equilib.

J. Chem. Thermodyn.

J. Mol. Struct.

J. Chem. Thermodyn.

Synthesis and uses of o-nitro-p-toluidine

Dyestuff Ind.

Synthesis of o-nitro-p-toluidine

Fine Chem.

Cure characterization of triglycidyl epoxy/aromatic amine systems

J. Appl. Polym. Sci.

Quinoxaline-2,3-diones: potential d-amino acid oxidase (DAAO) inhibitors

Med. Chem. Res.

Improved synthesis of fast red GJ base

Hebei Chem. Eng. Ind.

Synthesis of o-nitro-p-toluidine

Dyestuff Color.

Copper-catalyzed mild nitration of protected anilines

Chem. Eur. J.

Improvement for the synthetic technology of 2-nitro-4-methylaniline

Tianjin Chem. Ind.