Solubility of 3,4-Dichloronitrobenzene in Methanol, Ethanol, and

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Solubility of 3,4-Dichloronitrobenzene in Methanol, Ethanol, and Liquid Mixtures (Methanol + Water, Ethanol + Water): Experimental Measurement and Thermodynamic Modeling Hongkun Zhao,*,† Hui Xu, Zhipeng Yang,† and Rongrong Li‡ †

College of Chemistry & Chemical Engineering, Yangzhou University, Yangzhou, Jiangsu 225009, P. R. China Institute of Organic Process & Chemical Engineering, TaiZhou University, Linhai, Zhejiang 317000, P. R. China

‡

ABSTRACT: The solubilities of 3,4-dichloronitrobenzene in methanol, ethanol, and liquid mixtures (methanol + water, ethanol + water) were measured in the temperature range of (278.15 to 303.15) K at 101.3 kPa by gas chromatography. The solubility of 3,4-dichloronitrobenzene in the binary mixed solvents increased with both increasing temperature and mass fraction of organic solvents. The measured solubility was correlated by the van’t Hoff equation, the modified Apelblat equation, and the λh equation. The correlated results indicated that the calculated solubility using the modified Apelblat equation had a closer agreement with the experimental data than those using the other two models. According to the measured solubility, the thermodynamic properties of dissolution of 3,4dichloronitrobenzene, including the Gibbs free energy change of solution, molar enthalpy of dissolution, and molar entropy of dissolution, were calculated by using the modified Apelblat model.

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INTRODUCTION 3,4-Dichloronitrobenzene is a very important intermediate and has various applications in many industries including industrial chemistry and medicine. For example, it can be used as a material for the synthesis of 3-chlorine-4-fluorine aniline1,2 and 2,4-dichlorofluorine benzene.3 With ongoing industrial development, increasing uses for 3,4-dichloronitrobenzene are constantly being discovered.4,5 3,4-Dichloronitrobenzene is usually prepared by the nitration of o-dichlorobenzene under appropriate reaction conditions.6,7 However, the nitration product ordinarily contains isomers of 3,4-dichloronitrobenzene and 2,3-dichloronitrobenzene. Some 3,4-dichloronitrobenzene can be separated via melt crystallization. However, this process yields a eutectic mixture of the two isomers and it is very difficult to separate a specific dichloronitrobenzene at a high purity. The purity of the 3,4-dichloronitrobenzene seriously affects the subsequent reactions. Some methods have been proposed in literature for the separation of the two isomers, including solvent crystallization,8,9 surface crystallization,10 selective adsorption on ZSM-type zeolites,11 and chemical methods.12 Among these methods, crystallization in a mixed solvent of methanol + water or ethanol + water is a very effective way to obtain a high purity of 3,4-dichloronitrobenzene. It is well-known that, during the purification process via solvent crystallization, it is necessary to determine the solubility of 3,4-dichloronitrobenzene in different solvents and the thermodynamic properties of dissolution in advance. This is necessary because these parameters are fundamental for design and optimization of the crystallization process. Obtaining the solubility data of 3,4-dichloronitrobenzene helps to determine © 2013 American Chemical Society

the crystallization process properly and improve the purity and yield of 3,4-dichloronitrobenzene. Although the solubility of 3,4-dichloronitrobenzene in mixed solvents (methanol + water, ethanol + water) is very important for the separation process, to the best of the authors’ present knowledge, no work has been reported on the dependence between temperature and the solubility of 3,4-dichloronitrobenzene. The objective of this paper was to measure the solubility of 3,4-dichloronitrobenzene in methanol, ethanol, methanol + water, and ethanol + water at a temperature range between (278.15 and 303.15) K at 101.3 kPa by gas chromatography.13,14 To obtain better solubility correlation models, the solubility data was correlated by the van’t Hoff equation, the modified Apelblat equation, and the λh equation. In addition, the solubility data was used to calculate appropriate dissolution thermodynamic properties.

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EXPERIMENTAL SECTION

Materials and Apparatus. 3,4-Dichloronitrobenzene was obtained from Zhenjiang Jingjing Chemical Co., Ltd., China. It was purified three times by recrystallization in an aqueous solution of methanol with a volume ratio of 1:1. The final purity was measured using gas chromatography (GC type Agilent 7890A Infinity GC, Agilent Technologies). Methanol and ethanol (HPLC grade) were supplied by Sinopharm Chemical Reagent Co., Ltd., China, and were used without any further purification. The water used to prepare the solutions was twice-distilled water (conductivity < 5 μS·cm−1). More Received: May 25, 2013 Accepted: October 9, 2013 Published: October 24, 2013 3061

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to 50 mL with acetone (chromatographic grade), and 2 μL of the solution was taken out and used to measure the concentration of the solute using gas chromatography (GC). The measurements were carried out using a Agilent 7890A apparatus equipped with a 30 m × 0.20 mm × 1.00 μm capillary column (model: SE-54). The detector was a flame ionization detector, and the carrier gas was nitrogen at a rate of 10 mL· min−1. The temperature of the injection chamber and detector was set to 423 K. Each analysis was carried out three times, and the average value of the three measurements was considered as the final value. The uncertainties of the measurements were estimated to be ± 0.6 %. The solubility, xe, of 3,4-dichloronitrobenzene in mole fraction in the solvent is defined as:

details about the purity of 3,4-dichloronitrobenzene and the solvents are given in Table 1. The smart thermostatic bath Table 1. Provenance and Purity of the Materials Used compound 3,4-dichloronitrobenzene methanol methanol a

provenance Zhenjiang Jingjing Chemical Co., Ltd. Sinopharm Chemical Reagent Co., Ltd. Sinopharm Chemical Reagent Co., Ltd.

m.p. /K

mass fraction purity

315.4

≥ 0.996

a

≥ 0.995 ≥ 0.997

Taken from ref 15.

(model: DC-2006) was provided by Ningbo Scientz Biotechnology Co., Ltd. and had an uncertainty of ± 0.01 K. The analytical balance (model: BSA224S) used in the experiment was provided by Sartorius Scientific Instruments (Beijing) Co., Ltd. and had an uncertainty of ± 0.0001 g. Preparation of Solvent Mixtures. All methanol + water and ethanol + water solvent mixtures were prepared by mass using a BSA224S analytical balance. The uncertainty in the mole fraction of the mixed solvents was estimated to be within ± 0.0002, in quantities of 45 g. The mass fractions of methanol and ethanol in the binary mixtures prepared varied from 0.6 to 1.0. Solubility Measurement. In this work, the gravimetric method was used to study the solubility of 3,4-dichloronitrobenzene in methanol, ethanol, methanol + water, and ethanol + water. The method for solubility measurement was similar to that described in literature.13,14 The temperature was controlled and calibrated by a smart thermostatic bath, and an analytical balance was used for weighing the solute and solution. A 50 mL Erlenmeyer flask thermostatted at T ± 0.01 K was filled with 25 g of either monosolvent or binary solvents. Excessive 3,4-dichloronitrobenzene was added to the solvent, and the solution was continuously stirred with a magnetic stirrer. A condenser was connected to the bottle and was used to prevent the solvent from evaporating. To check the equilibrium, aliquots of the liquid phase were taken at 1 h intervals through a 0.2 μm pore syringe filter, and the concentration was measured using gas chromatography (GC). When the concentration of 3,4-dichloronitrobenzene in the liquid phase became constant, it was assumed that equilibrium had been attained. The equilibrium was confirmed using two methods. The first method was taking repetitive measurements after 3 additional days, and the second was pre-equilibrating the solutions at a higher temperature and approaching equilibrium from supersaturation. It appeared that 28 h was always sufficient to reach equilibrium. Stirring was stopped 30 h before sampling to allow any solid phase to settle. Meanwhile, a 5 mL syringe was immersed in the water bath for at least 30 min to ensure that it was the same temperature as the system. After the system was at equilibrium and all solids were settled, (2 to 4) mL (accuracy: ± 0.01 mL) of upper clear liquid was taken out with the syringe attached with a filter (PTFE 0.2 μm) and transferred quickly into a 25 mL glass bottle, which was preweighed and dried by sampling. The glass bottle was quickly covered with a stopper to prevent the solvent from evaporating. The total mass was measured on an analytical balance (accuracy: ± 0.0001 g). Subsequently, the sample was diluted

xe =

m1/M1 m1/M1 + m2 /M 2 + m3 /M3

(1)

In eq 1, m1, m2, and m3 represent the masses of the 3,4dichloronitrobenzene, methanol or ethanol, and water in the mixed solvent system, respectively. Furthermore, M1, M2, and M3 are the corresponding molar masses.

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RESULTS AND DISCUSSION

Solubility Data. The measured solubility values in mole fractions of 3,4-dichloronitrobenzene in methanol, ethanol, methanol + water, and ethanol + water in a temperature range of (278.15 to 303.15) K are shown in Tables 2 and 3. T is the absolute temperature, xe is the experimental solubility, and xvan, xApelb, and xλh are the evaluated solubility data from the van’t Hoff equation, the Apelblat equation, and the λh equation, respectively. The corresponding mole fraction solubility curves are plotted in Figures 1 and 2. It can be seen from Figures 1 and 2 that the mole fraction solubility data of 3,4dichloronitrobenzene in all the selected solvents was a function of temperature and increased with increasing temperature. However, the increase of the solubility with respect to temperature was different in different solvents. At constant temperature, the mole fraction solubility values decreased when the mass fraction of methanol or ethanol in the aqueous solution was decreased. This phenomenon can be explained by the polarity of the liquid mixtures (methanol + water, ethanol + water). It was also found that the mole fraction solubility of 3,4dichloronitrobenzene was smaller in the methanol + water mixture solutions than that in ethanol + water mixture solutions when the mass fraction of methanol or ethanol was low. However, the situation was vice versa when the mass fraction of methanol or ethanol was increased in the aqueous solutions. Data Correlation. The influence of temperature and composition of the solvents on the solubility values of 3,4dichloronitrobenzene was correlated by three models, which were the van’t Hoff equation, the modified Apelblat equation, and the λh equation. The van’t Hoff model, based on thermodynamic principles, is a universal equation for (solid + liquid) phase equilibrium and is expressed as:16 3062

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Table 2. Mole Fraction Solubility (x) of 3,4-Dichloronitrobenzene in Methanol (w) + Water (1 − w) with the Temperature Range from T = (278.15 to 303.15) K at 101.3 kPaa T/K 278.15 280.65 283.15 285.65 288.15 290.65 293.15 295.65 298.15 300.65 303.15 100 RAD 104 RMSD

a

100 xe 2.083 2.512 2.956 3.532 4.223 5.048 6.111 7.243 8.732 10.47 12.47

100 xc,van 1.957 2.389 2.905 3.522 4.255 5.123 6.150 7.360 8.781 10.45 12.39

278.15 280.65 283.15 285.65 288.15 290.65 293.15 295.65 298.15 300.65 303.15 100 RAD 104 RMSD

0.6509 0.8035 0.9912 1.187 1.433 1.693 1.994 2.299 2.621 2.994 3.353

0.7394 0.8731 1.028 1.207 1.413 1.650 1.921 2.2312 2.585 2.988 3.445

278.15 280.65 283.15 285.65 288.15 290.65 293.15 295.65 298.15 300.65 303.15 100 RAD 104 RMSD

0.2222 0.2850 0.3477 0.4290 0.5145 0.6252 0.7506 0.8883 1.045 1.218 1.401

0.2473 0.2989 0.3600 0.4321 0.5171 0.6169 0.7338 0.8702 1.029 1.214 1.427

278.15 280.65 283.15 285.65 288.15 290.65 293.15 295.65 298.15 300.65 303.15 100 RAD 104 RMSD

0.07819 0.1048 0.1383 0.1766 0.2195 0.2753 0.3354 0.4065 0.4857 0.5741 0.6658

0.0966 0.1193 0.1469 0.1801 0.2201 0.2680 0.3253 0.3935 0.4745 0.5704 0.6837

100 xc,Apelb

100 RD

100 RD

w = 100 % 6.06 2.076 4.91 2.480 1.71 2.965 0.29 3.546 −0.75 4.242 −1.5 5.076 −0.64 6.076 −1.61 7.275 −0.56 8.713 0.27 10.44 0.67 12.50 1.72 7.74 w = 87.67 % −13.6 0.6479 −8.67 0.8049 −3.71 0.9873 −1.67 1.196 1.4 1.432 2.56 1.695 3.66 1.984 2.95 2.298 1.37 2.633 0.21 2.987 −2.73 3.355 3.87 5.75 w = 75.95 % −11.31 0.2233 −4.87 0.2801 −3.53 0.3478 −0.73 0.4274 −0.51 0.5203 1.32 0.6274 2.24 0.7498 2.03 0.8881 1.52 1.043 0.36 1.215 −1.87 1.404 2.76 1.55 w = 64.83 % −23.52 0.0796 −13.85 0.1052 −6.18 0.1367 −1.98 0.1751 −0.26 0.2208 2.65 0.2745 3.02 0.3366 3.2 0.4070 2.3 0.4858 0.64 0.5726 −2.69 0.6665 5.48 1.13

0.36 1.27 −0.3 −0.39 −0.45 −0.56 0.57 −0.45 0.22 0.37 −0.22 0.47 2.58

100 xc,λh 2.135 2.515 2.965 3.504 4.154 4.945 5.920 7.139 8.693 10.73 13.48

100 RD −2.51 −0.1 −0.31 0.78 1.63 2.03 3.13 1.44 0.44 −2.41 −8.04 1.48 11.48

0.45 −0.18 0.39 −0.78 0.05 −0.13 0.49 0.06 −0.45 0.25 −0.05 0.31 0.61

0.7086 0.8234 0.9593 1.122 1.317 1.556 1.852 2.226 2.711 3.360 4.268

−8.86 −2.48 3.22 5.52 8.09 8.1 7.13 3.18 −3.43 −12.22 −27.29 6.22 14.45

−0.5 1.72 −0.01 0.37 −1.13 −0.36 0.11 0.02 0.19 0.25 −0.2 0.44 0.28

0.2428 0.2874 0.3409 0.4054 0.4842 0.5815 0.7034 0.8592 1.063 1.340 1.732

−9.27 −0.84 1.97 5.49 5.88 6.99 6.29 3.28 −1.74 −9.99 −23.61 5.17 4.70

−1.78 −0.33 1.14 0.87 −0.6 0.28 −0.35 −0.13 −0.03 0.27 −0.1 0.54 0.11

0.08805 0.1081 0.1328 0.1634 0.2015 0.2497 0.3111 0.3910 0.4974 0.6436 0.8536

−12.61 −3.14 3.99 7.49 8.18 9.32 7.24 3.81 −2.41 −12.1 −28.21 7.03 2.66

Standard uncertainties for temperature and mole fraction are ± 0.01 K and 2.1 %, respectively. 3063

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Table 3. Mole Fraction Solubility (x) of 3,4-Dichloronitrobenzene in Ethanol (w) + Water (1 − w) with the Temperature Range from T = (278.15 to 303.15) K at 101.3 kPaa T/K 278.15 280.65 283.15 285.65 288.15 290.65 293.15 295.65 298.15 300.65 303.15 100 RAD 104 RMSD

a

100 xe 2.003 2.712 3.525 4.436 5.487 6.614 7.692 8.881 9.967 11.05 11.92

100 xc,van 2.806 3.303 3.877 4.539 5.298 6.168 7.163 8.297 9.587 11.05 12.71

278.15 280.65 283.15 285.65 288.15 290.65 293.15 295.65 298.15 300.65 303.15 100 RAD 104 RMSD

0.6812 0.8438 1.001 1.184 1.394 1.587 1.795 2.004 2.194 2.378 2.557

0.8126 0.9244 1.049 1.188 1.343 1.514 1.704 1.913 2.145 2.399 2.679

278.15 280.65 283.15 285.65 288.15 290.65 293.15 295.65 298.15 300.65 303.15 100 RAD 104 RMSD

0.2747 0.3368 0.4172 0.5080 0.6049 0.7051 0.8233 0.9414 1.056 1.186 1.309

0.3224 0.3765 0.4385 0.5094 0.5902 0.682 0.7862 0.9042 1.037 1.188 1.356

278.15 280.65 283.15 285.65 288.15 290.65 293.15 295.65 298.15 300.65 303.15 100 RAD 104 RMSD

0.1055 0.1335 0.1721 0.2118 0.2531 0.3020 0.3466 0.3984 0.4423 0.4871 0.5230

0.1364 0.1587 0.1842 0.2133 0.2463 0.2837 0.3260 0.3737 0.4274 0.4878 0.5555

100 xc,Apelb

100 RD

w = 100 % −40.08 −21.79 −9.99 −2.31 3.44 6.74 6.88 6.58 3.82 0.02 −6.62 9.84 50.01 w = 87.69 % −19.29 −9.55 −4.81 −0.34 3.69 4.61 5.09 4.53 2.25 −0.89 −4.78 5.44 7.89 w = 75.98 % −17.36 −11.79 −5.11 −0.27 2.44 3.27 4.5 3.95 1.76 −0.13 −3.62 4.93 3.08 w = 64.86 % −29.29 −18.9 −7.06 −0.7 2.69 6.06 5.95 6.2 3.36 −0.15 −6.21 7.87 2.01

2.041 2.713 3.513 4.435 5.463 6.572 7.728 8.887 10.00 11.03 11.92

100 RD

100 xc,λh

100 RD

−1.91 −0.05 0.34 0.02 0.43 0.63 −0.46 −0.06 −0.36 0.22 0.03 0.41 2.53

2.323 2.781 3.330 3.993 4.797 5.781 6.997 8.520 10.46 12.98 16.36

−15.98 −2.53 5.54 10 12.58 12.59 9.03 4.06 −4.94 −17.47 −37.27 9.47 78.06

0.6848 0.8369 1.006 1.190 1.385 1.588 1.795 2.000 2.198 2.384 2.552

−0.52 0.82 −0.49 −0.47 0.65 −0.08 0.0046 0.2 −0.18 −0.24 0.18 0.35 0.51

0.7519 0.8472 0.9580 1.089 1.244 1.432 1.662 1.951 2.323 2.819 3.512

−10.38 −0.4 4.28 8.04 10.74 9.77 7.39 2.63 −5.89 −18.56 −37.34 7.81 17.15

0.2734 0.3407 0.4181 0.5054 0.6023 0.7079 0.8208 0.9394 1.062 1.185 1.308

0.47 −1.16 −0.21 0.51 0.43 −0.39 0.31 0.21 −0.54 0.06 0.1 0.40 0.27

0.301 0.3474 0.4022 0.4673 0.5458 0.6416 0.7603 0.9106 1.106 1.369 1.740

−9.58 −3.15 3.61 8.00 9.77 9.01 7.65 3.27 −4.73 −15.42 −32.9 7.42 7.15

0.1050 0.1354 0.1708 0.2106 0.2543 0.3009 0.3489 0.3969 0.4431 0.4859 0.5236

0.5 −1.43 0.78 0.55 −0.49 0.37 −0.67 0.38 −0.19 0.25 −0.11 0.52 0.13

0.1188 0.1384 0.1618 0.1897 0.2235 0.2650 0.3167 0.3824 0.4683 0.5844 0.7492

−12.59 −3.69 6.01 10.44 11.69 12.26 8.63 4.01 −5.88 −19.99 −43.25 9.52 3.79

Standard uncertainties for temperature and mole fraction are ± 0.01 K and 2.1 %, respectively. 3064

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In eq 2, ΔHi, Ttp,i, ΔCp,i,Ptp,i, and γi represent molar fusion enthalpy, triple-point temperature, difference of heat capacities between subcooled liquid and solid, triple point pressure, and the activity coefficient for component i, respectively. Moreover, xi is the mole fraction solubility of component i at temperature T and pressure p, and R is the universal gas constant. Generally, the triple-point temperature was substituted with the normal melting temperature, and the last two terms on the right-hand side of the equation were canceled out. Moreover, the pressure correction was considered to be negligible. The contribution of heat-capacity difference was often small, and there was no solidto-solid conversion ranging from T to Ttp. Therefore, eq 2 was simplified to eq 3: Figure 1. Mole fraction solubility (x) of 3,4-dichloronitrobenzene in methanol and aqueous solutions of methanol at different temperatures. ■, methanol; ●, 87.67 % methanol; ▲, 75.95 % methanol; ▼, 64.83 % methanol; solid line, calculated by eq 8.

ln(xiγi) =

ΔHi ⎡ 1 1 ⎤⎥ ⎢ − R ⎢⎣ (Ttp, i /K) (T /K) ⎥⎦

(3)

The solution was ideal (γi = 1); therefore eq 4 was obtained: A +B T /K

ln xi =

(4) 16

This expression is the famous van’t Hoff equation, where A and B are the model parameters. The dependence of the measured mole fraction solubility on temperature was correlated using the van’t Hoff equation with a nonlinear least-squares regression method. The calculated solubility with relative deviations (RD), the average absolute deviation (RAD), and the root-mean-square deviations (RMSD) of 3,4dichloronitrobenzene at different temperatures in the selected solvents using the van’t Hoff equation are listed in Tables 2 and 3, respectively. The regressed values of parameters A and B are presented in Table 4. The relative deviations (RD) and the relative average deviation (RAD) between the experimental values and the calculated values are defined as follows:

Figure 2. Mole fraction solubility (x) of 3,4-dichloronitrobenzene in ethanol and aqueous solutions of ethanol at different temperatures. ■, ethanol; ●, 87.67 % ethanol; ▲, 75.95 % ethanol; ▼, 64.83 % ethanol; solid line, calculated by eq 8.

RD =

ΔHi ⎡ 1 1 ⎤⎥ ⎢ ln(xiγi) = − R ⎢⎣ (Ttp, i /K) (T /K) ⎥⎦

(5)

N

RAD =

⎤ ΔCp , i ⎡ (Ttp, i /K) (Ttp, i /K) ⎢ln − − + 1⎥ ⎥⎦ R ⎢⎣ (T /K) (T /K) −

xe − xc xe xe − xc 1 ∑ i e i N i=1 xi

(6)

Furthermore, the root-mean-square deviation (RMSD) is defined as:

ΔV (p − ptp, i ) R(T /K)

N

RMSD =

(2)

∑i = 1 (xic − xie)2 N

(7)

Table 4. Values of Parameters Obtained Using the van’t Hoff Equation, the Modified Apelblat Equation, and the λh Equation van’t Hoff equation w

A

B/K

100 % 87.67 % 75.96 % 64.83 %

18.45 13.75 15.25 16.79

−6224.92 −5189.77 −5911.77 −6601.12

100 % 87.69 % 75.98 % 64.86 %

14.74 9.65 11.69 10.43

−5094.70 −4024.01 −4846.13 −4736.39

λh equation

modified Apelblat equation A

B/K

Methanol + Water −285.69 7152.73 766.55 −38250.58 552.50 −29535.71 955.79 −47943.64 Ethanol + Water 1815.09 −84163.89 1130.33 −53141.02 987.29 −47667.01 1562.99 −72877.16 3065

C

100λ

h

45.50 −112.66 −80.39 −140.46

11.57 2.68 1.34 0.9524

37473.73 13713.02 329625.76 610460.18

−269.43 −167.77 −146.02 −232.38

17.64 1.23 0.9467 0.4656

28442.27 184777.92 353154.56 805444.69

dx.doi.org/10.1021/je400507u | J. Chem. Eng. Data 2013, 58, 3061−3068

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In eqs 5, 6, and 7, xe and xc stand for the experimental and the calculated mole fraction solubilities, respectively. The number of experimental solubility points is represented by N. Tables 2 and 3 show that the experimental solubility data of 3,4-dichloronitrobenzene in methanol, ethanol, and mixture solvents (methanol + water, ethanol + water) at a temperature range from (278.15 to 303.15) K under 101.3 kPa did not correlate with the calculated solubility data. The maximum value of relative deviations was −23.52 % for methanol + water and −40.08 % for ethanol + water. The modified Apelblat equation, which was previously used by Apelblat to determine the relationship between mole fraction solubility and temperature, is a semiempirical equation17−19 and is defined as follows: B ln x = A + + C ln(T /K ) T /K

Thermodynamic Properties for the Solution. From an energetic point of view, the dissolution of a 3,4-dichloronitrobenzene into solvent is related to changes of thermodynamic parameters. For example, molar enthalpy (ΔsolH0), molar entropy (ΔsolS0), and the Gibbs free energy (ΔsolG0) change in solution, which can be evaluated using the experimental mole fraction solubility. This change reflected the presence of the 3,4-dichloronitrobenzene at its infinite dilution state at a certain temperature.22,23 We assumed the activity coefficient of water at normal temperature is equal to 1. From the Gibbs−Helmholtz equation, eq 10 can be deduced.24 ⎛ d ln x ⎞ Δsol H 0 = R(T /K)2 ⎜ ⎟ ⎝ d(T /K) ⎠ p

The molar dissolution enthalpy (ΔsolH ) is the difference of the partial molar enthalpy (HDNB *,liquid) of 3,4-dichloronitrobenzene in solvent and the molar enthalpy of 3, 4-dichloronitrobenzene in the solid state (H0,solid DNB ) at a given temperature T, as shown in eq 11.

(8)

In eq 8, A, B, and C are parameters, T is the absolute temperature in Kelvin, and x is the mole fraction solubility of 3,4-dichloronitrobenzene in methanol, ethanol, and aqueous solutions of methanol or ethanol at temperature T. The regressed parameters A, B, and C are listed in Table 4. The calculated mole fraction solubility of 3,4-dichloronitrobenzene in methanol, ethanol, and aqueous solutions of methanol or ethanol are presented in Tables 2 and 3. It can be seen in Tables 2 and 3 that the maximum value of relative deviations is −1.78 % for methanol + water and −1.91 % for ethanol + water. Compared with the van’t Hoff model, the Apelblat model’s correlation values were closer to the experimental values. The λh equation is widely used in literature20,21 and is a semiempirical equation. Only two parameters (λ and h) were employed to correlate the experimental solubility data. In this work, the λh equation was used to fit the mole fraction solubility data of 3,4-dichloronitrobenzene in methanol, ethanol, and mixture solvents (methanol + water, ethanol + water). ⎛ 1 ⎡⎛ λ(1 − x c) ⎞⎤ 1 ⎞ ln⎢⎜1 + − ⎟⎥ = λ h ⎜ ⎟ c ⎠⎦ x Tm/K ⎠ ⎣⎝ ⎝ T /K

(10) 0

0,solid *,liquid Δsol H 0 = HDNB − HDNB

(11)

The molar entropy (ΔsolS0) and the Gibbs free energy change of solution (ΔsolG0) can be calculated using eqs 12 and 13. ⎛ d ln x ⎞ Δsol S 0 = R ⎜ ⎟ ⎝ d ln(T /K) ⎠ p

(12)

Δsol G 0 = −RT ln(x)p

(13)

Tables 5 and 6 show the calculated values of the thermodynamic parameters, ΔsolH0, ΔsolG0, and ΔsolS0 of 3,4dichloronitrobenzene in various concentrations of methanol + water and ethanol + water aqueous solutions, respectively. Tables 5 and 6 indicate that the molar enthalpy (ΔsolH0), molar entropy (ΔsolS0), and the Gibbs free energy (ΔsolG0) change of solution is positive for all cases. This phenomenon indicates that the whole dissolution process of 3,4-dichloronitrobenzene in methanol, ethanol, and aqueous solutions (methanol + water, ethanol + water) are endothermic. The highest value of the molar enthalpy in methanol + water mixed solvent occurred with a mass fraction of methanol of 64.83 %. This suggests that the dissolution process requires more energy for overcoming the cohesive force of 3,4-dichloronitrobenzene and the solvent. The standard Gibbs free energy change of solution (ΔsolG0) was also positive for all cases. However, it cannot illustrate that the dissolution process is nonspontaneous. It must be noted that the real criterion of spontaneity is the transient Gibbs energy change of solution, according to: ΔsolG = ΔsolG0 + RT ln(x)p, which can be negative, zero, or positive, according to the solute concentration in the solution. In addition, the molar entropy of solution was positive, which indicates that entropy was the driving force for the solution process. The relationship between the dissolution enthalpy of 3,4dichloronitrobenzene in the selected solvent and temperature is presented in Figure 3. It can be seen in Figure 3 that the dissolution enthalpy of 3,4-dichloronitrobenzene has a linear relationship with temperature for all of the studied solutions. As a result, the heat capacity of solution was constant during the dissolution process of 3,4-dichloronitrobenzene in each solution. Figure 3 also illustrates that the dissolution enthalpies

(9)

In eq 9, Tm is the melting temperature of 3,4-dichloronitrobenzene at normal pressure, and λ and h are two parameters. The regressed values of the two adjustable parameters are given in Table 4. The calculated mole fraction solubility of 3,4dichloronitrobenzene in methanol or ethanol and aqueous solutions of methanol or ethanol together with the corresponding root-mean-square deviations (RMSD) and the relative average deviation (RAD) are also given in Tables 2 and 3. The maximum value of relative deviations was −28.21 % for methanol + water and −43.25 % for ethanol + water. The correlation results by the λh model differed more from the experimental values than those by the Apelblat equation. In general, the modified Apelblat equation is the proper model for fitting the mole fraction solubility data of 3,4dichloronitrobenzene in methanol or ethanol and aqueous solutions of methanol or ethanol. Conclusions were drawn after analyzing the solubility data and parameters that were fitted by the van’t Hoff equation, modified Apelblat equation, and the λh equation. The modified Apelblat equation was more precise than the λh equation and the van’t Hoff equation for these investigated systems. 3066

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Table 5. Thermodynamic Properties of the Dissolution of 3,4-Dichloronitrobenzene in Methanol and Methanol + Water Solvents at Various Temperatures T K

ΔsolH0 −1

kJ·mol

278.15 280.65 283.15 285.65 288.15 290.65 293.15 295.65 298.15 300.65 303.15

45.8 46.7 47.7 48.6 49.5 50.5 51.4 52.4 53.3 54.3 55.2

278.15 280.65 283.15 285.65 288.15 290.65 293.15 295.65 298.15 300.65 303.15

57.5 55.1 52.8 50.5 48.1 45.8 43.4 41.1 38.7 36.4 34.1

278.15 280.65 283.15 285.65 288.15 290.65 293.15 295.65 298.15 300.65 303.15

59.7 58.0 56.3 54.7 53.0 51.3 49.6 48.0 46.3 44.6 43.0

278.15 280.65 283.15 285.65 288.15 290.65 293.15 295.65 298.15 300.65 303.15

73.8 70.9 67.9 65.0 62.1 59.2 56.3 53.3 50.4 47.5 44.6

ΔsolG0 −1

kJ·mol

Table 6. Thermodynamic Properties of the Dissolution of 3,4-Dichloronitrobenzene in Ethanol and Ethanol + Water Solvents at Various Temperatures

ΔsolS0 −1

T −1

J·mol ·K

w = 100 % 8.95 132.3 8.6 135.8 8.29 139.0 7.94 142.3 7.58 145.6 7.22 148.9 6.81 152.2 6.45 155.3 6.04 158.6 5.64 161.8 5.25 164.8 w = 87.65 % 11.64 164.8 11.26 156.4 10.86 148.1 10.53 139.8 10.17 131.7 9.86 123.6 9.54 115.6 9.27 107.6 9.03 99.7 8.77 91.9 8.56 84.1 w = 75.95 % 14.12 163.8 13.71 157.8 13.33 151.8 12.96 146.0 12.60 140.2 12.25 134.4 11.93 128.7 11.61 123.0 11.31 117.4 11.02 111.8 10.75 106.2 w = 64.83 % 16.50 205.9 16.00 195.5 15.53 185.1 15.08 174.8 14.65 164.7 14.25 154.6 13.88 144.6 13.53 134.6 13.20 124.8 12.90 115.1 12.63 105.4

%ζH

%ζTS

K

ΔsolH0 −1

kJ·mol

55.42 55.07 54.76 54.45 54.14 53.85 53.55 53.28 53.00 52.74 52.49

44.58 44.93 45.24 45.55 45.86 46.15 46.45 46.72 47.00 47.26 47.51

278.15 280.65 283.15 285.65 288.15 290.65 293.15 295.65 298.15 300.65 303.15

76.7 71.1 65.5 59.9 54.3 48.7 43.1 37.5 31.9 26.3 20.7

55.63 55.68 55.73 55.82 55.91 56.03 56.17 56.36 56.59 56.85 57.18

44.37 44.32 44.27 44.18 44.09 43.97 43.83 43.64 43.41 43.15 42.82

278.15 280.65 283.15 285.65 288.15 290.65 293.15 295.65 298.15 300.65 303.15

53.8 50.3 46.9 43.4 39.9 36.4 32.9 29.4 25.9 22.4 19.0

56.71 56.07 56.71 56.72 56.75 56.78 56.83 56.88 56.96 57.05 57.15

43.29 43.30 43.29 43.28 43.25 43.22 43.17 43.12 43.04 42.95 42.85

278.15 280.65 283.15 285.65 288.15 290.65 293.15 295.65 298.15 300.65 303.15

58.6 55.6 52.6 49.5 46.5 43.5 40.4 37.4 34.3 31.3 28.3

56.30 56.36 56.45 56.56 56.69 56.85 57.04 57.26 57.53 57.86 58.25

43.70 43.64 43.55 43.44 43.31 43.15 42.96 42.74 42.47 42.14 41.75

278.15 280.65 283.15 285.65 288.15 290.65 293.15 295.65 298.15 300.65 303.15

68.5 63.7 58.9 54.0 49.2 44.4 39.5 34.7 29.9 25.1 20.2

%ξH =

of 3,4-dichloronitrobenzene decrease with increasing temperature in selected solvents, except in the case of pure methanol. Equations 13 and 14, described in the literature,21,25 were used to compare the relative contribution to the Gibbs free energy change of solution by dissolution enthalpy and dissolution entropy in dissolution process:

%ξTS =

ΔsolG0 −1

kJ·mol

ΔsolS0 J·mol−1·K−1

w = 100 % 9 243.3 8.42 223.2 7.88 203.4 7.40 183.7 6.96 164.2 6.58 144.8 6.24 125.6 5.95 106.6 5.71 87.8 5.51 69.0 5.36 50.5 w = 87.65 % 11.53 152.1 11.16 139.6 10.83 127.2 10.52 115.0 10.25 102.8 10.01 90.8 9.80 78.8 9.62 67.0 9.46 55.2 9.34 43.6 9.25 32.0 w = 75.95 % 13.65 161.7 13.26 150.8 12.89 140.1 12.56 129.4 12.25 118.8 11.96 108.3 11.71 97.9 11.47 87.6 11.27 77.4 11.09 67.3 10.93 57.2 w = 64.83 % 15.85 189.4 15.44 171.9 14.98 155.0 14.62 138.0 14.32 121.0 14.02 104.4 13.81 87.8 13.58 71.5 13.44 55.2 13.31 39.1 13.24 23.0

o |ΔHsol | o o · 100 |ΔHsol| + |T ΔSsol | o |T ΔSsol | o o · 100 |ΔHsol| + |T ΔSsol |

%ζH

%ζTS

53.12 53.15 53.2 53.29 53.43 53.62 53.91 54.31 54.92 55.86 57.45

46.88 46.85 46.8 46.71 46.57 46.38 46.09 45.69 45.08 44.14 42.55

55.99 56.23 56.53 56.9 57.37 57.97 58.75 59.77 61.16 63.14 66.12

44.01 43.77 43.47 43.1 42.63 42.03 41.25 40.23 38.84 36.86 33.88

56.59 56.77 56.99 57.26 57.59 57.98 58.47 59.06 59.81 60.76 61.98

43.41 43.23 43.01 42.74 42.41 42.02 41.53 40.94 40.19 39.24 38.02

56.54 56.90 57.29 57.82 58.52 59.38 60.58 62.16 64.50 68.09 74.34

43.46 43.10 42.71 42.18 41.48 40.62 39.42 37.84 35.50 31.91 25.66

(14)

(15)

The values of % ζH and % ζTS are also listed in Tables 5 and 6. Tables 5 and 6 show the main contributor to the Gibbs free 3067

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(4) Nishino, S.; Shima, H.; Oda, H.; Suzuki, S. Production Method of 3-Halogeno-4-hydrocarbyloxy-nitrobenzene Compound. JP Patent 2,009,215,259, September 24, 2009. (5) Liu, Y. L.; Zhang, X. H.; Ma, Y.; Ma, C. An Efficient C−C bond Formation Reaction for the Synthesis of α-Arylated Ketones under Mild Conditions. Tetrahedron Lett. 2013, 54, 402−405. (6) Li, G. R.; Yu, R. G.; Xu, X. L. Preparation Method of 3,4Dichloronitrobenzene. CN Patent 102,617,353, August 1, 2012. (7) Zhang, J. Y.; Wang, W. Preparation Method of 3,4Dichloronitrobenzene by Solid Acid Catalyst. CN Patent 102,675,120, September 19, 2012. (8) Mita, R.; Umemoto, M.; Nakao, S. Purification of 3,4Dichloronitrobenzene. JPH Patent 03,190,847, August 20, 1991. (9) Cheng, X. L.; Hou, H. B. Research for Purification Process of 3,4Dichloronitrobenzene. Shenyang Chem. Ind. 1997, 26, 25−26. (10) Gordon, M. T.; Monet, G. P. Surface Crystallization Process. US Patent 3,272,875, September 13, 1966. (11) Otomo, K.; Yamaguchi, M.; Ito, M.; Tokunaga, H. Method for Separating Dichloronitrobenzene Isomers. JPS Patent 632,956, January 7, 1988. (12) Pieter, T. H.; Herne, B. Separation of Dichloronitrobenzenes and Benzonitrile Production, US Patent 3,144,476, August 11, 1964. (13) Karásek, P.; Planeta, J.; Roth, M. Solubilities of Oxygenated Aromatic Solids in Pressurized Hot Water. J. Chem. Eng. Data 2009, 54, 1457−1461. (14) Karásek, P.; Planeta, J.; Roth, M. Solubilities of Triptycene, 9Phenylanthracene, 9,10-Dimethylanthracene, and 2-Methylanthracene in Pressurized Hot Water at Temperatures from 313 K to the Melting Point. J. Chem. Eng. Data 2008, 5, 160−164. (15) PhysProp data were obtained from Syracuse Research Corporation of Syracuse, New York. (16) Stanley, M. W. Phase Equilibria in Chemical Engineering; Butterworth: London, 1985. (17) You, Y. J.; Gao, T.; Qiu, F. L.; Wang, Y.; Chen, X. Y.; Jia, W. P.; Li, R. R. Solubility Measurement and Modeling for 2-Benzoyl-3chlorobenzoic Acid and 1-Chloroanthraquinone in Organic Solvents. J. Chem. Eng. Data 2013, 58, 1845−1852. (18) Li, Q. S.; Lu, F. H.; Tian, Y. M.; Feng, S. J.; Shen, Y.; Wang, B. H. Solubility of Veratric Acid in Eight Monosolvents and Ethanol + 1Butanol at Various Temperatures. J. Chem. Eng. Data 2013, 58, 1020− 1028. (19) Zhao, H. K.; Ji, H. Z.; Meng, X. C.; Li, R. R. Solubility of 3Chlorophthalic Anhydride and 4-Chlorophthalic Anhydride in Organic Solvents and Solubility of 3-Chlorophthalic Acid and 4-Chlorophthalic Acid in Water from (283.15 to 333.15) K. J. Chem. Eng. Data 2009, 54, 1135−1137. (20) Buchowski, H.; Ksiazczak, A.; Pietrzyk, S. Solvent Activity along a Saturation Line and Solubility of Hydrogen-bonding Solids. J. Phys. Chem. 1980, 84, 975−979. (21) Wang, K.; Hu, Y. H.; Yang, W.; Guo, S.; Shi, Y. Measurement and Correlation of the Solubility of 2,3,4,5-Tetrabromothiophene in Different Solvents. J. Chem. Thermodyn. 2012, 55, 50−55. (22) Adel, N. J.; Chokri, M.; Arbi, A. Solubility of Gallic Acid in Liquid Mixtures of (Ethanol + Water) from (293.15 to 318.15) K. J. Chem. Thermodyn. 2012, 55, 75−78. (23) Zielenkiewicz, W.; Perlovich, G. L.; Wszelaka-Rylik, M. The Vapour Pressure and the Enthalpy of Sublimation: Determination by Inert Gas Flow Method. J. Therm. Anal. Calorim. 1999, 57, 225−234. (24) Adkins, C. J. Equilibrium Thermodynamics; McGraw Hill: New York, 1968. (25) Delgado, D. R.; Holguin, A. R.; Almanza, O. A.; Martinez, F.; Marcus, Y. Solubility and Preferential Solvation of Meloxicam in Ethanol + Water Mixtures. Fluid Phase Equilib. 2011, 305, 88−95.

Figure 3. Enthalpy of dissolution of 3,4-dichloronitrobenzene in methanol, ethanol, and mixed solvents (methanol + water, ethanol + water) at different temperatures. ■, wm = 1; ●, wm = 0.8767; ▲, wm = 0.7595; ▼, wm = 0.6843; ◀, we = 1; ▶, we = 0.8767; ◆, we = 0.7595; ★, we = 0.6843. The wm is the mass fraction of methanol; we is the mass fraction of ethanol.

energy change of solution was the dissolution enthalpy during the dissolution of 3,4-dichloronitrobenzene in the selected solvents, because the values of % ζH were greater than 52 %.

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CONCLUSION In this study, the equilibrium mole fraction solubility of 3,4dichloronitrobenzene in methanol, ethanol, methanol + water mixture, and ethanol + water mixture were measured at temperatures from (278.15 to 303.15) K using gas chromatography at 101.3 kPa. The mole fraction solubility of 3,4dichloronitrobenzene in all studied solvents increased with increasing temperature, but the temperature increase increments varied. The mole fraction solubility of 3,4-dichloronitrobenzene in methanol, ethanol, methanol + water, and ethanol + water increased with increasing mass fractions of methanol or ethanol in the mixed solvent at a given temperature. The van’t Hoff equation, the modified Apelblat equation, and the λh equation were employed to fit the mole fraction solubility values for 3,4-dichloronitrobenzene in different solvents. The calculated solubility by the modified Apelblat equation showed the closest agreement with the experimental solubility data than the other two models. Furthermore, the thermodynamic properties for the studied solvents were calculated according to the measured solubility of 3,4-dichloronitrobenzene. The experimental solubility data and equations presented in this work can be used for 3,4dichloronitrobenzene purification in industry.

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AUTHOR INFORMATION

Corresponding Author

*Tel.: + 86 514 87975568. Fax: + 86 514 87975244. E-mail address: [email protected]. Notes

The authors declare no competing financial interest.

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REFERENCES

(1) Ishikura, T.; Fukushima, T. Process for Preparing 3-Chloro-4fluoronitrobenzene. EP Patent 0,307,481, November 24, 1993. (2) Xie, W. Y. Method for Coproducing 3-Chloro-4-fluoroaniline and 2,6-Dichlorofluobenzene. CN Patent 1,515,542, July 28, 2004. (3) Wei, Z. Y.; Chen, Z. Y. Preparation of 2,4-Dichlorofluorobenzene via 3,4-dichloronitrobenzene. Chin. J. Pharm. 1996, 27, 467−468. 3068

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