Determination and Correlation of Pyridazin-3-amine Solubility in Eight

Jul 30, 2012 - Guan Wang , Yongli Wang , Jie Zhang , Qinghua Luan , Youguang Ma ... Songgu Wu , Dongchen Cai , Jinxu Wang , Dejiang Zhang , Kaifei ...
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Determination and Correlation of Pyridazin-3-amine Solubility in Eight Organic Solvents at Temperatures Ranging from (288.05 to 333.35) K Xin-Xiang Cao,† Rui-Jian Tong,‡ Yan Zhao,§ Teng-Teng Lv,† Ya Song,† and Jing-Cai Yao*,† †

College of Chemistry and Chemical Engineering, ‡Life Science College, and §Physics and Electronic Information College, Luoyang Normal University, Luoyang 471022, People’s Republic of China ABSTRACT: Using a synthetic method, the solubility data of pyridazin3-amine were obtained in methanol, ethanol, 1-propanol, 2-propanol, 1butanol, 2-propanone, ethyl acetate, and aniline at temperatures ranging from (288.05 to 333.35) K at atmospheric pressure. The fusion enthalpy and melting point were measured by differential scanning calorimetry. Modified Apelblat, λh, and Wilson models of nonideal solution were used to correlate the measured solubility data, respectively. Among them, Apelblat and λh equations have satisfying fitting effects for the experimental solubility values in all selected solvents with the rootmean-square deviation being less than 1.58 %. The activity coefficients of pyridazin-3-amine and molar dissolution enthalpy, entropy, and Gibbs free energy of the solute in methanol, 1-propanol, and 2-propanol were calculated in accordance with the parameters of the Wilson model at experimental solubility points.

■

INTRODUCTION Pyridazin-3-amine (molecular formula C4H5N3; molar mass 9.51·10−2 kg·mol−1; CAS Registry No. 5469-70-5) is very useful as an intermediate for the preparation of 3-sulfanilamidopyridazine, which is a sulfa drug type with high bacteriostatic activity.1 In industry, pyridazin-3-amine is obtained by four steps.2 In the first step, a suspension consisting of 3-amino-6-chloropyridazine, palladium-charcoal catalyst, and sodium hydroxide in absolute ethyl alcohol is subjected to hydrogenation. In the second step, the mixture is filtered warm, and then excess hydrogen chloride is added before the filtrates are concentrated. In the third step, two crystallizations from absolute ethanol and absolute pentane produce white microcrystals of hydrochloride. In the fourth step, pyridazin-3-amine hydrochloride is converted to pyridazin-3-amine, and then transparent blades are obtained by crystallization of the crude product from ethyl acetate. Common solvents such as ethanol, methanol, 2propanone, ethyl acetate, and so forth are often used during the synthesis process. Therefore, the solubility data in these solvents are needed for this purpose. Moreover, the solubility data are also important physicochemical parameters influencing solution thermodynamics, crystallization kinetics, and crystal interface structure in processes of solution crystallization and further recrystallization.3−5 However, the solubility data of pyridazin-3-amine have not yet been reported in any solvents. In this work, the solubility of pyridazin-3-amine in methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-propanone, ethyl acetate, and aniline was measured from (288.05 to 333.35) K at atmospheric pressure. The modified Apelblat, Buchowski (λh), © 2012 American Chemical Society

and Wilson equations were selected to correlate the experimental solid−liquid equilibrium data. In addition the activity coefficients of pyridazin-3-amine and the molar dissolution enthalpy, entropy, and Gibbs free energy of of the solute in methanol, 1-propanol, and 2-propanol were estimated with the parameters of the Wilson model.

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EXPERIMENTAL SECTION Materials. Pyridazin-3-amine (mass fraction purity >0.98) supplied by Changzhou Harvest Chemistry Co., Ltd., China, was recrystallized from ethanol several times to get a purified sample. The mass fraction purity of pyridazin-3-amine recrystallized was analyzed by high-performance liquid chromatography (HPLC; type Shimadzu LC-10AT, Japan) and determined to be no less than 0.995. All of the solvents including methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-propanone, ethyl acetate, and aniline used in the experiments are analytical reagent grade, provided by Tianjin Chemical Reagent Co., Ltd. of China, of purity more than 0.995 mass fraction. Detailed information of all substances used in this study is listed in Table 1. Melting Properties Measurements. The melting point Tm and heat of fusion ΔfusH of pyridazin-3-amine were obtained by a differential scanning calorimetric instrument (Pyris-Diamond DSC, PerkinElmer, USA) under a nitrogen atmosphere. The temperature and heat flow precalibration of Received: May 31, 2012 Accepted: July 18, 2012 Published: July 30, 2012 2360

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measured solutions were determined by a laser beam penetrating the glass vessel. At the beginning of an experiment, a predetermined mass of solid solute pyridazin-3-amine and a known mass of selected solvent were weighed with an electronic analytical balance (uncertainty of ± 0.0001 g, type Sartorius BS210S, Germany) and then were placed to the vessel. The liquid−solid system was being continuously stirred at a fixed temperature. When solid particles of pyridazin-3-amine just disappeared, the light intensity of the laser beam penetrating the mixture in vessel reached its peak, and then an additional pyridazin-3-amine [(2 to 5) mg] was put into the vessel. Now, if the additional pyridazin-3-amine disappeared, that is, the light intensity of the laser beam reached the maximum value again within 60 min, an additional pyridazin-3-amine [(2 to 5) mg] was put into the vessel again. This process was repeated a few times until the last addition was not dissolved completely in 60 min; namely, when the intensity of the laser beam was no more than 90 % of the maximum, the mixture was considered as reaching phase equilibrium. By this time, the total mass of pyridazin-3-amine consumed was recorded. The saturated experimental solubility x1 of solute pyridazin3-amine can be obtained by eq 1.

Table 1. Sources and Purity of the Materials materials

mass fraction purity

pyridazin-3amine methanol (AR)a

≥0.995

ethanol (AR)

≥0.997

1-propanol (AR) 2-propanol (AR) 1-butanol (AR)

≥0.995

ethyl acetate (AR) 2-propanone (AR) aniline (AR)

≥0.995

a

≥0.995

≥0.995 ≥0.995

≥0.995 ≥0.995

sources Changzhou Harvest Chemistry Co., Ltd., China Tianjin Chemical Reagent Co., Ltd., China Tianjin Chemical Reagent Co., Ltd., China Tianjin Chemical Reagent Co., Ltd., China Tianjin Chemical Reagent Co., Ltd., China Tianjin Chemical Reagent Co., Ltd., China Tianjin Chemical Reagent Co., Ltd., China Tianjin Chemical Reagent Co., Ltd., China Tianjin Chemical Reagent Co., Ltd., China

AR means analytical reagent.

the instrument were performed by using the phase-transition temperature and phase-transition enthalpy of National Institute of Standards and Technology (NIST) reference materials (indium: ΔfusH = 28.45 J·g−1, Tm = 429.75 K; stannum: ΔfusH = 60.21 J·g−1, Tm = 505.10 K) before use. Approximately 5 mg of pyridazin-3-amine powder was added to a DSC pan. Then the sample was heated at a 2 K·min−1 heating rate over the temperature range from (413.15 to 473.15) K. Uncertainties of the measurements were ± 0.5 K for the temperature and no more than 5 % for the enthalpy of fusion. Solubility Measurements. The solubility of pyridazin-3amine was determined by a synthetic method.6−8 The procedure was described by our co-workers in detail in previous works9,10 and was improved slightly in this work. As shown in Figure 1, the measurement of the solubility was

x1 =

m1/M1 m1/M1 + m2 /M 2

(1)

where m1 and m2 respectively denote the mass of pyridazin-3amine and the solvent selected and M1 and M2 represent respective molecular weights. Each solubility data point was determined three or more times, and the relative uncertainties of measurements were below 1 mol %.

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THERMODYNAMIC MODELS Modified Apelblat Equation. The absolute temperature T dependence of the experimental solubility (xexptl) of pyridazin3-amine in selected solvents can be well-correlated by the modified Apelblat equation derived from the Williamson equation.11,12 ln x1 = A +

B + C ln T T

(2)

where A, B, and C are adjustable empirical constants. Buchowski (λh) Equation. Buchowski et al.13 used the λh equation to represent the solubility of solid solute in liquid− solid phase equilibrium systems originally. The model has an excellent effect for correlating the solubility and the temperature. The λh equation is given as

Figure 1. Schematic diagram of the measuring equipment of experimental solubility data: A, jacketed glass vessel; B, dropping funnel of constant pressure; C, mercury-in-glass thermometer; D, reflux condenser; E, magnetic stirrer; F, super thermostatic water bath; G, laser transmitter; H, photoelectric transformer; I, control and digital display.

⎡ ⎛1 λ(1 − x1) ⎤ 1 ⎞ ln⎢1 + ⎥ = λh⎜ − ⎟ x1 Tm ⎠ ⎦ ⎣ ⎝T

(3)

where Tm is the normal melting temperature of pyridazin-3amine and λ and h are two constants of the λh model. λ is identified as the association number of solute molecules in associating solution, and its value is a reflection of the nonideality of the solution. h equals the ratio of the enthalpy of solution to the gas constant R, so it can be used to estimate the enthalpy of solution.14 Wilson Model. At phase equilibrium, there is a universal solubility model according to basic thermodynamic theory,15

implemented in a 200 mL jacketed glass vessel on a magnetic stirrer (type 85-2, China). The stationary temperature was maintained by water in the outer jacket circulated from a thermostatic water bath (type CS501, China). A condenser directly linked to the vessel was used to prevent solvent evaporation. The temperatures were measured precisely by a mercury-in-glass thermometer (uncertainty of ± 0.05 K, type WLB, China) inserted into the solutions. Equilibrium points of 2361

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Table 2. Solubility of Pyridazin-3-amine in Methanol, Ethanol, 1-Propanol, 2-Propanol, 1-Butanol, 2-Propanone, Ethyl Acetate, and Aniline T/K

103 x1

103 xApel

102 RDApel

288.15 293.05 298.15 303.25 308.15 313.15 318.25 323.55 328.15

35.64 39.81 45.48 51.97 59.58 67.51 75.98 86.50 98.06

35.38 40.13 45.74 52.11 59.03 67.02 76.24 87.12 97.75

0.73 −0.80 −0.57 −0.27 0.92 0.73 −0.34 −0.72 0.32

288.35 294.05 298.75 303.15 308.25 313.35 318.35 323.35 328.35 333.15

19.29 21.30 23.65 26.61 30.62 34.88 40.93 49.22 60.23 71.31

19.30 21.39 23.67 26.35 30.26 35.25 41.46 49.34 59.37 71.60

−0.05 −0.42 −0.08 0.98 1.18 −1.06 −1.29 −0.24 1.43 −0.41

288.45 293.05 298.35 302.85 308.15 313.05 318.35 322.95 327.95 333.15

16.10 18.53 22.00 25.49 29.30 35.08 40.12 46.14 51.87 60.18

16.00 18.62 22.07 25.40 29.83 34.48 40.16 45.69 52.38 60.17

0.62 −0.49 −0.32 0.35 −1.81 1.71 −0.10 0.98 −0.98 0.02

288.15 298.15 303.55 308.45 312.85 317.75 323.25 328.05 332.95

12.18 17.20 20.26 23.32 27.69 31.54 37.27 41.24 46.48

12.12 17.17 20.48 23.86 27.23 31.37 36.51 41.46 46.96

0.49 0.17 −1.09 −2.32 1.66 0.54 2.04 −0.53 −1.03

289.35 293.35 298.05 303.15 308.15 313.15 318.05 322.65 327.95 332.95

10.53 12.60 16.96 21.80 26.69 32.44 37.10 42.00 46.91 51.90

10.29 13.09 16.91 21.61 26.67 32.01 37.30 42.14 47.31 51.58

2.28 −3.89 0.29 0.87 0.07 1.33 −0.54 −0.33 −0.85 0.62

288.45 293.15 298.65 302.75 307.15 312.95

2.28 2.75 3.24 3.83 4.34 5.22

2.28 2.73 3.31 3.80 4.35 5.14

0.00 0.73 −2.16 0.78 −0.23 1.53

103 xλh

102 RDλh

103 xwil

102 RDwil

35.65 39.81 45.47 51.96 59.58 67.51 75.98 86.50 98.06

−0.03 0.00 0.02 0.02 0.00 0.00 0.00 0.00 0.00

34.80 39.98 45.97 52.62 59.69 67.62 76.52 86.69 96.34

2.36 −0.42 −1.08 −1.26 −0.18 −0.16 −0.70 −0.22 1.75

19.33 21.31 23.64 26.59 30.60 34.86 40.91 49.21 60.25 71.33

−0.21 −0.05 0.04 0.08 0.07 0.06 0.05 0.02 −0.03 −0.03

17.26 20.83 24.21 27.76 32.39 37.63 43.43 49.95 57.25 65.07

10.52 2.18 −2.34 −4.32 −5.77 −7.88 −6.10 −1.48 4.96 8.74

16.10 18.53 22.00 25.49 29.29 35.09 40.12 46.15 51.87 60.18

0.00 0.00 0.00 0.00 0.03 −0.03 0.00 −0.02 0.00 0.00

15.97 18.62 22.08 25.42 29.86 34.51 40.18 45.68 52.36 60.12

0.75 −0.46 −0.36 0.28 −1.92 1.64 −0.15 1.00 −0.94 0.11

12.18 17.20 20.26 23.31 27.70 31.55 37.27 41.24 46.47

0.00 0.00 0.00 0.04 −0.04 −0.03 0.00 0.00 0.02

12.26 17.13 20.34 23.67 27.02 31.20 36.50 41.70 47.63

−0.61 0.41 −0.43 −1.52 2.39 1.08 2.06 −1.12 −2.47

10.51 12.58 16.97 21.83 26.71 32.47 37.12 42.00 46.89 51.86

0.19 0.16 −0.06 −0.14 −0.07 −0.09 −0.05 0.00 0.04 0.08

11.37 13.37 16.15 19.78 24.09 29.30 35.45 42.38 51.98 62.95

−7.97 −6.15 4.80 9.29 9.74 9.70 4.45 −0.89 −10.81 −21.29

2.26 2.75 3.24 3.85 4.35 5.24

0.88 0.00 0.00 −0.52 −0.23 −0.38

1.98 2.41 3.00 3.52 4.17 5.17

12.95 12.52 7.27 8.03 3.93 0.99

Methanol

Ethanol

1-Propanol

2-Propanol

1-Butanol

Ethyl Acetate

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Table 2. continued T/K

103 x1

103 xApel

102 RDApel

318.65 322.65 328.25 332.35

5.88 6.65 7.38 8.13

5.97 6.57 7.45 8.10

−1.53 1.20 −0.95 0.37

288.25 293.15 298.35 303.05 308.35 313.25 317.85 323.35 328.05

6.80 8.01 9.07 10.23 11.97 13.29 14.78 16.86 18.75

6.85 7.89 9.11 10.32 11.82 13.33 14.87 16.86 18.70

−0.74 1.50 −0.44 −0.88 1.25 −0.30 −0.61 0.00 0.27

288.05 293.25 298.35 302.95 308.45 313.15 318.15 323.45 328.15 333.35

23.10 28.85 34.71 41.87 48.69 55.89 62.26 69.26 76.03 82.46

23.09 28.86 35.13 41.21 48.83 55.50 62.58 69.86 75.95 82.13

0.04 −0.03 −1.21 1.58 −0.29 0.70 −0.51 −0.87 0.11 0.40

103 xλh

102 RDλh

103 xwil

102 RDwil

Ethyl Acetate 5.88 6.65 7.37 8.11

0.00 0.00 0.14 0.25

6.34 7.30 8.85 10.16

−7.86 −9.82 −19.94 −24.95

6.79 8.02 9.07 10.22 11.98 13.30 14.78 16.86 18.75

0.15 −0.12 0.00 0.10 −0.08 −0.08 0.00 0.00 0.00

5.90 7.06 8.48 11.91 11.72 13.96 16.16 19.15 22.06

13.27 11.90 6.46 −16.45 2.06 −5.03 −9.33 −13.54 −17.64

23.08 28.85 34.72 41.89 48.71 55.91 62.27 69.26 76.02 82.43

0.09 0.00 −0.03 −0.05 −0.04 −0.04 −0.02 0.00 0.01 0.04

25.04 29.52 34.50 39.54 46.29 52.73 60.34 69.29 78.06 88.74

−8.39 −2.31 0.61 5.58 4.93 5.64 3.09 −0.04 −2.67 −7.61

2-Propanone

Aniline

Figure 2. Solubility of pyridazin-3-amine in eight studied solvents: ■, methanol; □, aniline; ▲, ethanol; ▽, 1-propanol; ●, 1-butanol; ☆, 2propanol; ∗, 2-propanone; ◆, ethyl acetate. Solid line, calculated data based on the modified Apelblat equation; dashed line, calculated data based on the λh equation; dash−dotted line, calculated data based on the Wilson equation.

ln x1γ1 =

⎞ ΔtpH ⎛ 1 Ttp 1 ⎞ ΔCp ⎛ Ttp ⎜⎜ − ⎟⎟ − − + 1⎟ ⎜ln R ⎝ Ttp T⎠ R ⎝ T T ⎠ ΔV − (P − Ptp) (4) RT

constant pressure ΔCp and pressure are very little; they can be ignored. The fusion temperature Tm is close to the triple point temperature,Ttp, so Ttp and enthalpy of triple point ΔtpH often be replaced to Tm and the enthalpy of melting ΔfusH. Equation 4 can be simplified as

where γ1 represents the activity coefficient of solute and ΔV is the volume difference between phases of solid and liquid. The effects of the differences upon molar heat capacity under

ln x1 = 2363

ΔfusH ⎛ 1 1⎞ − ⎟ − ln γ1 ⎜ R ⎝ Tm T⎠

(5)

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Table 3. Parameters of Modified Apelblat, λh, and Wilson Models for Pyridazin-3-amine in Eight Organic Solvents and the Root-Mean-Square Deviations of Measured Solubility Data with the Calculated Results λh

modified Apelblat

Wilson

solvent

A

B

C

102 rmsdApel

λ

h

102 rmsdλh

Δλ12

Δλ21

102 rmsdwil

methanol ethanol 1-propanol 2-propanol 1-butanol ethyl acetate 2-propanone aniline

−88.205 −460.193 −15.419 44.991 563.904 174.939 21.135 338.668

1853.164 18605.110 −1875.104 −4708.093 −29155.297 −10644.438 −3199.482 −17995.364

13.849 69.158 3.140 −5.838 −82.524 −25.443 −2.652 −49.436

0.64 0.87 0.95 1.31 1.58 1.19 0.82 0.76

0.540 0.470 0.422 0.344 0.895 0.051 0.084 0.615

4233.437 5859.586 6469.593 8053.170 4080.718 50409.016 25361.290 4332.952

0.01 0.08 0.01 0.02 0.09 0.27 0.05 0.01

−4082.770 −1310.287 −712.873 −88.169 6387.929 4925.441 1576.079 −1421.961

9164.002 6234.258 9414.746 192383.220 −2312.266 227418.311 75716.923 139652.308

1.16 6.13 0.96 1.55 9.95 12.79 11.75 4.88

(23)].19 For the special case of aniline, it was assumed that the chemical structure similarity between the solute and the solvent due to the amino group largely improved the solubility, corresponding to the principle of “like dissolves like”. Regression Analysis of Solubility Data. The values of model parameters for modified Apelblat, λh, and Wilson equations were obtained through regression of the experimental solubility data and are listed respectively in Table 3 together with root-mean-square deviations (rmsd's), described as

In this study, a local composition model, the Wilson equation, was used to calculate γ1. This model has been successfully applied to the vapor−liquid equilibrium and liquid−liquid equilibrium systems and also for the estimation of solubilities in solid−liquid equilibrium systems.16,17 For a binary system, this model is given as ⎞ ⎛ Λ 21 Λ12 ln γ1 = −ln(x1 + Λ12x 2) + x 2⎜ − ⎟ x 2 + Λ 21x1 ⎠ ⎝ x1 + Λ12x 2 (6)

⎡ 1 rmsd = ⎢⎢ N ⎣

where ν2 ⎛ λ12 − λ11 ⎞ ⎟ exp⎜ − RT ⎠ ν1 ⎝ ⎛ λ − λ 22 ⎞ ν ⎟ Λ 21 = 1 exp⎜ − 21 RT ⎠ ν2 ⎝

Λ12 =

and

1/2

(9)

where N denotes the number of solubility data points measured in one solvent; xcalcd and xexp 1,i 1,i refer to the calculated solubility and experimental solubility, respectively. The relative deviations (RD's) between the calculated solubility and the experimental solubility are given in Table 2.

(7)

in eqs 6 and 7, x2 is the mole fraction of the solvent, Δλ12(= λ12 − λ11) and Δλ21(= λ21 − λ22) are two binary interaction parameters unrelated to composition and temperature, and ν1 and ν2 denote the molar volumes of pure solute and pure solvent, respectively.

RD =

■

calcd x1,exp i − xi

x1,exp i

(10)

From Tables 2 and 3, we can see all RD's and rmsd's of modified Apelblat and λh models are less than 3.92 % and 1.58 %, but the Wilson model is only fit for regressing the measured solubility data of solute in methanol, 1-propanol, and 2propanol with the rmsd's being 1.16 %, 0.96 %, and 1.55 %, respectively. The calculated values of activity coefficients of pyridazin-3amine in methanol, 1-propanol, and 2-propanol were obtained from eq 6. The results are shown in Table 4 and Figure 3, and it can be seen that at the same temperature, contrary to the change trends of the solubility of pyridazin-3-amine, the values of activity coefficients increase with the decreasing polarities of the three solvents. This means that repulsive interactions existing between pyridazin-3-amine and molecules of the solvents increase with the rising polarities of the solvents. Prediction of Dissolution Properties. For a nonideal solution, the Gibbs free energy of dissolution ΔdG, enthalpy of dissolution ΔdH, and entropy of dissolution ΔdS can be calculated by the relation20

RESULTS AND DISCUSSION Property Evaluation of Pure Components. The melting point Tm and heat of fusion ΔfusH of pyridazin-3-amine analyzed by DSC are 441.9 ± 0.5 K and 24 ± 1 kJ·mol−1, respectively. Using the property of classical thermodynamics, ΔfusS = ΔfusH /Tm

⎛ x calcd − x exp ⎞2 ⎤ ∑ ⎜⎜ 1,i exp 1,i ⎟⎟ ⎥⎥ x1, i ⎠⎦ i=1 ⎝ N

(8)

The entropy of fusion ΔfusS of pyridazin-3-amine can be obtained, and its value is 53.5 J·(mol·K)−1. The mole volume of pyridazin-3-amine is 78.21 cm3·mol−1, which was measured at 293.15 K using pycnometry.18 The values of the molar volumes for the solvents used in this work are taken from the literature.19 Solubility Data of Pyridazin-3-amine. The solubility data of pyridazin-3-amine in methanol, ethanol, 1-propanol, 2propanol, 1-butanol, 2-propanone, ethyl acetate, and aniline at different temperatures are reported in Table 2 and shown in Figure 2. For each solvent we selected, the solubility of pyridazin-3-amine increases with the rise of temperature. The solubilities are ranked as methanol > aniline > ethanol > 1propanol > 1-butanol > 2-propanol > 2-propanone > ethyl acetate, which are in complete accordance with their polarity order except for aniline [polarity: methanol (76.2) > ethanol (65.4) > 1-propanol (61.7) > 1-butanol (60.2) > 2-propanol (54.6) > aniline (42.0) > 2-propanone (35.5) > ethyl acetate

Δd M = Δmix M id + ΔfusM + ΔME

(11)

where M = G, H, and S, ΔmixMid is the change of mixing property for an ideal solution, ME is the excess property, and ΔfusM is the change of dissolving property of solute. During the phase transition of solute, the system is in equilibrium, so ΔfusG = 0. 2364

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Δmix S id = −R(x1 ln x1 + x 2 ln x 2)

Table 4. Dissolution Enthalpy, Entropy, Gibbs Free Energy, and Activity Coefficients of Solute in Methanol, 1-Propanol, and 2-Propanol, Based on the Wilson Model T/K 288.15 293.05 298.15 303.25 308.15 313.15 318.25 323.55 328.15 288.45 293.05 298.35 302.85 308.15 313.05 318.35 322.95 327.95 333.15 2637 2639 2640 2642 2643 2644 2646 2647 2649

ΔdH/J·mol−1 23515.00 23497.53 23477.68 23456.07 23433.62 23409.01 23382.12 23352.31 23324.93 23633.70 23632.61 23631.25 23630.02 23628.49 23627.01 23625.36 23623.91 23622.33 23620.74 23640.79 23640.38 23640.10 23640.79 23639.82 23639.54 23639.19 23638.76 23638.33

ΔdS/J·mol−1·K−1 Methanol 62.87 62.96 63.07 63.18 63.29 63.40 63.52 63.64 63.74 1-Propanol 62.37 62.44 62.53 62.61 62.71 62.81 62.93 63.03 63.16 63.29 2-Propanol 62.25 62.38 62.46 62.25 62.54 62.62 62.70 62.81 62.91

ΔdG/J·mol−1

γ1

−2828.69 −2920.83 −3020.53 −3124.08 −3227.14 −3335.84 −3450.27 −3572.81 −3682.04

0.927 0.952 0.978 1.002 1.026 1.049 1.073 1.096 1.115

−2568.94 −2631.44 −2706.39 −2772.62 −2853.81 −2932.04 −3020.19 −3099.75 −3189.5 −3286.49

2.041 2.045 2.048 2.050 2.051 2.050 2.049 2.046 2.042 2.036

−2525.86 −2652.81 −2725.31 −2793.65 −2857.16 −2930.36 −3015.72 −3093.04 −3174.74

2.633 2.624 2.617 2.610 2.603 2.594 2.582 2.570 2.556

(13)

On the basis of the Wilson model, the excess properties can be expressed by22,23 GE = RT (x1 ln γ1 + x 2 ln γ2) =−x1RT (x1 + x 2 Λ12) − x 2RT (x 2 + x1Λ 21)

(14)

⎡ ∂(GE /T ) ⎤ H E = − T 2⎢ ⎥ ⎣ ∂T ⎦ ⎛ Δλ12 Λ12 Δλ 21Λ 21 ⎞ = x1x 2⎜ + ⎟ x 2 + x1Λ 21 ⎠ ⎝ x1 + x 2 Λ12

S E = (HE − GE)/T

(15) (16)

The values of ΔdG, ΔdH, and ΔdS of pyridazin-3-amine in methanol, 1-propanol, and 2-propanol at measured solubility points were obtained and are shown in Table 4. The relation between Gibbs free energy of dissolution and temperature is also shown in Figure 4. The results show that the values of ΔdG

Figure 4. Gibbs free energy of dissolution of pyridazin-3-amine based on the Wilson equation. □, methanol; ▲, 1-propanol; ☆, 2-propanol.

are all negatives. It indicates the pyridazin-3-amine dissolving in the three organic solvents are spontaneous processes. In addition, corresponding to classical thermodynamics theory, the lower ΔdG values are, the more pyridazin-3-amine the solvent can hold.

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CONCLUSIONS The experimental solubility data of pyridazin-3-amine were measured in methanol, ethanol, 1-propanol, 2-propanol, 1butanol, 2-propanone, ethyl acetate, and aniline at temperatures ranging from (288.05 to 333.35) K at atmospheric pressure. The melting point Tm and heat of fusion ΔfusH of pyridazin-3amine were obtained by a differential scanning calorimetric instrument (DSC). The solubility of the compound improves with the increase of temperature and is dependent on the polarities and the structure of the solvents we studied, in the order of methanol > aniline > ethanol > 1-propanol > 1-butanol > 2-propanol > 2-propanone > ethyl acetate. The experimental solubility data of pyridazin-3-amine were well-fitted by the modified Apelblat and λh models. The Wilson model is only fit for regressing the measured solubility data of

Figure 3. Relations between the activity coefficient of pyridazin-3amine and absolute temperature. □, methanol; ▲, 1-propanol; ☆, 2propanol.

For the ideal solution, ΔmixHid = 0, other mixing properties of a binary mixture can be obtained using the relations21 Δmix Gid = RT (x1 ln x1 + x 2 ln x 2)

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dx.doi.org/10.1021/je300517q | J. Chem. Eng. Data 2012, 57, 2360−2366

Journal of Chemical & Engineering Data

Article

[2,3-b]pyrazine in Methanol, Ethanol, and 2-Propanol. Ind. Eng. Chem. Res. 2011, 50, 11755−11762. (18) Redding, T. E.; Hannam, K. D.; Quideau, S. A.; Devito, K. J. Particle Density of Aspen, Spruce, and Pine Forest Floors in Alberta, Canada. Soil Sci. Soc. Am. J. 2005, 69, 1503−1506. (19) Smallwood, I. M. Handbook of organic solvent properties; Arnold: London, 1996. (20) Bourne, J. R.; Davey, R. J. The role of solvent-solute interactions in determining crystal growth mechanisms from solution. J. Cryst. Growth. 1976, 36, 278−296. (21) Smith, J. M.; Ness, H. C. V.; Abbott, M. M. Introduction to Chemical Engineering Thermodynamics; McGraw-Hill: New York, 2001. (22) Orye, R. V.; Prausnitz, J. M. Multicomponent Equilibria-The Wilson Equation. Ind. Eng. Chem. 1965, 57, 18−26. (23) Gow, A. S. Calculation of Vapor−Liquid Equilibria from Infinite-Dilution Excess Enthalpy Data using the Wilson or NRTL Equation. Ind. Eng. Chem. Res. 1993, 32, 3150−3161.

solute in methanol, 1-propanol, and 2-propanol. The dissolution properties of pyridazin-3-amine in methanol, 1propanol, and 2-propanol were calculated based on the Wilson equation. The results show that the processes of pyridazin-3amine dissolving in the three organic solvents are spontaneous.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Tel.: 0086-379-65526007. Fax: 0086-379-65523821. Funding

We are grateful to the financial support from the Natural Science Foundation of Henan province of China (Nos. 0511022600 and 092102310075). Notes

The authors declare no competing financial interest.

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