Article pubs.acs.org/jced
Solubility of Benzyl Disulfide in Five Organic Solvents between (283.45 and 333.15) K Yana Wang, Shuixiang Fu, Yinxia Jia, Chao Qian,* and Xinzhi Chen Key Laboratory of Biomass Chemical Engineering of Ministry of Education, Zhejiang University, Hangzhou 310027, China ABSTRACT: The solubility data of benzyl disulfide were measured using the synthetic method and laser monitoring technique under atmospheric pressure in five solvents (ethanol, n-hexane, ethyl acetate, toluene, and chloroform), with the temperature ranging from (283.45 to 333.15) K. The experimental data in each solvent were fitted by the modified Apelblat equation with good agreement. For all of the experimental solubility data in five solvents, the root-mean-square was less than 0.52 %, whereas the average absolute relative error was less than 2.0 %.
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INTRODUCTION Benzyl disulfide (CAS Registry No. 150-60-7) is particularly useful as a kind of lubricating oil additive, whose molecular structure is illustrated in Figure 1.1 In the chemical industry,
EXPERIMENTAL SECTION Materials. Benzyl disulfide was obtained from Jiangxi Renming Pharmaceutical Chemicals Ltd. and was recrystallized two times from ethanol to yield purified samples (mass fraction > 0.995, determined by HPLC). The solvents (ethanol, n-hexane, ethyl acetate, toluene, and chloroform) of analytical grade were purchased from Sinopharm Chemical Reagent Co. Ltd., which worked without any purification process, and the detailed information of the solvents is show in Table 1.
Table 1. Detailed Information of the Solvents Figure 1. Chemical structure of benzyl disulfide.
mass fraction
CAS registry no.
ethanol
>0.997
64-17-5
n-hexane
>0.995
110-54-3
ethyl acetate
>0.995
141-78-6
toluene
>0.995
108-88-3
chloroform
>0.996
67-66-3
solvents
purification is an important process to produce high quality benzyl disulfide, and crystallization is one of the most useful ways of purification. Crystallization is usually used to enable efficient isolation of the products, in which the solubilities in a variety solvents as well as the temperature are crucial.2−4 Thereby, the study of the solubility data of benzyl disulfide in different solvents is especially necessary in industry. According to the study, we choose five organic solvents (ethanol, n-hexane, ethyl acetate, toluene, and chloroform) to measure the solubilities of benzyl disulfide, which are practical in crystallization process and have never been reported previously. The five organic solvents have different polarities and are widely used in producing benzyl disulfide in organic synthesis.5−7 Moreover, the measurements of the solid−liquid equilibrium and the foundation of thermodynamic models are crucial in the study. The Apelblat equation, Buchowski (λh) equation, NRTL equation, Hansen equation, and Wilson equation are usually used to study the solubilities of solids.8,9 The modified Apelblat equation is selected to be the equation which correlates the experimental data. Actually, the modified Apelblat equation is developed from the Van’t Hoff equation, and it is more advised when more than five data points involving a relatively wide range of temperatures are convenient.10 © 2013 American Chemical Society
sources Sinopharm Chemical Reagent Co. Ltd. Shanghai Jingchun Reagent Co. Ltd. Sinopharm Chemical Reagent Co. Ltd. Sinopharm Chemical Reagent Co. Ltd. Sinopharm Chemical Reagent Co. Ltd.
Apparatus and Procedure. Benzyl disulfide’s solubility data was measured using the synthetic method11,12 and laser monitoring technique under atmospheric pressure. Referring to the experiment of measuring solubilities, a set of experimental facility was used, which was illustrated in Figure 2. A jacketed glass vessel was used to dissolve the solute in the experiment, whose temperature was controlled by a thermostat water bath (type CS501, China). The real temperature of solution was determined by a microthermometer with uncertainty of 0.01 K in the vessel. The mass of the solutes and solvents were measured with an electronic analytical balance (type AR2140, Received: April 6, 2013 Accepted: July 31, 2013 Published: August 20, 2013 2483
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Figure 2. 1, signal display; 2, laser acceptor; 3, precise mercurial thermometer; 4, feed inlet; 5, jacked dissolution vessel; 6, condenser; 7, laser generator; 8, magnetic stirring apparatus; 9, thermostat.
China, ± 0.1 mg), and the solution was stirred constantly with an electromagnetic agitator. The condenser was used to prevent the solvents from evaporating. At the beginning of the experiment, a certain mass of benzyl disulfide was put into the vessel with the solvent and was stirred continuously under a fixed temperature for 1 h. The dissolution of benzyl disulfide was determined by laser monitoring technique, which consisted of three parts (laser generator, laser acceptor, and signal display). At first, a part of the solid which was not dissolved in the solution led to reduction of the laser light. Then, when the last solid disappeared, the penetrated light reached the maximum. The next step was to add a known mass (about (1 to 5) mg) of the benzyl disulfide into the container until the solution did not dissolve it anymore. Each process of adding solid lasted more than 30 min, and the quantity of solute was recorded. After getting the solubility data at a fixed temperature, the temperature of the solution was changed by the thermostat water bath, and the experimental steps were repeated to get additional solubility data. The mole fraction of benzyl disulfide was calculated as follows: x1 =
m1/M1 m1/M1 + m2 /M 2
where x stands for the mole fraction solubility of benzyl disulfide and T is the absolute temperature. The dimensionless constants A, B, and C are presented in Table 3. The root-meansquare (rmsd) is defined as follows:15 ⎡ ∑N (x cal − x )2 ⎤1/2 i i ⎥ rmsd = ⎢ i = 1 ⎢⎣ ⎥⎦ N
where N represents the number of experimental points, xical is the solubility data which is calculated from the modified Apelblat equation, and xi is the mole fraction solubility data of benzyl disulfide in each experiment. The average absolute relative error σ is defined as σ=
1 N
n
∑ i=1
xical − xi × 100% xi
(4)
As it is shown in Figure 3, some results can be seen through the solubility data of benzyl disulfide. First, the solubilities of benzyl disulfide in five solvents (ethanol, n-hexane, ethyl acetate, toluene, and chloroform) increase with the increasing of temperature. What’s more, it is dissolved a little more for benzyl disulfide in chloroform than in others, whereas it is lowest in ethanol. The solubility data of the solute in five solvents is ranked as ethanol < n-hexane < ethyl acetate < toluene < chloroform. It is presented in Table 2 that the solubility changes are more pronounced with temperature in ethanol and less in n-hexane, and they are the lowest in ethyl acetate, toluene, and chloroform. Thereby, ethanol is the most proper solvent in separation and purification of benzyl disulfide in industry. According to the value of the average absolute relative error which is less than 2.0 %, the experimental solubility data can be regressed by eq 2 and are fitted with it very well.
(1)
where m1 and m2 respectively are the mass of benzyl disulfide and solvent (ethanol, n-hexane, ethyl acetate, toluene, and chloroform). M1 and M2 are the molecular masses of benzyl disulfide and solvent, respectively. Each experiment in every kind of solvent was run three times with reasonable consequences, while the uncertainty of the experiment was less than 2.0 %.
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RESULTS AND DISCUSSION The mole fraction solubilities of benzyl disulfide in a variety of solvents (ethanol, n-hexane, ethyl acetate, toluene, and chloroform) with the temperature ranging from (283.45 to 333.15) K are presented in Table 2. The temperature dependence of the solubilities in each solvent are fitted by the modified Apelblat equation.10,13,14 ln x = A + B /(T /K ) + C ln(T /K )
(3)
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CONCLUSIONS The solubility data of benzyl disulfide were measured using the synthetic method and laser monitoring technique under atmospheric pressure, with the temperature ranging from (283.45 to 333.15) K. According to Figure 3, the solubility of the solute goes up with an increase in temperature, and it reaches the maximum in the chloroform and a minimum in
(2) 2484
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Table 2. Experimental Mole Fraction Solubilities of Benzyl Disulfide in Selected Solvents with the Temperature Range from (283.45 to 333.15) K and Pressure p = 0.1 MPaa T/K
103 x
284.70 289.45 294.45 299.55 303.25 308.25
0.1675 0.3985 0.9047 1.903 3.014 5.239
284.25 288.35 294.45 298.25 303.65 309.05
0.9219 1.902 4.477 7.394 13.66 22.28
285.55 289.95 293.65 298.80 303.65 308.40
33.17 50.00 66.72 96.25 130.8 164.0
283.45 288.16 292.65 299.35 303.15 308.65
52.11 76.90 102.8 161.9 197.8 248.4
284.95 288.75 292.75 298.65 302.60 308.15
101.7 131.4 159.7 208.5 246.2 291.5
εb/%
T/K
Ethanol −0.2822 313.05 0.8027 318.05 0.5297 323.25 −1.046 328.15 −0.5575 333.05 −0.9410 n-Hexane 3.778 314.45 −2.835 318.25 −0.9465 323.05 −2.589 328.15 −2.335 332.95 2.314 Ethyl Acetate 1.929 313.15 −0.6115 318.35 −0.3205 323.05 −1.100 328.25 −2.677 333.05 −0.9327 Toluene 1.000 313.45 −0.7295 318.05 1.866 323.35 −2.619 327.95 −2.657 333.15 −0.2533 Chloroform 2.585 312.95 −1.876 318.05 −0.9602 323.25 −0.8041 328.15 −1.596 332.65 1.179
103 x
εb/%
8.023 11.88 16.23 20.52 24.47
0.9980 0.1619 0.8610 0.3099 −0.8738
34.86 47.39 65.26 84.78 106.3
3.462 0.8594 −0.5020 0.3244 −1.796
198.1 231.6 268.4 300.5 334.9
0.7328 3.303 1.611 1.062 −3.154
294.2 338.0 389.5 434.6 481.3
1.302 2.208 1.840 0.2032 −2.335
338.0 386.5 435.1 475.9 516.4
1.041 0.9752 0.4786 0.2849 −1.405
Figure 3. Experimental solubilities of benzyl disulfide in five solvents: ●, ethanol; ○, n-hexane; Δ, ethyl acetate; ★, toluene; ☆, chloroform and fitted lines.
fundamental data in the manufacturing and separating processes of benzyl disulfide.
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AUTHOR INFORMATION
Corresponding Author
*Tel: +86-571-87951615. Fax: +86-571-87951742. E-mail:
[email protected]. Funding
The authors are grateful for the financial support from the National Natural Science Foundation of China (21006087), Research Fund for the Doctoral Program of Higher Education of China (20120101110062), and The Low Carbon Fatty Amine Engineering Research Center of Zhejiang Province (2012E10033). Notes
The authors declare no competing financial interest.
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a
Standard uncertainties u are u(T) = 0.01 K, ur(p) = 0.05,and ur(x) = 0.01. bε = (xcal − x)/x × 100 % where x is the experimental mole fraction solubility data and xcal is the calculated mole fraction solubility data.
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ethanol. The solubility changes are more pronounced with temperature in ethanol than in other solvents. The values of rmsd are all less than 0.52 % in each experiment, and the experimental data is in very good agreement with the modified Apelblat equation. Consequently, the study concerning the solubility of benzyl disulfide in different solvents provides
Table 3. Parameters of the Modified Apelblat Equation and Deviations for Benzyl Disulfide in Selected Solvents (0.1 MPa) solvent
A
B
C
R2 a
σ/%
rmsd/%
ethanol n-hexane ethyl acetate toluene chloroform
1814.4 1316.4 911.04 738.75 473.67
−91503 −68070 −45642 −37320 −24389
−265.73 −191.83 −133.45 −108.03 −69.058
0.99997 0.99971 0.99919 0.99922 0.99915
0.66945 1.9765 1.5849 1.5466 1.1986
0.0084667 0.072782 0.44190 0.51874 0.34365
N 2 2 N 2 R = [ΣNi=1(xi − x)(T ̅ i − T̅ )] /[Σi=1(xi − x)̅ Σi=1(Ti − T̅ ) ] where xi is one of the mole fraction solubility data, x̅ is the average of the mole fraction solubility data, and Ti is one point of the temperature, while T̅ is the average of the temperature.
a 2
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