Solubilities of Phosphoramidic Acid, N-(phenylmethyl)-, Diphenyl Ester in Selected Solvents

Article abstract of DOI:10.1021/acs.jced.5b00007

Phosphoramidic acid, N-(phenylmethyl)-, diphenyl ester (PANDE) was synthesized, and its thermostability was measured by thermogravimetric analysis. The melting temperature and the fusion enthalpy of PANDE were evaluated by a differential scanning calorime

Full text of DOI:10.1021/acs.jced.5b00007

Article
pubs.acs.org/jced
Solubilities of Phosphoramidic Acid, N‑(phenylmethyl)‑, Diphenyl
Ester in Selected Solvents
Lijuan Wang,† Chaojun Du,*,‡ Xiaojie Wang,† Hongyan Zeng,† Jun Yao,† and Baokuan Chen*,†
†College of Chemistry and Pharmaceutical Engineering, Nanyang Normal University, Nanyang 473061, People’s Republic of China
‡School of Biochemical and Chemical Engineering, Nanyang Institute of Technology, Nanyang 473000, People’s Republic of China
S
* Supporting Information
ABSTRACT: Phosphoramidic acid, N-(phenylmethyl)-, di-
phenyl ester (PANDE) was synthesized, and its thermo-
stability was measured by thermogravimetric analysis. The
melting temperature and the fusion enthalpy of PANDE were
evaluated by a differential scanning calorimeter. The
solubilities of PANDE in chloroform, tertrahydrofuran,
dichloromethane, acetone, methyl acetate, ethyl acetate,
acetonitrile, methanol, and toluene were measured by a
gravimetric method at different temperatures. The solubilities
of PANDE in different solvents at low temperatures are in the
order of chloroform > tetrahydrofuran > dichloromethane > acetone > methyl acetate > ethyl acetate > acetonitrile > methanol >
toluene. At higher temperatures the order is the same except that acetonitrile now becomes the least soluble. The solubility data
of PANDE in nine selected solvents were well fitted by the Wilson, nonrandom two-liquid (NRTL), and universal quasichemical
equations. The Wilson model and the NRTL model show better agreement in general. Finally, the solubility parameters of
PANDE were evaluated by the Scatchard−Hildebrand model, and meanwhile, the standard dissolution enthalpy, the standard
dissolution entropy, and the standard molar Gibbs energy of PANDE in the selected solvents were also calculated by the van’t
Hoff model and the Gibbs−Helmholtz equation. The results show that the dissolution process is endothermic and entropy-
driven.
PANDE have greatly affected its thermal stability, which limites
its applications as a flame retardant in some polymers. When it
is used as a medicine, the impurities may limit its clinical
application and even lead to some side effects. Thus, the
purification process employed to obtain PANDE with high
purity is very significant.
INTRODUCTION
■
Phosphoramidic acid, N-(phenylmethyl)-, diphenyl ester
(PANDE, C19H18NO3P, CAS Registry No. 33985-75-0) is a
white crystalline powder, which was first prepared by Kucherov
in 1949.1 The chemical structure of PANDE is shown in Figure
1. Since the anthelmintic and anticoccidial activity of PANDE
It is well-known that solution crystallization is the key step to
separation and purification for a compound because it
influences purity, crystal habit, yield, crystal size, etc.6
Thermodynamic calculations for a compound are crucial to
designing and controlling its crystallization process.7,8 More-
over, they can also supply the database to evaluate the
applications and limitations of the solution models established
for describing the thermodynamic properties.9 Therefore,
knowledge of (solid + liquid) equilibrium of PANDE in
organic solvents is a necessary procedure when crystallization
isolation processes are designed. Unfortunately, the solubility
data of PANDE have been unavailable up to now.
Figure 1. Structure of phosphoramidic acid, N-(phenylmethyl)-,
diphenyl ester (PANDE).
In this study, PANDE was synthesized and characterized. To
obtain more systematic thermodynamic information on the
crystallization of PANDE from some organic solvents, the
solubility of PANDE was carried out in nine selected solvents,
was discovered in 1980, PANDE has been widely used as a
highly effective agent against Eimeria tenella and Hymelonepsis
nana and so on.2,3 In addition to its biological activity, PANDE
is drawing wide interest due to its perfect flame retardancy to
polycarbonate resin and polyurethane foams with the
advantages of low volatility and low evolution of toxic gases
and smoke in the event of fire.4,5 However, some impurities in
Received: January 3, 2015
Accepted: May 20, 2015
Published: June 1, 2015
© 2015 American Chemical Society
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chloroform, tetrahydrofuran, dichloromethane, acetone, methyl
acetate, ethyl acetate, acetonitrile, methanol, and toluene at
different temperatures at atmospheric pressure by the static
equilibrium method. The experimental data were correlated
with the Scatchard−Hildebrand,10 Wilson,11 nonrandom two-
liquid (NRTL),12 and Universal Quasichemical UNIQUAC13
relations. The experimental solubility and model parameters
used to compare and discuss the solubility were also studied.
Finally, the activity coefficients of PANDE, the dissolution
enthalpies, and entropies of solutions were estimated to better
understand its solubility behavior.
Co., Shanghai), with an uncertainty of 0.01 mg) was used to
weigh the samples.
Synthesis and Characterization. PANDE was prepared
by a slightly modified method from the literature.14 Briefly, 0.5
mol of benzylamine and 0.55 mol of triethylamine mixed with
200 mL dry chloroform were taken into a three necked flask. A
dry chloroformic solution of (C6H5O)2P(O)Cl was dropwise
added into the stirred solution over a period of 1 h. The
temperature of the reaction mixture was kept at 273 K during
the addition of (C6H5O)2P(O)Cl. After the addition of
(C6H5O)2P(O)Cl was completed the reaction mixture was
warmed up to room temperature and left overnight with
stirring. The solvent was removed at a reduced pressure. After
being washed with cold distilled water, the residual material was
recrystallized from acetone and a white crystalline solid
PANDE was obtained. Its mass fraction purity was greater
than 99.0 %, determined by high-performance liquid
chromatography (HPLC; type Shimadzu LC-10AT, Japan).
The EI mass spectrum of PANDE can be seen in Supporting
Information, Figure S1. The intensity (%) m/z is 340.2 (M+).
In Supporting Information, Figure S2, the infrared spectrum of
PANDE contains characteristic absorptions at 3168.6 cm−1 for
N−H stretching, 3053.5 and 3053.5 cm−1 for aromatic −C
C−H stretching, 2937.8 cm−1 for −HC−H stretching; 1590.1,
1487.5, and 1454.6 cm−1 for the phenyl nucleus stretching,
1191.0 cm−1 for the PO stretching, and 1109.6 cm−1 for the
EXPERIMENTAL SECTION
■
Materials. Diphenylchlorophosphate, triethylamine, and
benzylamine were kindly supplied by Zhangjiagang Xinyi
Chemical Co. (Zhangjiagang) and purified by distillation
before using. The solvents used in this work were bought
from Beijing Chemical Factory (Beijing). Adipic acid was
bought from Sigma−Aldrich (USA) with a minimum mass
fraction purity of 0.99, which was determined by high-
performance liquid chromatography (HPLC; type Shimadzu
LC-10AT, Japan). Water used in the experiments was distilled
water.
Apparatus and Procedure. IR spectra (Fourier transform
infrared (FTIR)) was performed on a Nicolet 6700 Fourier-
transform spectrometer (USA) using potassium bromide disks.
1H NMR and 13C NMR spectra were recorded on a Bruker
ARX-400 (Switzerland). Mass spectra were determined by a
LCQ ADVANTAGE MAX (USA). The melting point (Tm)
and the enthalpy of fusion (ΔfusH) were obtained by the
differential scanning calorimeter (DSC type 6200, PerkinElmer
Co., USA) in flowing nitrogen at a heating rate of 10 K·min−1.
1
P−N stretching. The H NMR (CDCl3) spectrum of PANDE
is shown in Supporting Information, Figure S3. The peaks
between 3.79 and 3.98 ppm correspond to the protons of
−NH. The peak at 4.11 ppm corresponds to the protons of
−CH2. The peaks between 6.43 and 7.59 ppm are due to
protons in benzene rings. Supporting Information, Figure S4
presents the 13C NMR (400 Hz, CDCl3) spectrum of PANDE.
In the spectrum, the chemical shifts of carbons with different
chemical environment in the PNBE structure are 150.68,
138.72, 129.53, 128.37, 127.26, 124.76, 120.16, 120.11 and
45.46, respectively.
The calorimetric uncertainty was
1 %, and the measured
uncertainty of the melting point is 0.1 K. Thermogravimetric
analysis (TGA) was carried out with an SDT Q600 (TA
Instruments, USA) thermogravimetric analyzer at a heating rate
of 10 K·min−1 under nitrogen atmosphere.
The experimental setup illustrated in Figure 2 for the
solubility measurements consists of a 120 mL jacketed vessel
with a magnetic stirrer and a circulating water bath used to
maintain the temperature within 0.01 K. A condenser was
used to prevent the evaporation of the solvent. An analytical
balance (type TG328B, Shanghai Balance Instrument Works
Solubility Measurement. The solubilities of PANDE in
the solvents at different temperatures were determined by the
dissolution method.15 A 50 mL sample of solvent and an excess
amount of PANDE were added into the jacketed vessel of 120
mL. The solution was stirred for 5 h to ensure equilibrium was
reached. The equilibrium was confirmed by repeated
concentration analyses at an interval of 30 min. It was found
that 5 h was long enough to establish the solid−liquid
equilibrium in the equilibrium cell. After equilibrium was
reached, the stirring was stopped to let the particles settle
down. A preheated syringe was used to take approximatly 2 mL
of the clear upper saturated solution out. The solution was
quickly transferred into a 5 mL beaker with a cover to prevent
the loss of solvent. The mass was determined immediately by
the analytical balance. And then the beaker was put into a
vacuum dryer oven at T = 328 K for 3 days to evaporate all the
solvent. The mass of the sample was recorded repeatedly
throughout the drying process and it was found that there is no
PANDE loss after drying for 3 days in vacuum. The mass was
obtained after the solvents were completely evaporated. During
the experiments, each experiment was recorded in triplicate.
FTIR was used to analyze the samples to ensure that no
thermal decomposition effect had occurred with the PANDE
and no solvate material was generated during the experiments.
The mole fraction, x1, was calculated by the following equation:
Figure 2. Schematic diagram of the experimental apparatus: 1,
thermostatic water-circulator bath; 2, sampling port; 3, jacketed glass
vessel; 4, magnetic stirrer; 5, magnetic agitator drive; 6, thermometer;
7, condenser.
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w1/M1
x1 =
w1/M1 + w2/M2
(1)
where w1, w2, M1 and M2 are the mass of the solute and solvent,
molar mass of the solute and solvent, respectively. The average
value was obtained from the three experiments at each
temperature. The uncertainty of the experiment measurement
was about 2%.
To validate the accuracy of the solubility data measured by
the experimental apparatus, the solubilities of adipic acid in
water and ethanol was determined (Figure 3 and Supporting
Figure 5. TGA thermograms of PANDE under N2.
Table 1. Solubility Parameter and Molar Volume of the
Selected Solvents and PANDE
δi
106Vi
1/2
solvent
methanol
(J·cm−3
)
m3·mol−1
r
q
29.52
20.38
24.09
18.35
19.13
19.03
40.70
64.43
52.68
98.59
81.94
80.66
81.50
106.6
73.93
275.40
1.4311
2.2564
1.8701
3.4786
2.9415
2.8700
2.8042
3.9228
2.5735
12.203
1.432
1.988
1.724
3.116
2.720
2.410
2.576
2.968
2.336
9.058
dichloromethane
acetonitrile
ethyl acetate
tetrahydrofuran
chloroform
methyl acetate
toluene
Figure 3. Comparison of the literature and experimental mole fraction
of adipic acid solubility (x) against temperature in water and ethanol:
16
17
■
□
△
17
○
, water (this work); , ethanol (this work);
, water;
, water;
19.435
18.35
19.77
23.55
●
, ethanol.
acetone
Information, Table S1). It can be seen that the solubilities
achieved in this work are in good agreement with literature.16,17
Thus, the reliability and the repeatability of our experimental
apparatus were verified.
PANDE
solvents including the molar volume V, solubility parameter
δ, volume fraction r, and area fraction q are gathered from the
literature18,19 and are listed in Table 1. The properties of
PANDE, as evaluated by using advanced chemistry develop-
ment (ACD/Laboratories) Software v11.02 are also listed in
Table 1.
RESULTS AND DISCUSSION
■
Evaluation of Pure Component Properties. The DSC
results in Figure 4 show that the melting point and the enthalpy
Solubility Data of PANDE. The solubility data of PANDE
in the selected solvents at different temperatures are presented
in Table 2, and the plot of the solubility data of PANDE in the
solvents at different temperatures is shown in Figure 6. The
solubility of PANDE increases with an increase of temperature.
The solubilities of PANDE are high in chloroform, tetrahy-
drofuran, and dichloromethane, and low in methanol and
toluene. Furthermore, the solubilities in methanol and
dichloromethane vary more with temperature than the other
solvents. This may be helpful for the recrystallization of
PANDE. The solubilities of PANDE in different solvents at low
temperature are in the order of chloroform > tetrahydrofuran >
dichloromethane > acetone > methyl acetate > ethyl acetate >
acetonitrile > methanol > toluene. At higher temperatures the
order is the same except acetonitrile now becomes the least
soluble. Unexpectedly, the dissolution properties of the
PANDE in the selected solvents are not consistent with the
polarity order of the solvents [polarity: methanol (76.2) >
acetonitrile (46) > acetone (35.5) > dichloromethane (30.9) >
methyl acetate (29) > chloroform (25.9) > ethyl acetate (23) >
tetrahydrofuran (21) > benzene (11.1) > toluene (9.9)].20 The
solubility behaviors are affected not only by the polarities of the
Figure 4. Experimental heat Q flow from DSC measurement of
PANDE.
of fusion for PANDE are 381.1 0.1 K and 106.6 0.7 J·g−1,
respectively. The TGA results in Figure 5 show that there is a
major one step decomposition and only about 4.7 % char
residue remains. The physical properties of the selected
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Table 2. Mole Fraction Solubilities (x) and Activity Coefficients (γ) of PANDE in the Selected Solvents at Temperature T and
a
Pressure p = 0.1 MPa
solvent
methanol
T/K
102x
γ
solvent
T/K
102x
γ
293.15
298.15
303.15
308.15
313.15
318.15
323.15
328.15
333.15
293.15
298.15
303.15
308.15
313.15
318.15
323.15
293.15
298.15
303.15
308.15
313.15
318.15
323.15
293.15
298.15
303.15
308.15
313.15
318.15
323.15
328.15
333.15
288.15
293.15
298.15
303.15
308.15
313.15
318.15
1.112
1.576
2.915
2.638
2.293
2.070
1.863
1.653
1.469
1.259
1.157
0.726
0.708
0.713
0.677
0.684
0.674
0.648
0.331
0.361
0.401
0.425
0.458
0.499
0.537
1.630
1.492
1.436
1.378
1.334
1.263
1.232
1.152
1.060
0.264
0.299
0.329
0.371
0.406
0.439
0.477
323.15
328.15
288.15
293.15
298.15
303.15
308.15
288.15
293.15
298.15
303.15
308.15
313.15
318.15
323.15
293.15
298.15
303.15
308.15
313.15
318.15
323.15
328.15
333.15
338.15
343.15
293.15
298.15
303.15
308.15
313.15
318.15
323.15
328.15
333.15
338.15
24.757
27.526
5.501
7.239
9.652
12.551
15.709
1.682
2.338
3.088
4.070
5.502
6.990
9.402
12.217
1.086
1.604
2.277
3.122
4.278
5.741
8.142
10.822
14.637
18.715
24.296
1.477
1.964
2.640
3.444
4.308
5.909
7.422
9.477
12.174
15.484
0.519
0.573
0.455
0.448
0.431
0.421
0.425
1.490
1.387
1.346
1.299
1.213
1.196
1.106
1.052
2.986
2.592
2.323
2.138
1.955
1.812
1.578
1.458
1.315
1.248
1.159
2.194
2.117
2.003
1.938
1.941
1.760
1.731
1.665
1.581
1.508
2.306
dichloromethan
3.224
4.488
6.292
8.751
12.532
16.642
4.467
methyl acetate
acetone
5.869
7.412
9.857
12.221
15.434
19.830
9.780
toluene
tetrahydrofuran
11.528
13.202
15.703
18.269
20.830
23.954
1.989
ethyl acetate
2.786
3.684
4.842
acetonitrile
6.266
8.235
10.433
13.690
18.152
9.503
chloroform
10.859
12.630
14.271
16.428
19.052
21.810
a
Standard uncertainties u are u(T) = 0.01 K, u(x) = 0.002, u(γ) =
0.002.
⎛
⎜
⎞
⎛
⎜
⎝
⎞
⎟
⎠
solvents but also by the intermolecular interaction, and the
ability to form a hydrogen bond between the solvent and
PANDE.21 The solubility values in tetrahydrofuran and acetone
are greater than those in the methanol, which indicates the
property of the proton donor of the NH group in PANDE.
Meanwhile, the value in methanol is greater than that in toluene
at high temperature, which may be the reason for hydrogen
bonds between methanol and PANDE molecules. The high
solubility value in chloroform and dichloromethane might be
related to the strong electronegativity of elemental chlorine.
From the solubility data, tetrahydrofuran, acetone, chloroform,
and dichloromethane are suggested as the solvents for the
crystallization of PANDE. The four solvents are also suggested
as the potential reaction solvents.
ΔHfus
RTm
ΔHtr
T
T
Tm
T
1
x1γ
tr
⎟
ln
=
− 1 +
− 1
⎝
⎠
RT
tr
1
⎛
⎞
ΔCp
Tm
T
−
ln
+
− 1
⎜
⎟
R
Tm
T
⎝
⎠
(2)
where T, ΔHtr, Ttr, ΔCp, γ1, and R denote the equilibrium
temperature, enthalpy of solid−solid phase transition of the
solute, temperature of phase transition, heat capacity of the
solute at its melting point, the activity coefficient of the solute
and the gas constant, respectively. There is no transition in the
PANDE solid phase and the contributions of the heat capacities
are neglected. Thus, a simplified form of the equation above
can be derived as a fair approximation.23
⎛
⎞
ΔHfus
R
1
1
T
Solid−liquid phase equilibrium of PANDE in the pure
ln x1 =
−
− ln γ
1
⎜
⎝
⎟
⎠
solvents can be written in a very general manner as follows:22
T
(3)
m
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⎛
⎞
Λ12
Λ21
x2 + Λ21x1
ln γ = −ln(x + Λ x ) + x
−
⎜
⎝
⎟
⎠
1
12
2
2
1
x + Λ x
1
12 2
(4)
⎛
⎞
⎟
⎠
⎛
⎞
⎟
⎠
v2
v1
λ12 − λ11
v2
v1
Δλ12
RT
⎜
⎜
Λ12
Λ21
=
=
exp −
=
exp −
⎝
⎛
⎝
RT
(5)
⎞
⎟
⎠
⎛
⎞
⎟
⎠
v1
v2
λ21 − λ22
v1
v2
Δλ21
⎜
⎜
exp −
=
exp −
⎝
⎝
RT
RT
(6)
Here, Δλ11, Δλ12, v1, v2 refer the cross interaction energy
parameters, the molar volumes of solute, and the molar
volumes of solvent, respectively.
NRTL Model. The activity coefficient of the NRTL model12
is expressed as
2
⎡
⎤
⎥
⎦
⎛
⎞
G21
τ12G12
2
⎢
⎥
ln γ = x2 τ21
+
⎜
⎟
⎠
1
Figure 6. Mole fraction solubility data of PANDE in selected solvents:
⎢
x + x G
⎝
(x2 + x1G12)2
1
2 21
⎣
(7)
(8)
●
▲
▽
☆, chloroform; , tertrahydrofuran; , dichloromethane; , acetone;
□
■
○
▼
△
, methyl acetate; , ethyl acetate; , acetonitrile; , methanol; ,
Gij = exp(−aijτij)
gij − gjj
toluene.
Δgij
Table 3. van der Waals Group Volume and Surface Area
Parameters for the UNIQUAC Model17,18
τ =
=
ij
(9)
RT
RT
group
R
Q
where, τ12, τ21, G12, and G21 are model parameters; a, Δg12, and
Δg21 denote the parameters indicating the nonrandomness in
the mixture and the cross interaction energy parameters (J·
mol−1), respectively. In this study, a is selected as 0.3.
UNIQUAC Model. The UNIQUAC model13 for the
calculation of the activity coefficient of PANDE in the pure
solvents is
(O−)(−O)P(O)−
1.9312
0.5313
0.3652
1.2070
1.762
0.400
0.120
0.936
ACH
AC
-CH2NH-
ln γ = ln γC + ln γ R
(10)
1
1
1
On the basis of the values of x1, Tm, and ΔHfus, the activity
coefficients of PANDE in solid−liquid equilibrium can be
obtained from eq 3, and the results are also shown in Table 1.
The solute activity coefficients in a saturated solution decided
by temperature can estimate the PANDE−solvent intermo-
lecular interactions. From Table 1, the values of γI < 1 in
tetrahydrofuran, acetone, chloroform, and dichloromethane
indicate that the solutions deviate positively from Raoult’s law,
while the other systems exhibit negative deviations. The main
reason may be related to the complicated hydrogen bond in the
systems.
⎛
⎝
⎞
⎠
⎛
⎞
⎛
⎞
ϕ1
r
r2
z
2
θ
ln γC = ln
+
q ln
+ φ l − 1 l
⎜
⎟
⎟
⎜
⎟
⎠
⎜
⎟
⎠
⎜
1
2
1
2
1
x
ϕ
⎝
⎝
1
(11)
1
ln γ R = −q ln(θ1 + θ2τ21)
1
1
⎛
⎞
τ21
θ + θ τ
τ12
+ θ q
−
⎜
⎟
⎠
2
1
θ2 + θ1τ12
⎝
(12)
(13)
1
2 21
z
2
l1 = (r − q ) − (r − 1)
1
1
1
Correlation of Solubility Data. Wilson Model. Wilson’s
model11 for the calculation of the activity coefficient of PANDE
in the pure solvent is
z
2
l2 = (r2 − q2) − (r2 − 1)
Table 4. Regressed Parameters and RSDs for the Wilson Equation11
α12
β12
α21
β21
solvent
methanol
J/mol
J/(mol·K)
J/mol
J/(mol·K)
RSD %
5215.22
−2307.49
−11351.4
−130385
−7145.82
−78398.9
−6168.77
−9393.39
29776.1
−11.4298
23.4968
45.0530
484.657
22.3561
303.090
20.5877
29.3502
−94.7739
2839.30
6132.62
−5.55683
−29.5983
−191.170
4.15517
1.10
1.80
1.30
0.80
1.50
0.83
1.00
0.65
0.35
1.00
acetone
acetonitrile
tetrahydrofuran
ethyl acetate
chloroform
methyl acetate
toluene
117151
−9427.42
8298.82
−1.40802
9.15763
−11167.7
7096.52
−0.772797
−305.594
108.967
108593
dichloromethane
overall
−35742.1
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Table 5. Regressed Parameters and RSDs for the NRTL Model12
α12
β12
α21
β21
solvent
methanol
J/mol
J/(mol·K)
J/mol
J/(mol·K)
RSD %
11698.9
−15.7167
−15.6159
50.3187
62.3176
2.37831
49.3871
−20.6706
−40.1779
100.000
−244.054
28495.9
−9.26559
−73.7959
56.8344
0.98
1.32
1.53
0.36
1.62
0.62
1.12
1.41
0.61
1.10
acetone
737.679
acetonitrile
tetrahydrofuran
ethyl acetate
chloroform
methyl acetate
toluene
−24939.6
−1930.36
4656.37
2547.60
13343.0
16459.2
−29837.2
−16823.4
−16867.0
−768.043
−15841.0
−4798.70
−2418.94
31282.8
38.1956
−7.11223
34.9107
3.35018
2.80514
dichloromethane
overall
−111.886
Table 6. Regressed Parameters and RSDs for the UNIQUAC Model13
α12
β12
α21
β21
solvent
methanol
J/mol
J/(mol·K)
J/mol
J/(mol·K)
RSD %
−336.662
1834.74
2318.29
−1142.36
2714.30
785.406
326.570
571.273
1357.93
2736.02
−1851.67
−7978.76
3247.68
−9503.74
2996.20
154.784
3146.58
996.073
516.449
−170.588
3476.72
−2856.66
2210.88
1.89
4.00
2.66
3.29
1.73
3.37
1.18
3.92
5.90
2.79
acetone
acetonitrile
tetrahydrofuran
ethyl acetate
chloroform
methyl acetate
toluene
−758.680
−973.629
−52.3743
−710.013
−386.880
−317.599
4197.75
365.084
−361.612
−3.69526
−2051.02
−0.357729
−4333.73
dichloromethane
overall
Table 7. Caculated Values for Dissolution Enthalpy and
Dissolution Entropy of PANDE in Different Pure Solvents
ΔH0d
ΔS0d
solvent
methanol
J/mol
J/mol·K
55177.44
38856.98
23614.75
43952.79
21260.64
39118.45
51925.67
43497.60
42922.85
150.60
106.69
61.200
117.45
54.090
111.67
139.69
117.00
111.28
acetone
tetrahydrofuran
ethyl acetate
chloroform
dichloromethane
toluene
methyl acetate
acetonitrile
Table 3, and used to calculate the parameters of r and q for
PANDE.
Figure 7. Function Y for PANDE versus solvent solubility parameters
δ2. Regression line: y = −47.09δ2 + 536.41 (R2 = 0.9964).
As used in the literature,24 the binary cross-interaction
parameters in the three models mentioned above were assumed
to have a linear dependency on temperature as eq 16.
⎛
⎞
⎟
⎠
⎛
u12 − u22
⎞
⎟
Δu12
RT
⎜
⎜
τ12 = exp −
= exp −
⎝
⎛
⎠
⎝
⎛
RT
(14)
kij = αij + β T
ij
(16)
⎞
⎟
⎠
u21 − u11 ⎞
Δu21
RT
⎜
⎟
⎜
τ21 = exp −
= exp −
In which α, β, and k represent the parameters used to fit the
solubility data and the interaction parameter, respectively.
The parameters of the Wilson model, NRTL model, and
UNIQUAC model were obtained by the regression of the
experimental solubility data and are listed respectively in Tables
4, 5, and 6 together with relative standard deviations (RSDs)
used to identify the difference between the measured and
calculated data, which was defined by eq 17.
⎝
⎠
⎝
RT
(15)
where Φ, r, q, θ, Δu12(Δu21), and z are the UNIQUAC
molecular surface fraction, the UNIQUAC volume parameter,
the UNIQUAC surface parameter, the volume fraction,
adjustable energy parameters, and the coordination number,
respectively. The van der Waals group volume (R) and surface
area (Q) parameters collected from the literature18 are listed in
1819
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Table 8. Standard Molar Gibbs Energy ΔG0d and of PANDE in the 10 Selected Solvents at Different Temperature Together with
%ζH and %ζTS
T
ΔG0d
T
ΔG0d
solvent
methanol
K
J/mol
%ζH
%ζTS
solvent
K
J/mol
%ζH
%ζTS
293.15
298.15
303.15
308.15
313.15
318.15
323.15
328.15
333.15
293.15
298.15
303.15
308.15
313.15
318.15
323.15
293.15
298.15
303.15
308.15
313.15
318.15
323.15
293.15
298.15
303.15
308.15
313.15
318.15
323.15
328.15
333.15
288.15
293.15
298.15
303.15
308.15
313.15
11029.1
10276.1
9523.05
8770.05
8017.05
7264.05
6511.05
5758.05
5005.05
7580.81
7047.36
6513.91
5980.46
5447.01
4913.56
4380.11
5673.97
5367.97
5061.97
4755.97
4449.97
4143.97
3837.97
9522.32
8935.07
8347.82
7760.57
7173.32
6586.07
5998.82
5411.57
4824.32
5674.61
5404.16
5133.71
4863.26
4592.81
4322.36
55.55
55.13
54.72
54.32
53.92
53.52
53.14
52.75
52.38
55.40
54.99
54.57
54.17
53.77
53.37
52.99
56.83
56.41
56.00
55.60
55.20
54.81
54.42
56.07
55.66
55.25
54.84
54.44
54.05
53.66
53.28
52.90
57.70
57.28
56.87
56.46
56.05
55.66
44.45
44.87
45.28
45.68
46.08
46.48
46.86
47.25
47.62
44.60
45.01
45.43
45.83
46.23
46.63
47.01
43.17
43.59
44.00
44.40
44.80
45.19
45.58
43.93
44.34
44.75
45.16
45.56
45.95
46.34
46.72
47.10
42.30
42.72
43.13
43.54
43.95
44.34
318.15
323.15
328.15
288.15
293.15
298.15
303.15
308.15
288.15
293.15
298.15
303.15
308.15
313.15
318.15
323.15
293.15
298.15
303.15
308.15
313.15
318.15
323.15
328.15
333.15
338.15
343.15
293.15
298.15
303.15
308.15
313.15
318.15
323.15
328.15
333.15
338.15
4051.91
3781.46
3511.01
6940.74
6382.39
5824.04
5265.69
4707.34
9784.05
9199.05
8614.05
8029.05
7444.05
6859.05
6274.05
5689.05
10975.6
10277.1
9578.65
8880.20
8181.75
7483.30
6784.85
6086.40
5387.95
4689.50
3991.05
10301.1
9744.72
9188.32
8631.92
8075.52
7519.12
6962.72
6406.32
5849.92
5293.52
55.27
54.88
54.50
54.87
54.44
54.021
53.61
53.20
56.34
55.91
55.49
55.08
54.68
54.28
53.89
53.50
55.91
55.49
55.08
54.68
54.28
53.88
53.49
53.11
52.74
52.36
52.00
56.82
56.40
55.99
55.59
55.19
54.80
54.41
54.03
53.66
53.29
44.73
45.12
45.50
45.13
45.56
45.98
46.39
46.80
43.66
44.09
44.51
44.92
45.32
45.72
46.11
46.50
44.091
44.51
44.92
45.32
45.72
46.12
46.51
46.89
47.26
47.64
48.00
43.18
43.60
44.01
44.41
44.81
45.20
45.59
45.97
46.34
46.71
dichloromethane
methyl acetate
acetone
tetrahydrofuran
toluene
ethyl acetate
acetonitrile
chloroform
1/2
activity coefficient of PANDE in the pure solvent is expressed
as
2
⎡
⎤
γ − γcalcd
N
⎛
⎝
⎞
⎠
1
N
⎢
i
i
⎥
⎜
⎜
⎟
⎟
RSD =
∑
⎢
⎥
γ
2
RT ln γ = Vϕ (δ1 − δ2)2
i
i=1
⎣
⎦
(17)
(18)
1
1
2
x2V
Here, N is the total number of data points for each system.
It can be seen that all RSDs of the Wilson model and NRTL
model from Tables 4 and 5 are less than 1.80 % and 1.62 %,
respectively, and the UNIQUAC model is better in fitting the
measured solubility data of PANDE in methanol (1.89 %),
ethyl acetate (1.73 %) and methyl acetate (1.18 %) than for the
other selected solvents. The overall deviations of the Wilson
model (1.00 %) and the NRTL model (1.10 %) are smaller
than that of the UNIQUAC model (2.79 %), so the Wilson
model and the NRTL model can give the better description for
the solubility data.
2
ϕ2 =
x2V + x1V1
(19)
2
where, V1, δ1, δ2, and ϕ2 are the molar volume of the subcooled
liquid of pure solid solute, the solubility parameters of the
solute and solvent, and the volume fraction of solvent in the
binary mixture, respectively.
The Scatchard−Hildebrand model, can be rewritten as eq 20
RT ln γ
1
2
2
Y =
− δ2 = −2δ1δ2 + δ1
2
Vϕ
(20)
1
2
From eq 20, the solubility parameter δ1 of PANDE can be
calculated from the slope of the line formed between Y and the
solvent solubility parameter δ2 for the specified solute and
Calculation of Solubility Parameter of PANDE. The
Scatchard−Hildebrand model10 for the calculation of the
1820
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Article
temperature. The results obtained for PANDE at 293.15 K are
plotted in Figure 7. The estimated solubility parameter δ1 for
PANDE is 23.55 0.05 (J·cm−3)0.5 and is also listed in Table 1.
Dissolution Properties. The standard molar dissolution
enthalpy and the standard molar dissolution entropy of
PANDE in the different solvents at saturation (ΔH0d and
ΔS0d) can be calculated by the van’t Hoff equation, while the
standard molar Gibbs energy ΔGd0 at saturation can be
calculated by the Gibbs−Helmholtz equation.24
NRTL model show slightly better agreement. The overall RSDs
show that the Wilson model gives the best agreement between
the experimental data and calculated data for the three models.
The solubility parameter of PANDE was caculated by the
Scatchard−Hildebrand model. On the basis of the van’t Hoff
equation and the Gibbs−Helmholtz equation, the dissolution
enthalpy and entropy, and the standard molar Gibbs energy of
PANDE are calculated in different solvents. These data
presented in this work could be used for the separation and
purification process of PANDE to get high quality products.
ΔHd0
ΔSd0
R
ln x1 = −
+
(21)
(22)
RT
ASSOCIATED CONTENT
■
S
* Supporting Information
ΔGd0 = ΔHd0 − TΔSd0
1
IR, H NMR, 13C NMR, MS spectra of PANDE and the
The results of the standard molar dissolution enthalpy ΔHd0
and the standard molar dissolution entropy ΔS0d are presented
in Table 7, and the standard molar Gibbs energy is listed in
Table 8. The calculated values show that within the
experimental temperature range, the dissolving process of
PANDE is endothermic (ΔHd0 > 0). The higher the values of
the enthalpy are, the more powerful the cohesive forces
between PANDE and the selected solvent are. Meanwhile, the
high values of the enthalpy demonstrate a strong temperature
dependence on solubility.25,26 The positive values of the
standard molar Gibbs energy for all cases in Table 8 suggest
that the process is nonspontaneous. While the positive values of
the standard molar entropy presented in Table 4 provide an
indication that the entropy is the driving force for the solution
process.
standard molar Gibbs energy of PANDE. The Supporting
Information is available free of charge on the ACS Publications
website at DOI: 10.1021/acs.jced.5b00007.
AUTHOR INFORMATION
Corresponding Authors
*E-mail: chenbaokuan@163.com.
*E-mail: hyperchem@126.com.
■
Funding
Financial support from Henan Province Project Education
Fund (14A150020), Henan Province Project Education Fund
(14A150032), Natural Science Foundation of Nanyang Normal
University (ZX2014038), and Natural Science Foundation of
Nanyang Normal University (ZX2014045) are acknowledged.
According to the literature,27,28 %ζH and %ζTS defined by eq
23 and eq 24 compare the relative contribution of enthalpy and
entropy in the solution process to the standard Gibbs energy.
Notes
The authors declare no competing financial interest.
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CONCLUSIONS
■
The solubilities of PANDE in chloroform, tertrahydrofuran,
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gravimetric method at different temperatures. The solubilities
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