Solid-Liquid Phase Equilibrium of Phosphoramidic acid, N,N′-1,2-Ethanediylbis-P,P,P′,P′-tetraphenyl Ester in Selected Solvents

Article abstract of DOI:10.1021/je5010565

Phosphoramidic acid, N,N′-1,2-ethanediylbis-P,P,P′,P′-tetraphenyl ester (PAETE) was prepared and characterized by elemental analysis (EA), mass spectra (MS), infrared spectroscopy (IR), and nuclear magnetic resonance (NMR). The thermostability of PAETE wa

Full text of DOI:10.1021/je5010565

Article
pubs.acs.org/jced
Solid−Liquid Phase Equilibrium of Phosphoramidic acid, N,N′‑1,2-
Ethanediylbis‑P,P,P′,P′‑tetraphenyl Ester in Selected Solvents
Baokuan Chen,† Chaojun Du,‡ Hui Zhou,† Jingjing Wang,† and Lijuan Wang*,†
†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,N′-1,2-ethanediylbis-
P,P,P′,P′-tetraphenyl ester (PAETE) was prepared and
characterized by elemental analysis (EA), mass spectra (MS),
infrared spectroscopy (IR), and nuclear magnetic resonance
(NMR). The thermostability of PAETE was measured via
thermogravimetric analysis (TGA). The melting temperature
and the fusion enthalpy of PAETE were evaluated by differential
scanning calorimeter (DSC). The solubilities of PAETE in ten
selected solvents were obtained using a gravimetric method.
The experimental data were well correlated by the Buchowski−Ksiazczak (λh), Scatchard−Hildebrand, modified Apelblat model,
and the ideal equations. The solubility parameter of PAETE was estimated by the Scatchard−Hildebrand Model. The dissolution
enthalpy and entropy of PAETE in the ten selected solvents were also calculated by the modified Apelblat model.
■. INTRODUCTION
The high-level living standard would not be possible without
the development of polymeric materials that have appeared
since World War II.1 Nowadays, polymers have been widely
used in various fields, such as aerospace, mechanics, and
chemistry, due to the good heat endurance and mechanical
performance, small chemical corrosion resistance, and so on.2
Figure 1. Structure of the phosphoramidic acid, N,N′-1,2-ethanediyl-
bis-P,P,P′,P′-tetraphenyl ester (PAETE).
Unfortunately, almost all of the polymers are easily to burn,
which limits their applications in electronics, transportation,
cabling, construction, and so on. Flame retardancy is
mandatorily required in the fields mentioned above.3 To
However, some impurities have greatly effects on its thermal
property and the application. Hence, purifying PAETE is
important to gain the product with high purity.
decrease the fire hazards and expand the range of the
applications for the polymer materials, it is urgent to develop
the flame retardant polymer materials. It is well know that
adding the flame retardant additives into the polymer materials
is an effective method to enhance the flame retardancy.
Recently, some reports indicate that the flame retardant
efficiency can be greatly enhanced while nitrogen and
phosphorus elements are present together in the polymer
systems. The synergism of phosphorus and nitrogen elements
has been recognized in many research works.4−7 Now, it is
predicted that the phosphorus−nitrogen-based flame retardants
will be the biggest growing share in the flame retardant market.8
Phosphoramidic acid, N,N′-1,2-ethanediylbis-P,P,P′,P′-tetra-
phenyl ester (PAETE) (C26H26N2O6P2, CAS Registry No.
34670-52-5) has gained increasing attention over the past years
as a versatile intumescent flame retardant because the
phosphorus and nitrogen elements present in the formula.
Figure 1 shows the chemical structure. PAETE possesses a
bright future because of its powerful flame retardancy. It has
been widely used in thermoplastic polyolefin,9 polyethy-
lene,10,11 epoxy resins,12 polycarbonate(PC),13 and so forth.
As the solubility of PAETE in water is very low, knowledge of
(solid + liquid) equilibrium of PAETE in organic solvents is
especially necessary for determining the optimal conditions in
the crystallization isolation processes. Furthermore, it can also
provide the database of evaluating the applications and
limitations for the solution models established for predicting
the thermodynamic properties.14 However, the crystallization
method of separating PAETE and the solubility data of PAETE
have not been reported. In the work, PAETE was synthesized
and characterized. To obtain a high yield and separation
efficiency via selecting the optimal solvent, and achieve more
systematic thermodynamic information on the crystallization
for PAETE from some organic solvents, the solubilities of
PAETE in ten selected organic solvents were measured. The
modified Apelblat equation,15 Ideal model,16 Scatchard−
Received: November 22, 2014
Accepted: May 13, 2015
Published: May 21, 2015
© 2015 American Chemical Society
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Hildebrand,17 and Buchowski−Ksiazczak (λh) model18 were
employed to correlate the solubility data based on the pure
component with the thermophysical properties. Moreover, the
activity coefficients of PAETE, the mixing enthalpies and
entropies of solutions were estimated to understand the
solubility behavior.
■. EXPERIMENTAL SECTION
Materials. Diphenylchlorophosphate was supplied by Xinyi
Chemical Co., Ltd. (Zhangjiagang) and purified by distillation
before using. Triethylamine and ethylenediamine were
purchased from Weisi Chemical Reagents Co. (Beijing). All
the solvents purchased from Beijing Chemical Factory were
analytical grade. The mass fraction purities were all higher than
0.99 (Table 1) and used as received.
Figure 2. Schematic diagram of the experimental apparatus: 1,
thermostatic water-circulator bath; 2, sample gauge; 3, jacketed glass
vessel; 4, magnetic stirrer; 5, magnetic agitator drive; 6, thermometer;
7, condenser.
Table 1. Description of the Solute and Solvents Used in This
Paper
disks. A DSC Q100 (TA Instruments) differential scanning
calorimeter (DSC) was used to determine the melting point
and enthalpy of fusion under N2 atmosphere at a heating rate of
10 K·min−1. The uncertainty of DSC measurement was the
same as that reported in our previous work.22 An Elementar
Vario EL element analyzer was used as the elemental analysis.
1H NMR and 13C NMR spectra were achieved by a Bruker
ARX-400. An SDT Q600 (TA Instruments) thermogravimetric
analyzer was applied as thermogravimetric analysis (TGA) at a
heating rate of 10 K· min−1 in flowing N2.
Synthesis of PAETE. PAETE was synthesized by the same
method reported in our previous work.20 To a dry chloroformic
solution of (C6H5O)2P(O)Cl, a dry chloroformic solution of
ethanediamine and triethylamine (1:1:2.1 molar ratio) was
added, dropwise for 1 h at 273 K. After stirring for 6 h, the
solvent was removed at reduced pressure. Then, the
recrystallization of the residual material was conducted by
washing with cold distilled water from acetone to obtain
PAETE as a white crystalline solid. The mass fraction purity of
PAETE was about 0.99, which was determined by high-
performance liquid chromatography made in Japan (HPLC;
Shimadzu LC-10AT).
mass
fraction
purification
method
chemical name
source
diphenylchlorophosphate Zhangjiagang Xinyi
>0.990
none
Chemical Co.,
Ltd.
triethylamine
chloroform
ethanediamine
ethyl acetate
acetone
Weisi Chemical
Reagents Co., Ltd.
>0.990
>0.995
>0.990
>0.995
>0.995
>0.995
>0.995
>0.998
>0.995
>0.995
>0.995
>0.995
none
Beijing Chemical
Factory
none
Weisi Chemical
Reagents Co., Ltd.
none
Beijing Chemical
Reagents Co., Ltd.
none
Beijing Chemical
Factory
none
ethanol
Beijing Chemical
Factory
none
methanol
Beijing Chemical
Factory
none
tetrahydrofuran
methyl acetate
benzene
Beijing Chemical
Factory
none
Beijing Chemical
Factory
none
Beijing Chemical
Factory
none
Characterization of PAETE. EI mass spectrum of PAETE
is shown in Figure S1 of the Supporting Information. The
intensity (%) m/z of PAETE is 525.2 (M + 1). Elemental
analysis (%, calcd): C, 59.54% (60.37%); H, 5.00% (4.82%); N,
5.34% (5.28%). In Figure S2 of the Supporting Information, the
infrared spectrum of PAETE contains characteristic absorptions
at 3221 cm−1 for NH stretching, 3058 cm−1 for aromatic 
CCH stretching, 2944 and 2885 cm−1 for HCH
stretching, ring carbon−carbon stretching vibrations at 1589,
1489, and 1469 cm−1, 1191 cm−1 for the PO stretching, 1025
cm−1 for the PN stretching, 1250 cm−1 for the CN
stretching and 934 cm−1 for the POaryl stretching. Figure
S3 of the Supporting Information shows the 1H NMR spectrum
toluene
Beijing Chemical
Factory
none
acetonitrile
PAETE
Beijing Chemical
Factory
none
a
as-prepared
>0.990
recrystallization
a
PAETE (Phosphoramidic acid, N,N′-1,2-ethanediylbis-P,P,P′,P′-
tetraphenyl ester) determined by the high-performance liquid
chromatography.
Apparatus and Procedure. The experimental apparatus
used to measure the solubility was similar to that previously
reported.19 Figure 2 presents the setup. A jacketed equilibrium
cell was used to measure the solubility. The cell was with a
working volume (120 mL) and a magnetic stirrer. A circulating
water bath was applied with a thermostat of 50 L, made by
Shanghai Laboratory Instrument Works Co., Ltd. to keep the
temperature within 0.05 K. A condenser was used to prevent
the solvent evaporating. An analytical balance (TG328B), made
by Shanghai Balance Instrument Works Co. with an uncertainty
of 0.1 mg was used for weighing the samples.
1
of PAETE. H NMR (400 MHz, CDCl3) δ 7.56−7.01 (m,
20H), 4.43−4.35 (t, 2H), 3.04−2.99 (m, 4H). Supporting
Information Figure S4 presents 13C NMR (400 Hz, CDCl3)
spectrum of PAETE. The chemical shifts of carbons with
different chemical environments in PAETE structure are 42.95,
120.22, 129.46, 129.74 and 151.71, respectively.
Solubility Measurement. Equilibrium solubility determi-
nations of the PAETE in chloroform, acetone, ethyl acetate,
ethanol, benzene, tetrahydrofuran, methanol, acetonitrile,
methyl acetate, and toluene were performed by the gravimetric
method.21 First, an excess of PAETE was put into a known
Fourier transform infrared (FTIR) spectra were performed in
a Nicolet 6700 Fourier-transform spectrometer in the wave-
number range of 400−4000 cm−1 using potassium bromide
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mass of solvent in the equilibrium cell for each measurement.
Second, the equilibrium cell was heated and stirred at a
constant temperature for 8 h, long enough to achieve solid−
liquid equilibrium in the equilibrium cell. The solution was
settled for 5 h after the stirring was stopped. The clear upper
saturated solution was withdrawn by a preheated injector with a
cotton filter and then quickly transferred into a 5 cm3 beaker
with a cover to prevent solvent losing. The total mass was
determined by the analytical balance immediately. The beaker
must be placed into a vacuum oven at 308 K for 3 days to
evaporate all solvents and then measure its mass. The mass of
the samples was repeatedly weighed throughout the drying
process to make sure no solvent remained. The masses were
recorded when the solvents have completely evaporated.
During the experiments, each experiment was repeated three
times for the solvent with the same composition at each
temperature, and then an average value is given. The mole
fraction, x1, was obtained from the equation as follows:
Figure 4. TGA thermograms of PAETE under N2.
w1/M1
x1 =
acetate, ethanol, benzene, tetrahydrofuran, methanol, acetoni-
trile, methyl acetate, and toluene at different temperature range
are presented in Supporting Informaiton Table S1. On the basis
of the values of x1, Tm, and ΔfusH, the activity coefficients of
PAETE in solid−liquid equilibrium can be obtained by eq 3
and are also shown in Supporting Informaiton Table S1
w1/M1 + w2/M2
(1)
where w1 and w2 are the masses of the solute and solvent,
respectively. M1 and M2 are molar masses of the solute and
solvent, respectively.
■. RESULTS AND DISCUSSION
⎛
⎞
⎟
ΔfusH Tm
1
x1γ
⎜
ln
=
− 1
Evaluation of Pure Component Properties. On the
basis of the results obtained by DSC and TGA analyses in
Figures 3 and 4, the melting point (Tm) is 412.36 K with the
⎝
⎠
RTm
T
(3)
1
where T and γ1 represent the equilibrium temperature and the
activity coefficients of the solute, respectively.
The plot of the mole-fraction solubility data of PAETE is
shown in Figure 5. It can be seen that the solubility of PAETE
in each of the given solvents is the function of temperature. It
increases with the increase of temperature. However, there are
Figure 3. Experimental heat Q flow from DSC measurement of
PAETE.
expanded uncertainty of 0.26 K; the enthalpy of fusion (ΔfusH)
for PAETE is 44.23 kJ·mol−1 with the expanded uncertainty of
0.35 kJ·mol−1. TGA curves in Figure 4 illustrate that the
decomposition of PAETE is one single step, and the char
residue is about 27%, showing that the PAETE can be applied
as intumescent flame retardant without the char-forming agent.
ΔfusS for PAETE calculated by eq 2 is 107.25 J/(mol·K).
Figure 5. Mole fraction solubility (x) data of PAETE in selected
ΔfusH
Tm
ΔfusS =
□
solvents and modeling with the modified Apelblat model:
chloroform; , acetone; , ethyl acetate; , ethanol; ☆, benzene;
,
(2)
○
△
▽
■
▼
▲
, tetrahydrofuran; , methanol; , acetonitrile; ★ methyl acetate;
Solubility Data and Correlation Models. The mole
fraction solubility of PAETE in chloroform, acetone, ethyl
◆
, toluene;.
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some differences in the increment of solubility with temper-
ature in different solvents. At a given high temperature (above
318.15 K), the order of solubility of PAETE is as follows:
chloroform > tetrahydrofuran > methanol > acetone > ethanol
> ethyl acetate > methyl acetate > acetonitrile > benzene >
toluene, but at low temperature (below 298.15 K), the order
changes to chloroform > tetrahydrofuran> acetonitrile > ethyl
acetate > acetone ≈ methyl acetate ≈ methanol ≈ ethanol >
benzene > toluene. The solubility of PAETE in toluene is the
lowest, whereas that in chloroform is the highest. The higher
solubility in chloroform than those in the other solvents might
be related to the strong electronegativity of the chlorine
element. PAETE can be used as the proton donor or acceptor
due to the existence of both NH and PO groups. That the
solubility in tetrahydrofuran is higher than that in alcohols
shows that the PAETE is the proton donor. Accordingly, it may
be that the hydrogen bonds between tetrahydrofuran and
PAETE molecules contribute to the higher solubility of PAETE
in tetrahydrofuran for ten solvents. It can be seen that
tetrahydrofuran and chloroform are more appropriate solvents
for the crystallization of PAETE from the solubility data. The
two solvents are also suggested as the appropriate reaction
solvents.
The solubility behaviors of the different solute in the same
solvent were affected not only by the intermolecular interaction
and the ability of the forming of a hydrogen bond between the
solvent and the solute, but also by the molecular structure of
the solute. PAETE has almost the similar molecular structure to
the PAPBE,20 but in the same selected solvents at the same
condition, the solubility of PAETE is greater than that of
PAPBE. For PAETE and PNBE,22 the solubility of PNBE is
greater than that of PAETE in the same selected solvents at the
same condition. These phenomenona may be due to the rigid
structure of the molecule of PAPBE and the molecular
asymmetry of PNBE.
The solute−solvent intermolecular interaction can be
estimated by the solute activity coefficients γi in a saturated
solution. γi < 1 means that the solutions positively deviate from
Raoult’s law and repulsive interactions exist between PAETE
and the solvent molecules. The systems of chloroform and
tetrahydrofuran exhibit positive deviations from ideality,
whereas the others exhibit negative deviations deviations from
ideality.
The relationship between temperature and mole fraction
solubility in the selected solvents can be calculated by the ideal
model, the modified Apelblat equation and the λ h equation.
The temperature dependence of the solubility for PAETE in
the selected solvents can be represented by the following ideal
model
The experimental data of solubility can be described by the λ
h equation as follows
⎡
⎤
⎛
⎞
λ(1 − x1)
1
T
1
Tm
ln 1 +
= λh
−
⎢
⎥
⎦
⎜
⎝
⎟
⎠
x1
⎣
(6)
Herein, λ and h denote two model parameters. λ discloses the
nonideality of the solution. h reflects the excess mixing enthalpy
of solution.
The ideal model, modified Apelblat equation, and λ h model
parameters could be obtained via fitting the experimental
solubility data and minimizing the following objective function:
Np
F
=
(x exp,i − x1cal,i 2
)
∑
obj
1
j=1
(7)
where x1exp,i, x1cal,i, Np refer to the experimental value, the
calculated value, and the number of data points, respectively.
The difference between the measured and calculated data was
identified by the relative standard deviations (RSDs), defined
by eq 9
1/2
2
⎡
⎢
⎤
⎥
N
calcd
⎛
⎝
⎞
⎠
xi − xi
1
⎜
⎜
⎟
⎟
RSD =
∑
⎢
⎣
⎥
⎦
N − 1
xi
i=1
(8)
where N denotes the total number of experimental points; xi
and xicalcd refer to the experimental solubility and the calculated
solubility, respectively.
The corresponding results of the parameters and rmsds of
the five models mentioned above are shown in Tables 2, 3, 4,
Table 2. Regressed Parameters and RSDs for the Ideal
Model
solvent
methanol
A
B
RSD%
16.877
16.419
7.1522
8.5029
9.9938
14.572
16.532
7.3119
11.346
3.9404
−6772.6
−6657.9
−3354.7
−4200.2
−4146.2
−6132.8
−7071.5
−4383.5
−5148.6
−2800.2
1.58
1.47
1.26
1.75
1.42
1.84
1.94
1.60
1.59
1.16
1.56
acetone
tetrahydrofuran
ethyl acetate
chloroform
ethanol
benzene
toluene
methyl acetate
acetonitrile
overall
Table 3. Regressed Parameters and RSDs for the Modified
Apelblat Equation
B
T
ln x1 = A +
(4)
solvent
methanol
A
B
C
RSD%
−101.26
−1302.3
−6092.0
−7935.4
−4367.9
−6959.9
−4273.0
−9336.2
−625.38
−878.90
−4146.3
17.515
1.8263
0.89
1.47
0.90
1.75
1.32
1.73
1.77
1.31
1.35
1.12
1.36
where T represents the equilibrium temperature in kelvin; A
and B refer to the parameters of the equation, respectively.
The correlation of the solubility and the temperature can be
expressed by the modified Apelblat equation as follows:
acetone
4.1156
tetrahydrofuran
ethyl acetate
chloroform
ethanol
106.72
12.080
−14.779
−0.52913
−9.0797
5.8707
71.163
B
T
−25.112
64.835
ln x1 = A +
+ Cln(T)
(5)
benzene
−7.1455
12.037
toluene
−73.874
−81.456
33.021
Herein, A, B, and C refer to empirical constants. The values of
A and B are the variation in the solution activity coefficient. The
C value discloses the effect of temperature on the fusion
enthalpy.
methyl acetate
acetonitrile
overall
13.775
−4.3117
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Table 4. Regressed Parameters and RSDs for the λh
Equation
solvent
methanol
λ
h
RSD%
0.61682
0.50725
0.15234
0.071191
0.40749
0.28911
0.20405
0.013401
0.12129
0.021744
11089
13223
22623
59571
10555
21435
34805
327516
42691
129660
1.86
1.52
1.14
1.75
1.35
2.05
1.85
1.61
1.63
1.16
1.59
acetone
tetrahydrofuran
ethyl acetate
chloroform
ethanol
benzene
toluene
methyl acetate
acetonitrile
overall
respectively. From Tables 2−4, the calculated data of PAETE in
the ten selected pure organic solvents agree well with the
experimental data. The order of the overall RSDs of the three
models mentioned above is as follows: the λ h eq (1.59%) > the
ideal model (1.56%) > the modified Apelblat eq (1.36%).
Compared with the ideal model and the λ h equation for these
systems, the modified Apelblat equation is more accurate
because the modified Apelblat equation was proposed by taking
the complex formed by the solute and solvent molecules into
account. The parameter λ is approximately considered as the
mean association number of solute molecules in solution for
the λ h equation. In Table 4, it can be seen that there is no
obvious association when the PAETE dissolves in these
solvents.
Figure 6. Residual function Y for PAETE versus solvent solubility
■
parameters δ2. , experiment data; , regression line to experimental
data, Y = −46.939δ2 + 531.9 (R2 = 0.9971).
Table 5. Solubility Parameter, δ, for Selected Solvents and
PAETE
solvent
δi
106Vi
1/2
(J·cm−3
)
m3·mol−1
methanol
29.52
26.42
19.44
24.09
18.35
19.13
19.03
18.71
18.35
19.77
23.27
40.70
58.52
81.50
52.68
98.59
81.94
80.66
89.48
106.60
73.93
401.00
ethanol
methyl acetate
acetonitrile
ethyl acetate
tetrahydrofuran
chloroform
benzene
Evaluation of the Solubility Parameter δ1 of PAETE.
The Scatchard−Hildebrand activity coefficient model, used to
describe the binary system, can be shown as follows:
2
RTln γ = Vφ (δ1 − δ2)2
(9)
1
1
2
toluene
acetone
x2V
2
φ2 =
PAETE
x2V + x1V1
(10)
2
⎡
⎤
∂ln x1
∂ln T
Here, δ1 (δ 2), ϕ2, and V1 (V2), denote the solubility parameters
of the solute (solvent), the volume fraction of solvent in the
binary mixture, the molar volume of the subcooled liquid of
pure solid solute (solvent), respectively.
The solubility parameter δ1 of PAETE was obtained from the
slope of the equation as follows and can be rearranged from
Scatchard−Hildebrand model
ΔH = RT
= R(−B + CT)
⎢
⎣
⎥
⎦
d
(12)
(13)
⎡
⎤
∂ln x1
∂ln T
ΔS = R
+ ln x = R[A + C(1 + ln T)]
⎢
⎣
⎥
d
1
⎦
The values of ΔHd and ΔSd of solutions at measured
solubility points were calculated and listed in Supporting
Informaiton Table S2. The calculated values ΔHd > 0 means
that the dissolving process of PAETE is endothermic.
Additionally, the entropy increases in the dissolving process
for the experimental temperature range. The endothermic
process of dissolution indicates that the interactions between
PAETE molecule and solvent molecules are stronger than those
between the solvent molecules. The positive ΔHd and ΔSd in
the systems show that the processes involved in dissolving
PAETE in the selected solvents are endothermic, entropy-
driven, and not spontaneous.23
RTln γ
1
2
2
Y =
− δ2 = −2δ1δ2 + δ1
2
Vφ
(11)
1
2
Based on the above equation, the linear dependence between
Y and δ at 298.15 K is presented in Figure 6. The molar
2
volume of PAETE is estimated to be 401.00 cm3·mol−1 by the
advanced chemistry development (ACD/Laboratories) Soft-
ware V11.02 at 293.15 K (press: 760 Torr) and is listed in
Table 5. The solubility parameters of the solvent can be gotten
from the literature22 and are also listed in Table 5. The
obtained parameter δ1 of PAPBE is 23.27(J·cm−3)1/2 and is also
showed in Table 5.
■. CONCLUSIONS
Thermodynamic Properties for the Solution. According
to the modified Apelblat equation, the dissolution enthalpy
ΔHd and the dissolution entropy ΔSd at saturation can be
calculated by the equations as follows:
The PAETE was synthesized in the work. The solubility data of
PAETE in chloroform, acetone, ethyl acetate, ethanol, benzene,
tetrahydrofuran, methanol, acetonitrile, methyl acetate, and
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Properties of Arylamine-Based Polybenzoxazines. J. Appl. Polym. Sci.
2013, 130, 1074−1083.
toluene were determined at different temperatures. The
chloroform, acetone, ethyl acetate, ethanol, benzene, tetrahy-
drofuran, methanol, acetonitrile, methyl acetate, and toluene
and the melting temperature were measured by DSC. At a
given high temperature (above 318.15 K), the order of
solubility for PAETE is as follows: chloroform > tetrahydrofur-
an > methanol > acetone > ethanol > ethyl acetate > methyl
acetate > acetonitrile > benzene > toluene, and at low
temperature (below 298.15 K) the order changes to chloroform
> tetrahydrofuran> acetonitrile > ethyl acetate > acetone ≈
methyl acetate ≈ methanol ≈ ethanol > benzene > toluene.
The experimental data were correlated with the modified
Apelblat equation, Ideal model, Scatchard−Hildebrand model,
and Buchowski−Ksiazczak model. The results show that,
compared with the other models, the modified Apelblat
equation is more suitable in determining the solubility of
PAETE. Based on the modified Apelblat model, the dissolution
enthalpy and entropy of PAETE are determined in different
solvents at saturation.
(8) Rakotomalala, M.; Wagner, S.; Doring, M. Recent Developments
in Halogen Free Flame Retardants for Epoxy Resins for Electrical and
Electronic Applications. Materials 2010, 3, 4300−4327.
(9) Xu, Y. Q.; Ding, T.; Fang, X. M. Preparation of Ethylenediamine
Bis(diphenyl phosphate) for Halogen-Free Flame-Retardant. Chinese
Patent CN 102532601 A 20120704, 2012.
(10) Arai, H.; Kondo, A. Halogen-Free Condensed Phosphate Ester
Amides or Their Salts, Their Aqueous Dispersion, and Fireproofing of
Fibers therewith. Japanese Patent JP 2010184887 A 20100826, 2010.
(11) Nguyen, C.; Kim, J. Thermal stabilities and Flame Retardancies
of Nitrogen-Phosphorus Flame Retardants based on Bisphosphor-
amidates. Polym. Degrad. Stab. 2008, 93, 1037−1043.
(12) Nazarova, Z. F.; Artemov, V. N.; Dyadchenko, A. I.; Baranova,
V. A.; Belyaeva, L. V. Fire- Resistant Polymer Composition. Soviet
Union Patent SU 990772 A1 19830123, 1983.
(13) Aoki, K.; Nakahama, T.; Mimura, K. Phosphoric Acid Amides.
Japanese Patent JP 54019919 A 19790215, 1979.
(14) Zhang, H.; Yin, Q. X.; Liu, Z. K.; Gong, J. B.; Bao, Y.; Zhang, M.
J.; Hao, H. X.; Hou, B. H.; Xie, C. Measurement and Correlation of
Solubility of Dodecanedioic Acid in Different Pure Solvents from T =
(288.15 to 323.15) K. J. Chem. Thermodyn. 2014, 68, 270−274.
(15) Apelblat, A.; Manzurola, E. Solubilities of O-acetylsalicylic, 4-
aminosalicylic, 3,5-initrosalicylic, and P-toluic Acid, and Magnesium-
DL-aspartate in Water from T (278 to 348) K. J. Chem. Thermodyn.
1999, 31, 85−91.
(16) Grand, D. J. W.; Mehdizadeh, M.; Chow, A. H. L.; Fairbrother,
J. E. Non-linear Van’t Hoff Solubility-temperature Plots and Their
Pharmaceutical Interpretation. Int. J. Pharm. 1984, 18, 25−38.
(17) Chol, P. B.; Mclaughlln, E. Solubility of Aromatic Hydrocarbon
Solids in Pyridine and Thiophene. Ind. Eng. Chem. Fundam. 1983, 22,
46−51.
(18) 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.
(19) Du, C. J.; Wang, L. S.; Yu, G. M.; Sun, G. Q. Solid−Liquid
Phase Equilibrium of N,N′- (Methylenedi-4,1-phenylene)bis-
(phosphoramidic acid) Tetraphenyl Ester in Selected Solvents. Ind.
Eng. Chem. Res. 2013, 52, 10916−10923.
(20) Du, C. J.; Wang, L. S.; Yu, G. M.; Qi, C. M. Solubilities of
Phosphonic Acid, P,P′-(1,4- Piperazinediyl)bis-P,P,P′,P′-tetraphenyl
Ester in Selected Solvents. J. Chem. Eng. Data 2013, 58, 2768−2774.
(21) Shao, X. Z.; Wang, L. S.; Li, M. Y. Measurement and Correlation
of the Solubilities of 2-[(6-oxido- 6H-dibenz[c,e][1,2]oxaphosphorin-
6-yl)methyl]butanedioic Acid in Selected Solvents. Ind. Eng. Chem. Res.
2012, 51, 5082−5089.
(22) Du, C. J.; Wang, L. S.; Yu, G. M.; Sun, G. Q. Solid-Liquid Phase
Equilibria of N,N ′-[l,3- Phenylenebis(methylene)]-bis-
(phosphoramidic acid) P,P,P ′,P ′-Tetraphenyl Ester in 10 Pure
Solvents. J. Chem. Eng. Data 2014, 59, 1533−1539.
(23) Prausnitz, J. M.; Lichtenthaler, R. N.; Azevedo, E. G. Molecular
Thermodynamics of Fluid-Phase Equilibria; Prentice Hall: New York,
1999.
ASSOCIATED CONTENT
* Supporting Information
■
S
MS spectra of PAETE, IR spectra of PAETE, 1H NMR spectra
of PAETE, 13C NMR spectra of PAETE, mole fraction
solubilities and activity coefficients of PAETE, and calculated
values for dissolution enthalpy and dissolution entropy of
PAETE in different pure solvents. The Supporting Information
is available free of charge on the ACS Publications website at
DOI: 10.1021/je5010565.
AUTHOR INFORMATION
Corresponding Author
*E-mail: lijuanw123@163.com. Tel.: +86-377-63513540. Fax:
+86-377-63168316.
■
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.
Notes
The authors declare no competing financial interest.
REFERENCES
■
(1) Howell, B. A.; Carter, K. E. Thermal Stability of Phosphinated
Siethyl Tartrate. J. Therm. Anal. Calorim. 2010, 102, 493−498.
(2) Horrocks, A. R.; Price, D. Fire Retardant Materials; CRC Press:
Boca Raton, FL, 2001.
(3) Tang, Y.; Zhao, Q. L.; Zeng, K.; Miao, P. K.; Zhou, K.; Tang, W.
R.; Zhou, H. F.; Liu, T.; Wang, Y. P.; Yang, G. C. Synthesis of a
Benzoxazine Monomer Containing Maleimide and Allyloxy Groups.
Chem. Lett. 2007, 18, 973−976.
(4) Tsutomu, T.; Takehiro, K.; Tarek, A. High Performance
Polybenzoxazines as a Novel Type of Phenolic Resin. Polym. J.
2008, 40, 1121−1131.
(5) Chen, L. J.; Song, L.; Lu, P.; Jie, G. X.; Tai, Q. L.; Xing, W. Y.;
Hua, Y. A New Intumescent Flame Retardant Containing Phosphorus
and Nitrogen: Preparation, Thermal Properties and Application to UV
Curable Coating. Prog. Org. Coat. 2011, 70, 59−66.
(6) Kandola, B. K.; Horrocks, A. R. Complex Char Formation in
Flame-Retarded Fibre-Intumescent Combinations-II. Thermal Ana-
lytical Studies. Polym. Degrad. Stab. 1996, 54, 289−303.
(7) Sarawut, R.; Nuttiwan, T.; Nitinat, S.; Chanchira, J.; Tsutomu, T.;
Sunan, T. Effect of Triphenyl Phosphate Flame Retardant on
1698
DOI: 10.1021/je5010565
J. Chem. Eng. Data 2015, 60, 1693−1698