Synthesis and Solubility of 5,5-Dimethyl-2-(phenyl(phenylamino)methyl)-1,3,2-dioxaphosphinane 2-oxide in Selected Solvents between 278.15 K and 347.15 K

Article abstract of DOI:10.1021/acs.jced.7b00585

A flame retardant with enhanced phosphorus-nitrogen content, 5,5-dimethyl-2-(phenyl(phenylamino)methyl)-1,3,2-dioxaphosphinane 2-oxide (DPPO), was synthesized by the reaction of 5,5-dimethyl-1,3,2-dioxaphosphinane 2-oxide (DDPO) with N-benzylideneaniline. The structure of DPPO was characterized by nuclear magnetic resonance (¹H NMR and ³¹P NMR) and Fourier transform infrared (FT-IR) spectroscopy. The thermal stability of DPPO was characterized by thermogravimetric analysis (TGA). The solubilities of DPPO were measured in different solvents including ethyl acetate, methanol, chloroform, acetonitrile, acetone, 1,2-dichloroethane, 1,4-dioxane, dichloromethane, tetrachloromethane, benzene, tetrahydrofuran, and isopropanol at temperature ranging from 278.15 to 347.15 K by the gravimetrical method. The mole fraction solubilities of DPPO in the above-mentioned organic solvents were correlated as the Apelblat equation, and the calculated values with equations shows good consistency with the experimental values. The root-mean-square deviation was less than 0.1%, and the average relative error was less than 0.04 in all of the experiments.

Full text of DOI:10.1021/acs.jced.7b00585

Article
pubs.acs.org/jced
Cite This: J. Chem. Eng. Data XXXX, XXX, XXX-XXX
Synthesis and Solubility of 5,5-Dimethyl-2-
(phenyl(phenylamino)methyl)-1,3,2-dioxaphosphinane 2‑oxide in
Selected Solvents between 278.15 K and 347.15 K
Xiao Ma,† Qianqiong Zhao,† Qianwen Liu,† Yalin Xing,† Ruilan Fan,*,† and Rongkai Tian‡
†Inner Mongolia Key Laboratory of Fine Organic Synthesis, College of Chemistry and Chemical Engineering, Inner Mongolia
University, Hohhot 010021, P. R. China
‡Department of Chemical and Biomolecular Engineering, The University of Melbourne, Melbourne 3053, Australia
ABSTRACT: A flame retardant with enhanced phosphorus−nitrogen
content, 5,5-dimethyl-2-(phenyl(phenylamino)methyl)-1,3,2-dioxaphosphi-
nane 2-oxide (DPPO), was synthesized by the reaction of 5,5-dimethyl-
1,3,2-dioxaphosphinane 2-oxide (DDPO) with N-benzylideneaniline. The
structure of DPPO was characterized by nuclear magnetic resonance (1H
NMR and 31P NMR) and Fourier transform infrared (FT-IR) spectroscopy.
The thermal stability of DPPO was characterized by thermogravimetric
analysis (TGA). The solubilities of DPPO were measured in different solvents
including ethyl acetate, methanol, chloroform, acetonitrile, acetone, 1,2-
dichloroethane, 1,4-dioxane, dichloromethane, tetrachloromethane, benzene,
tetrahydrofuran, and isopropanol at temperature ranging from 278.15 to
347.15 K by the gravimetrical method. The mole fraction solubilities of DPPO
in the above-mentioned organic solvents were correlated as the Apelblat
equation, and the calculated values with equations shows good consistency
with the experimental values. The root-mean-square deviation was less than 0.1%, and the average relative error was less than
0.04 in all of the experiments.
containing nitrogen and cyclic phosphorus are particularly
thermally stable and useful as flame retardants for polymeric
materials.2,3 Owing to the synergism between nitrogen and
cyclic phosphorus, it shows an excellent charring effect
associated with polymeric materials.
INTRODUCTION
■
For environment concerns, halogen-free flame retardation has
aroused great attention in recent years, because halogen-
The purpose of this study is to synthesize a nitrogen and
cyclic phosphorus-containing compound intumescent flame
retardant. The single additive leads to good miscibility with the
polymer matrix and good interface stability. An efficient
nitrogen and cyclic phosphorus containing compound, 5,5-
dimethyl-2-(phenyl(phenylamino)methyl)-1,3,2-dioxaphosphi-
nane 2-oxide (DPPO; chemical formula C18H22NO3P; CAS
Reg No. 77806-88-3; molecular weight 331.35; chemical
structure shown in Figure 1), has been synthesized. As we
know that solution crystallization is an important unit operation
in separation and purification for a compound in an industrial
process,3,4 the solubilities of organic compounds in different
solvents play a role in crystallization isolation procedures. To
identify the proper solvent and temperature range for the
crystallization process, many contributions of the solvent and
solute still need to be investigated experimentally. Among all of
the factors, both temperature and solvent are considered as the
most two important ones. Complete and accurate solubility
Figure 1. Structure of 5,5-dimethyl-2-(phenyl(phenylamino)methyl)-
1,3,2-dioxaphosphinane-2-oxide (DPPO).
containing flame retardant materials produce a lot of smoke and
toxic gases during burning.1 An organic phosphorus−nitrogen
flame retardant is considered as a promising halogen-free flame
retardant additive due to its advantages of low smoke, low
toxicity, low corrosion, and no molten dropping during a fire.
The efficiency of phosphorus-based flame retardant depends
upon not only the amount of the phosphorus element existing
in the compound but also the ability to form the charred
residues. More phosphorus volatiles playing the roles of active
species in the gas phase are generated during the decom-
position of combusting polymeric material.2 On the other hand,
the species enabling the formation of stable residual char is
more desirable for the polymer where the main mechanism is
based on the gas phase mode of action. The compounds
Received: June 26, 2017
Accepted: October 31, 2017
© XXXX American Chemical Society
A
DOI: 10.1021/acs.jced.7b00585
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Journal of Chemical & Engineering Data
Article
data can provide important foundation for solvent selection in
the synthesis and purification of compounds. Therefore,
inexpensive and effective solvents for the compound synthesis
and recrystallization have been found and then can be a guide
for the compound for industrial production. A higher purity of
DPPO is required in the application of the polyurethane flame
retardant. To further improve and optimize the process of
recrystallization and purification, it is imperative for us to know
the solubility of DPPO in a variety of organic solvents at
different temperatures. However, a systematic study of the
solubility of this nitrogen and cyclic phosphorus containing
flame retardant in different solvent systems has not been
reported.
In this work, the solubilities of DPPO in different organic
solvents, including ethyl acetate, methanol, chloroform,
acetonitrile, acetone, 1,2-dichloroethane, 1,4-dioxane, dichloro-
methane, tetrachloromethane, benzene, tetrahydrofuran, and
isopropanol, were measured at a designated temperature range
from 278.15 to 347.15 K at atmospheric pressure by the
gravimetrical method. The mole fraction solubilities (x) in the
mentioned solvents were correlated as the Apelblat equation,
and the calculated values with this equation showed good
consistency with experimental values. This aim of this study is
to provide basic information for the separation, purification,
and application of DPPO.
Figure 2. schematic diagram of solubility apparatus: 1, thermometer;
2, sample export; 3, rubber plug; 4, equilibrium cell; 5, magneton; 6,
magnetic stirrer apparatus; 7, water cycling bath; 8, rubber pipe.
Scheme 1. Synthesis Route of DDPO
EXPERIMENTAL SECTION
Chemicals Used. All of the solvents, ethyl acetate,
methanol, chloroform, acetonitrile, acetone, 1,2-dichloroethane,
■
Scheme 2. Synthesis Route of DPPO
Table 1. Chemical Compounds Used in the Study
purity (mass
fraction)
analysis
method
chemicals
acetone
source
b
d
Tianjinbeilian
Tianjinbeilian
Tianjinbeilian
Tianjinbeilian
Tianjinbeilian
Tianjinbeilian
Tianjinbeilian
Tianjinbeilian
≥0.995
≥0.998
≥0.997
≥0.990
≥0.995
≥0.995
≥0.995
≥0.995
≥0.995
≥0.995
≥0.997
≥0.995
≥0.995
GC
d
acetonitrile
GC
d
chloroform
GC
shows the schematic diagram of the experimental setup. A
jacketed equilibrium cell was used for the solubility measure-
ment with a working volume of 120 mL and a magnetic stirrer.
A circulating water bath was applied with a thermostat (type 50
L, made from Changzhouzhibirui Laboratory Instrument Work
Co., Ltd.), which is capable of maintaining the temperature
within 0.05 K. The melting point was determined by a X4
micro melting point apparatus (Beijing Fukai Instrument Co.,
Ltd.). An analytical balance (BAS124S) with an uncertainty of
0.1 mg was used during the mass measurements.
Thermogravimetric analysis (TGA) was carried with a Netzasch
STA 409 PC thermogravimetric analyzer at a heating rate of 10
K/min under nitrogen from 307.13 to 955.45 K. IR spectra
[Fourier transform infrared (FT-IR)] was recorded on a
thermo 6700 FT-IR using KBr pellets. 1H NMR and 31P NMR
spectra were obtained with a Bruker AVANCE III 500. All
samples were run in triplicate, and the average value with the
standard deviation is reported.
Synthesis of 5,5-Dimethyl-1,3,2-dioxaphosphinane 2-
oxide (DDPO). The DDPO was prepared by the reaction as
follows: In a 100 mL three-necked around-bottomed flask
equipped with a magnetic stirrer, reflux condenser, thermom-
eter, and oil bath. First, 3.12 g (0.03 mol) of neopentyl glycol
and 9 mL of 1,2-dichloroethane were added and stirred for 30
min at room temperature. Second, 4.13 g (0.03 mol) of
phosphoryltrichloride was dropwise added to the reaction
mixture at 278.15 K. The reaction mixture was reacted for 3 h
d
1,2-dichloroethane
ethyl acetate
methanol
GC
d
GC
d
GC
d
1,4-dioxane
GC
d
dichloromethane
GC
d
tetrachloromethane Tianjinbeilian
GC
d
benzene
Tianjinbeilian
Tianjinbeilian
Tianjinbeilian
Tianjinbeilian
GC
d
isopropanol
tetrahydrofuran
succinic acid
distilled water
GC
d
GC
d
GC
prepared in the lab
a
c
DPPO
synthesized in the
lab
≥0.998
HPLC
a
DPPO = 5,5-dimethyl-2-(phenyl(phenylamino)methyl)-1,3,2-dioxa-
phosphinane 2-oxide, CAS Reg No. 77806-88-3, light-yellow solid
b
c
state. Tianjinbeilian Chemical Reagent Co,. Ltd. High-performance
liquid chromatography. Gas chromatography.
d
1,4-dioxane, dichloromethane, tetrachloromethane, benzene,
tetrahydrofuran, and isopropanol, were obtained from
Tianjinbeilian Chemical Reagent Co., Ltd. All of the chemicals
were used without further purification. They were all analytical-
grade research reagents, and their purities were higher than
0.99. The mass fraction purities for the organic solvents used
are listed in Table 1.
Apparatus. The apparatus for the solubility measurement is
identical to that described in detailed in the literature. Figure 2
B
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Article
1
Figure 3. H NMR spectrum of DPPO.
Table 2. Experimental and Literature Mole Fraction
Solubility x of Succinic Acid in Water at Varied
a
Temperatures T and Pressure P = 0.1 MPa
T/K
1000x
T/K
1000x
experiment
283.65
289.00
293.75
298.25
303.15
308.06
312.85
317.77
322.55
327.45
333.15
337.50
342.25
6.63
8.37
literature
278.15
283.15
288.15
293.15
298.15
303.15
308.15
313.15
318.15
323.15
328.15
333.15
338.15
5.39
6.80
10.40
12.65
15.57
18.75
22.85
27.73
33.82
40.63
48.10
59.00
68.87
8.59
10.92
13.37
15.91
19.28
23.84
29.61
3.55
42.37
48.62
60.23
Figure 4. TGA/DGA curves of DPPO.
a
Standard uncertainties u are u(T) = 0.01 K, u(P) = 0.05 MPa, and
at 318.15 K until HCl evolution has subsided. At last, 1.38 g
(0.03 mol) of ethanol was dropwise added to three-necked
round-bottomed flask at 278.15 K. The reaction mixture was
reacted for 4 h at reflux temperature. Then, the reaction
mixture was cooled to room temperature. After that was
obtained by removing solvent under reduced pressure, then the
compound as white solid was extracted from the residue with
petroleum ether and diethyl ether (2:1), yield: 64%, mp
329.15−330.15 K. The detailed synthesis route of DDPO was
shown in Scheme 1.
Synthesis and Characterization of 5,5-Dimethyl-2-
(phenyl(phenylamino)methyl)-1,3,2-dioxaphosphinane
2-Oxide (DPPO). The DDOP was synthesized by the P−
(O)−H group reaction with the imidogen group of Schiff base
ur(x) = 0.02.
forming a P−C bond via nucleophilic addition. The yield was
80% with a melting point of 473.15−475.15 K. DPPO was
prepared by the reaction in a 100 mL three-necked round-
bottomed flask equipped with a magnetic stirrer, reflux
condenser, thermometer, and oil batch, and proceeded as
follows. First, 3.1 g (0.02 mol) of DDPO and 15 mL of 1,4-
dioxane were placed in the three-neck flask. Second, 3.62 g
(0.02 mol) of Schiff base (2-(N-phenyliminomethyl)phenol)
and 30 mL of 1,4-dioxane were dropwise added to the reaction
mixture and allowed to react at 70 °C for 2 h. Subsequently, the
mixture was cooled to room temperature. The crude product
C
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1
Figure 5. H NMR spectrum of pure compound and its residue after solvent evaporation in the various solvents.
was then filtrated from the mixture and washed with acetone.
The residue was recrystallized by ethanol, and finally the light
yellow powder was obtained. The melting point of DPPO is
447.15−449.15 K, yield: 71%. The detailed synthesis route of
DPPO was shown in Scheme 2. On the basis of the above
analysis, the purity of DPPO used in this work was higher than
0.99. IR (KBr), 3415 cm−1 (N−H), 3087, 3062 cm−1 (Ar−H),
2965−2878 cm−1 (C−H), 1509−1602 cm−1 (CC in ph),
1254 cm−1 (PO), 1183 cm−1 (C−N), 1056 cm−1 (P−O−C),
magnetic stirrer as described in the literature. To prevent the
evaporation of solvent, the equilibrium cell was sealed by a
rubber stopper. The equilibrium cell was keep at a constant
temperature by circulating water bath with a thermostat (type
DC0520, made from Changzhou Laboratory Instrument Works
Co., Ltd.) with the uncertainty of 0.05 K. For each
measurement, excessive DPPO and moderate solvent were
added to the equilibrium cell which was sealed by a rubber
stopper. The equilibrium cell was stirred for 2−3 h to ensure
equilibrium at the constant temperature. Then the stirring was
stopped to allow any solid to settle down from the solution, and
the solution was kept still for 4−5 h. A preheated injector
withdrew 2 mL of the clear upper portion of the solution which
was transferred quickly to a previously weighed measuring vial
(m0). The vial was tightly and promptly closed and weighed
(m1) to obtain to mass of the sample (m1 − m0). After that, the
solvent in the vial was sufficiently evaporated by a vacuum
drying oven at about 333 K. The mass of the vial (m2) was then
obtained again. From the thermogravimetric analysis, the
decomposition temperature of DPPO was found to be around
464.15 K. Consequently, we can make certain that the DPPO
solute cannot be volatilized at a temperature used in the
vacuum evaporation of the solvent. Different dissolution times
were tested to determine a suitable equilibrium time. Once the
solubility was determined at one temperature, the residue
including excess solid was heated to another temperature, and
the determination procedure was carried out repeatedly. It was
discovered that 2 h was enough for DPPO to reach equilibrium
time in all solvents. The experimental mole fraction solubility in
different organic pure solvents is calculated by eq 1:3
1
754, 735, 697 cm−1 (ph). The H NMR spectra of DPPO are
1
shown in Figure 3. H NMR (DMSO-d6) ppm: δ = 0.87, 1.13
ppm (6H, 2CH3), δ = 3.83−4.42 ppm (4H, 2CH2), δ = 5.38−
5.45 ppm (1H, CH), δ = 6.35−6.38 ppm (1H, NH), δ = 6.51−
7.58 ppm (10H, 2Ph) 31PNMR (DMSO-d6) ppm: δ = 15.45
ppm.
Thermogravimetric Analysis. To determine thermal
properties of DPPO, the thermogravimetric analysis (TGA)
and differential thermogravimetry (DTG) of DPPO have been
conducted under nitrogen from 298.15 to 853.15 K. The
thermogravimetric curve of DPPO is shown in Figure 4. The
initial thermal decomposition temperature of DPPO was
around 464.15 K. The maximum thermal degradation rate of
DPPO was 2.6%/min at 526.15 K. The weight loss was 90% at
the temperature ranging from 465.15 to 528.15 K, and the char
residue yield at 536.75 K was 3.60%.
Solubility Measurement. The static equilibrium method
was used to determine the solubility of DPPO in different
organic solvent in including ethyl acetate, methanol, chloro-
form, acetonitrile, acetone, 1,2-dichloroethane, 1,4-dioxane,
dichloromethane, tetrachloromethane, benzene, tetrahydrofur-
an, and isopropanol in the present work. The static equilibrium
method was validated by experimental solubilities of succinic
acid in water compared with the solubilities in the literature.5
The data of experiment and literature were presented in Table
2. It indicated that our experimental method is correct. The
apparatus included a 120 mL jacketed glass vessel with a
m2 − m0
M1
xexptl
=
m2 − m0
M1
m1 − m2
M2
+
(1)
where M1 is the molar mass of DPPO and M2 is the molar mass
of the solvent. During our experiments, three parallel
D
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measurements were carried out at the same composition of
solvent for each temperature, and an average value was
calculated. Nuclear magnetic resonance [1H NMR (DMSO-
d6)] was employed to analyze the solid samples before and after
experiment. As shown in the Figure 5, the resulting patterns
showed that there were no solvent peaks in the solid residues.
By comparison of these spectra, there was no difference
between pure compound and its residue after solvent
evaporation in the various solvents. It could be concluded
that solid solvates were not formed in the solvents tested.
RESULTS AND DISCUSSION
The mole fraction solubilities (x) of DPPO were measured in
ethyl acetate, methanol, chloroform, acetonitrile, acetone, 1,2-
■
Figure 8. Mole fraction solubility data for DPPO in organic solvents:
■
▲
▼
●
, tetrahydrofuran; , 1,4-dioxane; , ethyl acetate; , benzene.
Solid lines, values calculated from the modified Apelblat equation.
method which had been clarified in previous work.6,7 The mole
fraction solubility values of DPPO are presented graphically in
Figures 6 to 8. All of the data are presented in Table 3.
It can be seen from Figures 6, 7, and 8 that, within the
experimental temperature range, the solubility of DPPO in 12
organic solvents increased with rising temperature. At same
temperature, the solubilities of DPPO in chloroform, 1,2-
dichloroethane, and dichloromethane were higher than those in
the other selected organic solvents. The solubility of DPPO in
chloroform is the largest than that in the other solvents at the
same temperature. If the temperature decreases from 327.75 to
283.15 K, the maximum solubility of DPPO decreases from
6.461 × 10−3 to 3.817 × 10−3. Among the 12 solvents, the
solubility of DPPO in chloroform is the most suitable solvent to
improve the purification process of DPPO. But the solubility of
DPPO in tetrachloromethane was lower than those in the other
selected organic solvents. It was deduced that the polarity in
solution might play a dominant role. As shown in Figure 7, the
solubilies of DPPO in isopropanol and methanol were lower
than those in the acetone, 1,4-dioxane, tetrahydrofuran,
acetonitrile, dichloromethane, 1,2-dichloroethane, and chloro-
form. Figure 8 shows the solubilities of DPPO in tetrahy-
drofuran, 1,4-dioxane, ethyl acetate, and benzene. The solubility
of DPPO in tetrahydrofuran is similar to its in 1,4-dioxane. The
solubility of DPPO in ethyl acetate is similar to its in benzene.
It further can be seen that solubilities of DPPO in
tetrahydrofuran and 1,4-dioxane were higher than those in
ethyl acetate and benzene. The order of solubility of DPPO is
as follows: chloroform > 1,2-dichloroethane > dichloromethane
> acetonitrile > (1,4-dioxane, tetrahydrofuran) > acetone >
methanol > (ethyl acetate, benzene) > isopropanol >
tetrachloromethane.
Figure 6. Mole fraction solubility data for DPPO in organic solvents:
■
●
▼
▲
, chloroform; , 1,2-dichloroethane; , tetrachloromethane; ,
dichloromethane. Solid lines, values calculated from the modified
Apelblat equation.
Figure 7. Mole fraction solubility data for DPPO in organic solvents:
The temperature dependence of the solubility of DPPO in
selected solvents is represented by the modified Apelblat
equation5,8−12 according to eq 2:
■
▲
▼
●
, acetonitrile; , acetone; , methanol; , isopropanol. Solid lines,
values calculated from the modified Apelblat equation.
B
T/K
ln x = A +
+ C ln(T/K)
dichloroethane, 1,4-dioxane, dichloromethane, tetrachlorome-
thane, benzene, tetrahydrofuran, and isopropanol at temper-
atures ranging from 278.15 to 347.15 K by the gravimetrical
(2)
with
E
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Table 3. Expermental Mole Fraction Solubility (xexp) of DPPO in Different Solvents at Varied Temperatures T and Pressure P =
a
0.1 MPa
a
b
c
b
c
solvent
T /K
x·1000
ε/%
solvent
acetonitrile
T/K
x·1000
ε/%
ethyl acetate
293.65
298.25
303.15
308.05
312.95
317.95
322.95
327.95
332.75
337.65
278.75
283.65
288.85
293.95
298.35
303.25
307.75
313.15
317.95
322.75
327.95
285.65
288.65
293.65
298.15
303.15
308.15
313.15
318.15
323.15
328.15
278.15
283.75
288.15
293.75
298.65
302.75
307.85
311.75
317.15
321.25
278.15
283.15
288.35
293.65
298.15
302.17
307.95
312.55
317.55
321.55
326.65
332.15
337.15
278.15
283.15
288.35
293.65
298.15
302.17
2.32
2.78
2.12
−5.08
3.24
278.00
285.65
288.75
293.75
298.25
303.25
308.15
312.75
317.65
322.45
327.75
335.35
278.65
283.65
288.65
293.25
298.15
303.15
308.25
313.15
318.15
323.15
328.15
333.15
278.15
283.65
289.15
293.65
298.15
303.15
307.95
313.15
318.15
323.15
278.65
283.25
288.65
293.25
298.85
302.95
308.35
310.95
278.65
283.65
288.15
293.25
298.25
303.15
307.95
313.15
318.05
322.65
327.15
332.65
337.55
343.15
347.5
5.57
6.80
2.01
−1.37
−1.74
0.12
3.85
7.46
4.60
−0.58
−0.23
0. 10
−0. 16
2.04
8.87
5.61
10.07
11.87
14.23
16.13
19.15
21.82
25.76
32.83
10.21
11.88
14.26
16.94
19.11
22.92
26.50
31.01
34.98
39.47
43.69
52.60
1.51
−1.26
−0.49
2.21
6.71
7.81
9.13
0.22
9.70
−2.99
1.09
1.81
11.12
35.22
38.17
40.34
41.96
44.42
47.15
49.16
52.67
54.84
59.10
64.61
6.09
−0.38
−0.63
−0.61
1.08
chloroform
2.12
−5.08
3.24
1,2-dichloroethane
−0.39
0.34
−1.59
−0.48
1.55
0.63
−0.52
−0.15
−2.04
−0.54
1.76
−2.02
0.82
0.28
2.00
0.28
1,4-dioxane
0.52
−0.92
−3.67
2.54
6.61
0.19
7.39
−3.18
1.67
8.87
methanol
−1.06
1.58
10.26
12.06
13.86
16.15
18.98
22.95
2.44
0.98
2.00
1.51
2.46
−2.00
2.66
−0.41
−1.27
−1.46
0.94
3.12
3.67
0.04
4.50
−0.17
−0.71
−0.81
−1.18
1.58
5.41
acetone
3.30
6.62
3.14
−5.61
1.30
7.96
4.32
9.84
5.78
0.37
dichloromethane
7.71
−1.21
2.82
7.28
−1.26
0.14
9.94
8.98
12.05
15.19
18.90
23.15
27.37
31.66
1.10
−2.29
0.77
11.20
13.75
17.13
18.59
0.15
−0.76
3.05
−1.16
2.16
3.27
−4.18
1.41
−2.81
1.55
tetrachloromethane
0.19
−5.00
−0.38
1.97
benzene
2.75
0.26
1.31
−2.41
−0.82
−1.03
−1.72
−0.58
3.86
0.34
1.62
0.44
5.29
2.01
0.51
−0.12
−1.16
2.03
2.45
0.66
3.01
0.85
3.81
1.03
−0.91
−2.28
−7.98
3.77
4.64
3.90
1.21
5.19
−3.08
0.30
1.43
6.34
2.03
7.11
−4.35
3.46
2.46
2.56
9.30
isopropanol
0.40
1.28
10.73
12.29
14.91
5.83
1.30
0.50
−0.58
0.69
−3.74
1.61
0.66
0.80
−5.53
0.86
tetrahydrofuran
278.65
283.65
288.15
2.39
1.06
6.48
−2.57
0.42
1.28
0.85
7.64
F
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Article
Table 3. continued
a
b
c
b
c
solvent
T /K
x·1000
ε/%
solvent
T/K
x·1000
ε/%
307.95
312.55
317.55
321.55
326.65
332.15
337.55
343.15
347.5
1.77
2.03
2.54
3.18
3.89
4.85
6.26
7.91
9.58
5.41
−2.04
−2.07
2.39
293.25
298.25
303.15
307.95
313.15
318.05
322.65
327.15
8.58
10.22
11.73
13.28
15.25
16.92
18.72
21.49
23.66
−2.80
0.59
1.03
0.77
−0.09
−2.25
0.18
1.31
−0.46
−1.46
1.78
−0.26
0.75
332.65
c
−1.14
a
b
Standard uncertainties u are u(T) = 0.01 K, u(P) = 0.05 MPa. Standard uncertainties u is ur(x) = 0.02. Relative deviations; εi = (xical − xiexpl)/
xiexpl*100%.
Table 4. Parameters of the Modified Apelblat Equation and Deviations for DPPO in Different Solvents
solvent
A
B
C
σ/%
RSD/%
R2
ethyl acetate
chloroform
450.4182
−80.4968
−198.7460
171.8738
−139.9639
20.0643
−24256.7641
2580.4258
−65.8000
12.0616
30.3096
−24.2066
21.6056
−2.1911
4.9040
1.7637
0.9690
1.1363
2.3233
1.0715
1.4355
1.1793
1.8469
2.6806
2.3264
1.6826
1.3939
0.1120
0.0116
0.0139
0.0289
0.0129
0.0173
0.0141
0.0199
0.0345
0.0267
0.0236
0.0160
0.9973
0.9949
0.9990
0.9976
0.9992
0.9963
0.9986
0.9975
0.9981
0.9987
0.9993
0.9985
1,4-dioxane
6354.2575
acetone
−11594.7676
3659.8377
acetonitrile
1,2-dichloroethane
methanol
−3434.1305
−2216.9068
−2741.0458
−2140.7668
−2138.3525
330.3769
−26.1125
−13.6825
−42.7908
−27.0389
−95.7275
0.0767
dichloromethane
tetrachloromethane
benzene
3.3154
7.4061
4.9515
isopropanol
tetrahydrofuran
15.4034
0.5362
−2302.8961
Table 5. Values of the Literature Parameters for Different
Solvents
Hilderbrand
dipole
dielectric
solubility
parameter (δH)
(293.15 K)
moments constant
solvent
ethanol
polarity
(μ)
(ε)
6.6
6.2
5.4
3.3
4.4
4.3
4.8
3.4
1.6
3.0
4.3
4.2
1.7
3.2
2.9
1.8
1.1
1.7
1.5
3.8
0
32.60
37.50
20.70
10.45
4.80
14.5
11.9
10.0
9.8
acetonitrile
acetone
1,2-dichloroethane
chloroform
9.3
ethyl acetate
1,4-dioxane
6.02
9.1
2.21
9.9
dichloromethane
tetrachloromethane
benzene
9.10
9.7
2.24
8.6
0
2.28
9.2
isopropanol
5.6
5.67
18.30
7.58
11.5
9.2
tetrahydrofuran
Figure 9. Temperature dependence of the solubility of DPPO in 12
■
▼
solvents: ◀, tetrachloromethane; , isopropanol; , ethyl acetate; ☆,
◆
●
△
benzene; , methanol; , acetone; , 1,4-dioxane; ★, tetrahydrofur-
an; , acetonitrile; , dichloromethane; ▶, 1,2-dichloroethane;
where x is the mole fraction solubility of DPPO and T (K) is
the absolute temperature. ΔfusH1 (J·mol−1) denotes the
enthalpy change upon the melting of the solute at the its
triple point temperature Tt1 (K), and ΔfusCp1 (J·K−1·mol−1) is
the difference between the heat capacities of the solute in the
liquid and solid phases. Both a and b are constants. R (J·mol−1·
K−1) is the molar gas constant.
By means of the nonlinear fitting of the experimental
solubility data, we can obtain the parameters A, B, and C, which
are shown in Table 4. The root mean-square deviations (RSD)
and the average relative deviations (σ) were used to distinguish
the discrepancy between the measured value and the calculated
data, respectively. The relative standard deviations (RSD),
defined by eq 6, are also present in Table 4.
□
◇
,
○
chloroform.
ΔfusCp1
ΔfusH
1
A =
−
(ln T + 1) − a
t1
RT
R
(3)
(4)
(5)
t1
ΔfusC
ΔfusH
R
p1 T − b
1
B = −
+
t1
R
ΔfusCp1
C =
R
G
DOI: 10.1021/acs.jced.7b00585
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1/2
2
order of solubility of DPPO is as follows: chloroform > 1,2-
dichloroethane > dichloromethane > acetonitrile > (1,4-
dioxane, tetrahydrofuran) > acetone > methanol > (ethyl
acetate, benzene) > isopropanol > tetrachloromethane. The
better solvents for DPPO are chloroform, dichloromethane,
1,2-dichloroethane, tetrahydrofuran, and acetonitrile, but for
the recrystallization, acetonitrile, 1,2-dichloroethane, tetrahy-
drofuran, and acetone are suitable solvents. The calculated
values of DPPO by the Apelblat model were in good agreement
with the experimental data. The root-mean-square deviation
(RSD) was less than 0.1%, and the average relative error was
less than 0.04 in all of the experiments.
⎡
⎢
⎤
⎥
N
xiexp − xical
⎛
⎝
⎞
⎠
1
N
⎜
⎜
⎟
⎟
RSD =
∑
xiexp
⎢
⎣
⎥
⎦
i=1
(6)
where xiexp and xical stand for the experimental solubility and the
solubility calculated from Apelblat equation, respectively; N
represents the number of experimental data points.The relative
deviation εi is defined as
xiexp − xical
εi =
× 100%
xiexp
(7)
The average relative error σ is defined as#tab;
AUTHOR INFORMATION
n
xiexp − xical
■
1
n
σ =
× 100%
∑
Corresponding Author
*E-mail: ruilanfan@imu.edu.cn. Tel.: +86-0471-4992982. Fax:
+86-0471-4992982.
xiexp
(8)
i=1
The results demonstrate that eq 2 can be applied to correlate
the solubility data with high accuracy from Figure 9, with the
temperature range of the measurement. It can be seen that the
solubilities of DPPO in a certain solvent increase with
increasing in temperature. The values of A, B, and C used in
the modified Apelblat equation, as well as the RSD and R2
value, were provided in Table 4. These data indicated that the
results of Apelblat equation match the experimental data for
DPPO in the 12 solvents over the temperature range from
278.15 to 347.15 K. The R2 values were from 0.9949 to 0.9993.
The RSD were all less than 0.1%, and the average relative error
was less than 0.04 in all of the experiments.
In general, it is too complicated to elucidate the solubility
behavior of DPPO in these solvents to assign to a single reason.
The solubility behavior of DPPO may result from many factors,
the properties of the solvents including the solubility
parameters (δ), the rule of “like dissolves like”, molecule
structure, dielectric constant (ε), the hydrogen bond, and van
der Waals forces and so on.13 For all of the selected solvents,
the properties including polarity, dipole moments (μ),
dielectric constant (ε), and Hilderbrand solubility parameter
(δH)14−16 are presented in Table 5. For the specific case of
chloroform, it was deduced that hydrogen bonds and polarity in
solution might play a dominant role.17,18 Because of the
electronic-withdrawing ability of chlorine atoms, the chloro-
form contains an active hydrogen. There are two oxygen atoms
in DPPO which can form different hydrogen bonds in the
chloroform, making DPPO very soluble in the chloroform in
agreement with the similar miscibility theory. All of the DPPO
molecules, 1,4-dioxane molecules, and tetrahydrofuran have a
hexatomic ring containing two oxygen atoms. Based on the
principle of “like dissolves like”, the solubility of DPPO in 1,4-
dioxane and tetrahydrofuran are relatively high. The polarities
of methanol and acetone are relative strong, so the DPPO
solubility in the three solvent is low. Therefore, the solubility of
DPPO do not display regularly variation in terms of the polarity
and molecule structure of solvents. Further research and
experiments need to be done to explore this phenomenon.
ORCID
Ruilan Fan: 0000-0002-1610-1653
Notes
The authors declare no competing financial interest.
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CONCLUSIONS
■
DPPO was prepared and characterized by IR and NMR. The
thermal stability of DPPO was characterized by thermogravi-
metric analysis (TGA). The solubilities of DPPO in 12 solvents
were measured by a gravimetrical method. For all of the
selected solvents studied, the solubility of DPPO was increased
with an increasing temperature. At ambient temperature, the
H
DOI: 10.1021/acs.jced.7b00585
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I
DOI: 10.1021/acs.jced.7b00585
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