Article pubs.acs.org/jced
Thermodynamic Difference between Protocatechualdehyde and p‑Hydroxybenzaldehyde in Aqueous Sodium Chloride Solutions Jimin Xie,† Min Liu,*,†,‡ Guiqin Liu,‡ Lixia Yuan,† Dacheng Li,‡ Zhiping Fan,‡ Zhengping Wang,‡ Bingquan Wang,‡ and Jun Han‡ †
School of Chemistry and Chemical Engineering, Liaocheng University, Liaocheng 252059, China Institute of BioPharmceutical Research, Liaocheng University, Liaocheng 252059, China
‡
S Supporting Information *
ABSTRACT: The enthalpies of dilution of protocatechualdehyde and p-hydroxybenzaldehyde in the aqueous sodium chloride solutions were measured by using a mixing-flow microcalorimeter at 298.15 K. Densities of the ternary homogeneous systems at different temperatures (293.15, 298.15, 303.15, 308.15, and 313.15 K) were also measured with a quartz vibratingtube densimeter. The homogeneous enthalpic interaction coefficients (h2, h3, and h4) were calculated according to the excess enthalpy concept based on the calorimetric data. The apparent molar volumes (Vϕ) and standard partial molar volumes (V0ϕ) of the investigated system were computed from their density data. The variation trends in h2 and V0ϕ with increasing salt molality were obtained and discussed in terms of the (solute + solute) and (solute + solvent) interactions. The experimental results showed that the molecular structures of protocatechualdehyde and p-hydroxybenzaldehyde, especially the number of hydroxyl groups, have evident influence on their thermodynamic properties. The thermodynamic data obtained in this work may be helpful for exploring the structure−function relationship of protocatechualdehyde and p-hydroxybenzaldehyde. verified to have anticancer effects.7,11,12 For example, it was suggested that PAL is likely to inhibit oncogenic disease through the inhibition of protein kinase CKII activity.7 p-Hydroxybenzaldehyde (4-hydroxybenzaldehyde, PHBA; Scheme 1b), a major active constituent of Gastrodiae rhizoma13 and vanilla bean,14 is an important intermediate for the production of fine chemicals and is extensively applied in medicine, perfume, cosmetic, and agrochemical industries.15,16 The molecular structures of PHBA and PAL are similar to the characteristics of a hydroxyl group and an aldehyde group attached to the C4 and C1 positions of a benzene ring, respectively. The difference is that PAL has an additional hydroxyl group at the C3 position. In comparison with PAL, PHBA is known mainly for its use as an intermediate. It is less known for its antioxidant activity.17,18 This difference of activity may be caused by their different structures, such as the number and position of the functional groups. The investigation of the physicochemical properties of phenolic compounds is helpful to understand both their efficacies and the role of each functional group. In recent years, several studies have been performed to determine the solubility, density, refractive index, and standard molar enthalpy of formation of PAL and PHBA.16,19−23 The equilibrium solubility of PHBA at different temperature, pressure, and solvent conditions were measured by Wu et al.16,19,20 The solubility of PAL in
1. INTRODUCTION Phenolic compounds have drawn increasing attention due to their great abundance in our diet, their antioxidant properties, and their effective prevention of oxidative stress associated diseases such as cancer and cardiovascular diseases.1,2 Phenolic compounds possess one or more aromatic rings with one or more hydroxyl groups. It has been reported that their antioxidant activity seems to be related to their molecular structure. More precisely, it is related to the presence and number of hydroxyl groups.3,4 Protocatechualdehyde (3,4-dihydroxybenzaldehyde, PAL; Scheme 1a) is a phenolic compound present in Salvia miltiorrhiza,5 barley tea6 and Xanthium strumarium and so on.7 A great deal of research has proven that PAL has antioxidant, anti-inflammatory, antihepatitis B virus, and antiatherosclerosis effects.5,8−10 More importantly, PAL has also been Scheme 1. Molecular Structures of PAL (a) and PHBA (b)
Received: June 5, 2016 Accepted: February 8, 2017 Published: February 21, 2017 © 2017 American Chemical Society
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DOI: 10.1021/acs.jced.6b00458 J. Chem. Eng. Data 2017, 62, 902−912
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Table 1. Specification of the Chemical Samples chem name a
PHBA PALb sodium chloride a
CAS no.
source
mass fraction purity (%)c
123-08-0 139-85-5 7647-14-5
J&K Chemical Ltd. (Beijing) J&K Chemical Ltd. (Beijing) Aladdin Bio-Chem Technology Co., Ltd. (Shanghai)
≥99.0 ≥99.0 99.8
p-Hydroxybenzaldehyde. bProtocatechualdehyde (3,4-dihydroxybenzaldehyde). cStated by the supplier.
supercritical carbon dioxide was measured by Beltrán et al.21 In our previous work, the influence of temperature and pH on the densities and refractive indices of PAL in aqueous phosphate buffer solutions was discussed in detail.24 The enthalpy of dilution, which can embody important information about (solute + solute) and (solute + solvent) interactions, is one of the basic thermodynamic properties.25−27 Volumetric property, especially standard partial molar volume, is very useful to explain the intermolecular interaction occurring in the investigated system.28−30 It is well-known that biological fluids of living organisms contain a specified quantity of ions, especially sodium, potassium, and chloride ions, which are indispensable for the metabolic processes of a living organism to proceed. Among various inorganic salts, sodium chloride is especially essential to our life. It is required for blood, sweat, digestive juices, and efficient nerve transmission. For example, sodium coupled neurotransmitter transporters cooperate with postsynaptic receptors to detect signaling by the presynaptic nerve cell in the form of exocytotically released transmitters.31 Therefore, the research of thermodynamic properties of PHBA and PAL in aqueous sodium chloride solutions is very important and necessary. Until now, however, there has been a paucity of information on the dilution enthalpy and volumetric property of PAL and PHBA in the aqueous salt solutions. In this work, and continuing our previous study, the enthalpies of dilution PHBA and PAL in the aqueous sodium chloride solutions were measured at 298.15 K. In addition, the densities of PHBA (PAL) + NaCl + H2O at different temperatures (293.15, 298.15, 303.15, 308.15, and 313.15 K) were also measured. The enthalpic interaction coefficients and standard partial molar volumes were obtained based on the values of the enthalpies of dilution and densities, respectively. The results were discussed in light of (solute + solute) and (solute + solvent) interactions. The resulting parameters may provide fundamental information for exploring the structure−function relationship of PHBA and PAL.
Thermometric 2277 thermal activity monitor (Thermometric, Jarfalla, Sweden) at 298.15 K. The molality ranges of the aqueous PAL and PHBA solutions were 0.0250−0.0900 and 0.0250−0.0800 mol·kg−1, respectively. Both PAL and PHBA solutions were prepared with water or aqueous sodium chloride solution of a certain molality as solvent. With the aid of a VS2-10R MIDI dual-channel pump, the PAL and PHBA solutions and the corresponding solvent were simultaneously pumped through the mixing-flow vessel and the reference vessel connected in sequence. The masses of the samples delivered in 6 min were collected and weighed to determine their flow rates. The uncertainties in the thermal power, the molality of solute, and the flow rate were ±0.2 μW, ±0.0001 mol·kg−1, and ±0.002 mg·s−1, respectively. The detailed description of the instrument and the measurement procedure for dilution enthalpy determination were set forth elsewhere.32 2.3. Density Measurement. Densities of the investigated binary and ternary solution systems were measured with an Anton Paar DMA-5000 vibrating-tube densimeter (Graz, Austria) in the temperature range from 293.15 to 313.15 K with an interval of 5 K. The density measurements were performed at atmospheric pressure. The precision of this densimeter was ±2 × 10−6 g·cm−3, and its temperature accuracy was ±0.01 K. Calibration was performed periodically under atmospheric pressure using deionized water and dry air according to the specifications provided by the manufacturer. The molality ranges of the aqueous PAL and PHBA solutions for the density measurement were 0.0100−0.0900 and 0.0100− 0.0500 mol·kg−1, respectively, owning to their solubility. During the measurements, the sample (ca. 5 cm3) was transferred to a syringe and some of the contents of the syringe were injected into the densimeter. Precautions were taken to avoid evaporation losses and air dissolved during the experiment. Triplicate measurements of each sample were conducted to obtain the average value of density. After each measurement, distilled water and anhydrous ethanol were used to clean the vibrating tube.
2. EXPERIMENTAL SECTION 2.1. Materials. Protocatechualdehyde (PAL), p-hydroxybenzaldehyde (PHBA), and sodium chloride used in this work were of the highest purity that were commercially available and used as supplied without further purification. The list of chemicals used along with their suppliers and mass fraction purities were given in Table 1. Deionized, doubly distilled, and degassed water prepared with a quartz sub-boiling purifier was used for preparation of all of the solutions. The solutions were prepared on a mass basis by using a Mettler Toledo AG 135 analytical balance with a precision of ±0.00001g. Aqueous sodium chloride solutions with the molality of 0.00−0.60 mol·kg−1 were prepared and then were used as solvent to prepare the ternary mixtures. All of the reagents were stored over P2O5 in a vacuum drier before use. 2.2. Calorimetric Measurements. The enthalpies of dilution for PAL and PHBA in sodium chloride solutions were performed with a 2277-204 measuring cylinder supported by a
3. RESULTS AND DISCUSSION 3.1. Enthalpy of Dilution. The enthalpic interaction coefficients, derived from McMillan−Mayer’s theory,33 and modified by Franks et al.,34 characterize the total energetic effects of interactions between the investigated solute molecules with the competitive participation of solvent molecules.35 Therefore, these coefficients can contribute to a better understanding of the effects of the molecular structures of solute molecules on their hydrophobic/hydrophilic properties. The enthalpic interaction coefficients (hn) can be obtained from multiple linear regression analyses by fitting the data of dilution enthalpy ΔdilHm to eq 1:36 Δdil Hm = HmE(mf ) − HmE(m i ) = h2(mf − m i) + h3(mf2 − m i2) + h4(mf3 − m i3) + ... (1) 903
DOI: 10.1021/acs.jced.6b00458 J. Chem. Eng. Data 2017, 62, 902−912
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Table 2. Enthalpies of Dilution of PHBA and PAL in Aqueous Sodium Chloride Solutions at 298.15 K and Atmospheric Pressure of 0.1 MPaa mi/(mol·kg−1)
mf/(mol·kg−1)
ΔdilHm/(J·mol−1)
0.0250 0.0300 0.0400 0.0450 0.0500
0.0110 0.0132 0.0177 0.0199 0.0221
150.99 176.66 226.19 250.46 274.61
0.0250 0.0300 0.0400 0.0450 0.0500
0.0112 0.0136 0.0181 0.0203 0.0227
164.02 190.49 243.81 271.18 294.68
0.0250 0.0300 0.0400 0.0450 0.0500
0.0109 0.0131 0.0175 0.0195 0.0219
140.46 164.92 209.49 232.56 252.03
0.0250 0.0300 0.0400 0.0450 0.0500
0.0105 0.0123 0.0167 0.0188 0.0209
163.14 197.04 248.61 274.79 298.96
0.0250 0.0300 0.0400 0.0450 0.0500
0.0114 0.0136 0.0182 0.0205 0.0227
162.93 193.03 249.08 275.74 303.53
0.0250 0.0300 0.0400 0.0450 0.0500
0.0107 0.0131 0.0176 0.0199 0.0219
178.55 206.27 259.10 283.70 309.73
0.0250 0.0300 0.0400 0.0450 0.0500
0.0106 0.0127 0.0168 0.0189 0.0212
166.57 197.73 257.49 283.98 307.28
0.0250 0.0300 0.0400 0.0450 0.0500 0.0550
0.0120 0.0141 0.0185 0.0206 0.0237 0.0254
337.59 389.92 492.11 547.77 577.60 633.28
0.0250 0.0300 0.0400 0.0450 0.0500 0.0550
0.0119 0.0143 0.0193 0.0217 0.0239 0.0263
354.44 405.21 499.24 546.81 596.59 640.46
δ/(J·mol−1) mNaCl = 0.01 −0.02 0.02 0.01 0.01 mNaCl = 0.03 −0.02 0.01 0.02 −0.03 mNaCl = 0.04 −0.04 −0.01 0.03 0.02 mNaCl = 0.02 −0.03 0.01 0.01 0.02 mNaCl = 0.01 −0.02 0.01 0.03 0.01 mNaCl = 0.03 −0.04 −0.01 0.02 0.02 mNaCl = 0.02 −0.05 −0.03 0.03 0.04 mNaCl = −0.02 −0.03 0.04 −0.01 0.01 −0.02 mNaCl = −0.01 −0.02 0.03 −0.03 0.04 −0.01
mi/(mol·kg−1)
PHBA 0.0000 mol·kg−1 0.0550 0.0600 0.0650 0.0700 0.0800 0.1000 mol·kg−1 0.0550 0.0600 0.0650 0.0700 0.0800 0.2000 mol·kg−1 0.0550 0.0600 0.0650 0.0700 0.0800 0.3000 mol·kg−1 0.0550 0.0600 0.0650 0.0700 0.0800 0.4000 mol·kg−1 0.0550 0.0600 0.0650 0.0700 0.0800 0.5000 mol·kg−1 0.0550 0.0600 0.0650 0.0700 0.0800 0.6000 mol·kg−1 0.0550 0.0600 0.0650 0.0700 0.0800 PAL 0.0000 mol·kg−1 0.0600 0.0650 0.0700 0.0750 0.0800 0.0900 0.1000 mol·kg−1 0.0600 0.0650 0.0700 0.0750 0.0800 0.0900
904
mf/(mol·kg−1)
ΔdilHm/(J·mol−1)
δ/(J·mol−1)
0.0243 0.0264 0.0288 0.0310 0.0351
297.49 321.93 342.19 364.53 411.69
−0.01 0.01 −0.02 −0.03 −0.02
0.0247 0.0272 0.0293 0.0316 0.0362
322.51 343.81 368.52 391.39 435.42
−0.01 0.03 −0.04 −0.02 0.01
0.0240 0.0261 0.0282 0.0305 0.0349
272.38 293.32 314.80 334.20 376.03
−0.01 −0.02 −0.02 −0.01 −0.01
0.0230 0.0250 0.0272 0.0291 0.0335
323.28 347.87 369.96 394.97 437.30
0.03 −0.02 −0.02 −0.03 0.01
0.0249 0.0273 0.0296 0.0318 0.0360
330.31 353.83 377.84 404.60 458.45
−0.02 −0.01 0.03 −0.01 −0.01
0.0241 0.0262 0.0284 0.0306 0.0354
333.95 358.50 381.82 404.95 449.15
0.03 −0.02 −0.01 −0.02 −0.02
0.0229 0.0252 0.0274 0.0293 0.0337
336.96 358.49 381.47 408.73 459.85
0.02 0.04 0.03 −0.05 0.02
0.0274 0.0300 0.0322 0.0348 0.0377 0.0410
669.19 723.20 759.00 797.80 815.77 893.43
−0.02 −0.02 0.01 −0.01 0.03 −0.03
0.0282 0.0309 0.0336 0.0357 0.0374 0.0425
692.32 727.10 759.13 800.46 848.43 899.82
−0.04 −0.01 0.04 0.02 −0.05 0.02
DOI: 10.1021/acs.jced.6b00458 J. Chem. Eng. Data 2017, 62, 902−912
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Table 2. continued mi/(mol·kg−1)
mf/(mol·kg−1)
ΔdilHm/(J·mol−1)
0.0250 0.0300 0.0400 0.0450 0.0500 0.0550
0.0121 0.0148 0.0194 0.0221 0.0243 0.0269
367.42 412.47 513.03 552.21 601.50 640.21
0.0250 0.0300 0.0400 0.0450 0.0500 0.0550
0.0120 0.0143 0.0194 0.0216 0.0243 0.0265
356.43 411.65 509.51 557.22 597.41 645.62
0.0250 0.0300 0.0400 0.0450 0.0500 0.0550
0.0124 0.0147 0.0195 0.0222 0.0242 0.0270
360.88 419.73 526.48 570.43 627.30 661.55
0.0250 0.0300 0.0400 0.0450 0.0500 0.0550
0.0117 0.0141 0.0183 0.0213 0.0232 0.0260
373.26 429.08 545.92 580.91 636.08 669.08
0.0250 0.0300 0.0400 0.0450 0.0500 0.0550
0.0122 0.0144 0.0191 0.0215 0.0238 0.0264
362.75 428.10 536.21 583.24 631.75 671.37
δ/(J·mol−1) mNaCl = 0.03 −0.02 0.01 −0.01 −0.03 0.03 mNaCl = 0.02 −0.03 −0.01 0.02 0.02 0.03 mNaCl = −0.01 −0.02 −0.03 0.03 0.05 0.00 mNaCl = −0.01 −0.03 −0.02 0.04 −0.03 0.03 mNaCl = −0.02 0.01 0.02 −0.02 −0.01 0.05
mi/(mol·kg−1)
mf/(mol·kg−1)
ΔdilHm/(J·mol−1)
δ/(J·mol−1)
0.0291 0.0321 0.0345 0.0369 0.0396 0.0444
686.75 713.32 750.25 785.91 814.51 874.67
0.04 −0.02 0.01 0.04 −0.03 0.01
0.0288 0.0311 0.0333 0.0355 0.0384 0.0434
688.06 729.84 769.66 807.62 830.05 880.23
0.02 0.01 0.01 −0.02 0.01 0.02
0.0288 0.0313 0.0345 0.0366 0.0381 0.0438
718.84 756.35 774.23 816.58 867.05 902.46
−0.01 −0.03 0.02 0.04 −0.05 0.01
0.0283 0.0300 0.0330 0.0354 0.0375 0.0424
712.03 764.03 783.10 812.93 847.22 889.93
0.02 −0.02 0.03 0.02 −0.03 0.01
0.0280 0.0306 0.0332 0.0353 0.0376 0.0428
730.98 765.36 796.98 839.55 877.95 931.94
−0.03 −0.02 0.02 0.02 −0.02 0.01
−1
0.2000 mol·kg 0.0600 0.0650 0.0700 0.0750 0.0800 0.0900 0.3000 mol·kg−1 0.0600 0.0650 0.0700 0.0750 0.0800 0.0900 0.4000 mol·kg−1 0.0600 0.0650 0.0700 0.0750 0.0800 0.0900 0.5000 mol·kg−1 0.0600 0.0650 0.0700 0.0750 0.0800 0.0900 0.6000 mol·kg−1 0.0600 0.0650 0.0700 0.0750 0.0800 0.0900
mi and mf represent the initial and final molalities of PHBA and PAL, respectively; the symbol δ is defined as δ = ΔdilHm − ΔdilHm(calcd), where ΔdilHm(calcd) was calculated using eq 1 with coefficients obtained by fitting the data at the corresponding molality. Standard uncertainties u for each variable are u(T) = 0.01 K, u(P) = 10 kPa, u(mNaCl) = 0.0001 mol·kg−1, and u(mi) = 0.0001 mol·kg−1, and the relative standard uncertainty ur is ur(ΔdilHm) = 0.05. a
where HEm(mi) and HEm(mf) are the molar excess enthalpies of a solute (PAL or PHBA in this work) in the solvent (sodium chloride solutions in this work) before and after dilution, respectively. mi and mf represent the initial and final solute molalities. The calculation of ΔdilHm has been described elsewhere by us and others,37−39which is expressed as Δdil Hm = −P(1 + m i M )/m i f2
(2)
where P is the dilution thermal power of PAL or PHBA, M is the molar mass of the solute, and f 2 is the flow rate of PAL or PHBA solution. The relative mean deviation of ΔdilHm values owing to duplicate runs at each initial molality was within 1%. The final molality mf, an important parameter in data processing, can be obtained from the equation mf = m i f2 /[f1 (1 + m i M ) + f2 ]
Figure 1. Variation of the enthalpic pairwise interaction coefficients h2 of PAL (●) and PHBA (■) versus the molality m of sodium chloride solutions.
(3)
in which f1 is the flow rate of solvent. Table 2 gives the experimental ΔdilHm values of PHBA and PAL diluted from mi to mf in the aqueous sodium chloride solutions, together with the differences between the experimental values and the
corresponding calculated values. The enthalpic interaction coefficients in eq 1 obtained from the values of ΔdilHm are listed in 905
DOI: 10.1021/acs.jced.6b00458 J. Chem. Eng. Data 2017, 62, 902−912
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Table 3. Values of Density (ρ) and Apparent Molar Volumes (Vϕ) of PHBA in Aqueous Sodium Chloride Solutions at Temperatures between 293.15 and 313.15 K and Atmospheric Pressure of 0.1 MPaa 293.15 K mPHBA/ (mol·kg−1)
10−3/ −3
ρ× (kg·m )
298.15 K 10−3/ −3
Vϕ × (m3·mol )
ρ× kg·m
106/ −1
303.15 K
Vϕ × (m3·mol ) 106/ −1
10−3/ −3
308.15 K
Vϕ × (m3·mol )
ρ× kg·m
106/ −1
10−3/ −3
ρ× (kg·m )
313.15 K
Vϕ × (m3·mol ) 106/ −1
10−3/ −3
ρ× (kg·m )
Vϕ × 106/ (m3·mol−1)
mNaCl = 0.1000 mol·kg−1 0.0000
1.002423
1.001209
0.999767
0.998116
0.996272
0.0100
1.002652
99.06 ± 0.28
1.001434
99.47 ± 0.28
0.999990
99.80 ± 0.28 0.998338 100.03 ± 0.28 0.996491 100.48 ± 0.29
0.0150
1.002763
99.24 ± 0.19
1.001543
99.73 ± 0.19
1.000099
99.97 ± 0.19 0.998447 100.19 ± 0.19 0.996598 100.64 ± 0.19
0.0200
1.002872
99.41 ± 0.14
1.001652
99.81 ± 0.14
1.000206
100.13 ± 0.14 0.998554 100.35 ± 0.14 0.996704 100.79 ± 0.14
b
0.0250
1.002980
99.59 ± 0.11
1.001759
99.98 ± 0.11
1.000312
100.29 ± 0.11 0.998660 100.45 ± 0.11 0.996807 100.94 ± 0.11
0.0300
1.003084
99.83 ± 0.09
1.001863 100.15 ± 0.09
1.000417
100.41 ± 0.09 0.998762 100.66 ± 0.09 0.996911 101.05 ± 0.10
0.0350
1.003190
99.94 ± 0.08
1.001966 100.32 ± 0.08
1.000518
100.61 ± 0.08 0.998864 100.82 ± 0.08 0.997010 101.25 ± 0.08
0.0400
1.003292 100.12 ± 0.07
1.002067 100.49 ± 0.07
1.000618
100.78 ± 0.07 0.998964 100.98 ± 0.07 0.997109 101.40 ± 0.07
0.0450
1.003392 100.29 ± 0.06
1.002166 100.66 ± 0.06
1.000717
100.94 ± 0.06 0.999063 101.13 ± 0.06 0.997207 101.55 ± 0.06
0.0500
1.003491 100.47 ± 0.06
1.002263 100.83 ± 0.06
1.000814
101.10 ± 0.06 0.999160 101.29 ± 0.06 0.997303 101.71 ± 0.06
mNaCl = 0.2000 mol·kg−1 0.0000
1.006570
1.003825
1.002141
1.000267
0.0100
1.006810
97.62 ± 0.28
1.005547
1.005309 97.92 ± 0.28
1.004061
98.24 ± 0.28 1.002375
98.56 ± 0.28 1.000500
98.78 ± 0.28
0.0150
1.006927
97.82 ± 0.19
1.005663
98.12 ± 0.19
1.004175
98.43 ± 0.19 1.002489
98.75 ± 0.19 1.000614
98.96 ± 0.19
0.0200
1.007040
98.08 ± 0.14
1.005776
98.31 ± 0.14
1.004288
98.63 ± 0.14 1.002601
98.91 ± 0.14 1.000726
99.10 ± 0.14
0.0250
1.007154
98.23 ± 0.11
1.005889
98.46 ± 0.11
1.004399
98.82 ± 0.11 1.002710
99.13 ± 0.11 1.000835
99.32 ± 0.11
0.0300
1.007264
98.43 ± 0.09
1.005997
98.71 ± 0.09
1.004508
98.99 ± 0.09 1.002818
99.32 ± 0.09 1.000943
99.51 ± 0.09
0.0350
1.007372
98.63 ± 0.08
1.006104
98.91 ± 0.08
1.004614
99.21 ± 0.08 1.002924
99.51 ± 0.08 1.001049
99.69 ± 0.08 99.87 ± 0.07
0.0400
1.007478
98.84 ± 0.07
1.006210
99.11 ± 0.07
1.004719
99.39 ± 0.07 1.003028
99.70 ± 0.07 1.001153
0.0450
1.007581
99.04 ± 0.06
1.006313
99.31 ± 0.06
1.004821
99.60 ± 0.06 1.003131
99.85 ± 0.06 1.001255 100.05 ± 0.06
0.0500
1.007683
99.24 ± 0.06
1.006414
99.50 ± 0.06
1.004921
99.79 ± 0.06 1.003229 100.08 ± 0.06 1.001355 100.24 ± 0.06
mNaCl = 0.3000 mol·kg−1 0.0000
1.010635
1.007803
1.006083
1.004184
0.0100
1.010886
96.20 ± 0.28
1.009575
1.009326 96.48 ± 0.28
1.008050
96.83 ± 0.28 1.006328
97.12 ± 0.28 1.004429
97.33 ± 0.28
0.0150
1.011008
96.42 ± 0.18
1.009697
96.70 ± 0.19
1.008171
96.98 ± 0.19 1.006449
97.24 ± 0.19 1.004548
97.54 ± 0.19
0.0200
1.011129
96.60 ± 0.14
1.009816
96.90 ± 0.14
1.008288
97.26 ± 0.14 1.006565
97.54 ± 0.14 1.004665
97.71 ± 0.14
0.0250
1.011245
96.87 ± 0.11
1.009932
97.15 ± 0.11
1.008403
97.48 ± 0.11 1.006679
97.75 ± 0.11 1.004779
97.96 ± 0.11
0.0300
1.011360
97.09 ± 0.09
1.010046
97.37 ± 0.09
1.008516
97.70 ± 0.09 1.006792
97.97 ± 0.09 1.004891
98.16 ± 0.09
0.0350
1.011473
97.32 ± 0.08
1.010158
97.59 ± 0.08
1.008627
97.91 ± 0.08 1.006902
98.18 ± 0.08 1.005001
98.37 ± 0.08
0.0400
1.011583
97.54 ± 0.07
1.010268
97.78 ± 0.07
1.008737
98.09 ± 0.07 1.007010
98.39 ± 0.07 1.005109
98.58 ± 0.07
0.0450
1.011691
97.76 ± 0.06
1.010374
98.03 ± 0.06
1.008842
98.34 ± 0.06 1.007116
98.60 ± 0.06 1.005215
98.79 ± 0.06
0.0500
1.011796
97.99 ± 0.06
1.010479
98.25 ± 0.06
1.008946
98.56 ± 0.06 1.007220
98.81 ± 0.06 1.005319
98.99 ± 0.06
mNaCl = 0.4000 mol·kg−1 0.0000
1.014732
1.011817
1.010066
1.008139
0.0100
1.014996
94.70 ± 0.27
1.013640
1.013378 95.00 ± 0.28
1.012076
95.34 ± 0.28 1.010324
95.58 ± 0.28 1.008395
95.93 ± 0.28
0.0150
1.015124
94.95 ± 0.18
1.013767
95.25 ± 0.18
1.012202
95.58 ± 0.18 1.010449
95.81 ± 0.18 1.008519
96.16 ± 0.19
0.0200
1.015250
95.15 ± 0.14
1.013891
95.50 ± 0.14
1.012326
95.79 ± 0.14 1.010572
96.05 ± 0.14 1.008641
96.39 ± 0.14
0.0250
1.015371
95.46 ± 0.11
1.014011
95.79 ± 0.11
1.012446
96.06 ± 0.11 1.010692
96.29 ± 0.11 1.008761
96.59 ± 0.11
0.0300
1.015491
95.71 ± 0.09
1.014131
95.99 ± 0.09
1.012564
96.30 ± 0.09 1.010811
96.49 ± 0.09 1.008877
96.86 ± 0.09
0.0350
1.015608
95.96 ± 0.08
1.014247
96.24 ± 0.08
1.012680
96.53 ± 0.08 1.010925
96.77 ± 0.08 1.008991
97.09 ± 0.08
0.0400
1.015722
96.21 ± 0.07
1.014361
96.48 ± 0.07
1.012792
96.79 ± 0.07 1.011037
97.01 ± 0.07 1.009102
97.35 ± 0.07
0.0450
1.015834
96.46 ± 0.06
1.014472
96.73 ± 0.06
1.012903
97.03 ± 0.06 1.011147
97.24 ± 0.06 1.009213
97.56 ± 0.06
0.0500
1.015943
96.72 ± 0.06
1.014580
96.98 ± 0.06
1.013010
97.27 ± 0.06 1.011255
97.48 ± 0.06 1.009319
97.79 ± 0.06
mNaCl = 0.5000 mol·kg 1.017375
−1
0.0000
1.018778
1.015775
1.013992
1.012038
0.0100
1.019054
93.28 ± 0.27
1.017649
93.57 ± 0.27
1.016046
93.89 ± 0.27 1.014262
94.19 ± 0.28 1.012306
94.51 ± 0.28
0.0150
1.019187
93.55 ± 0.18
1.017782
93.78 ± 0.18
1.016178
94.16 ± 0.18 1.014392
94.45 ± 0.18 1.012436
94.72 ± 0.18
906
DOI: 10.1021/acs.jced.6b00458 J. Chem. Eng. Data 2017, 62, 902−912
Journal of Chemical & Engineering Data
Article
Table 3. continued 293.15 K mPHBA/ (mol·kg−1)
10−3/ −3
ρ× (kg·m )
298.15 K
Vϕ × (m3·mol ) 106/ −1
10−3/ −3
ρ× kg·m
303.15 K
Vϕ × (m3·mol ) 106/ −1
10−3/ −3
308.15 K
Vϕ × (m3·mol )
ρ× kg·m
106/ −1
10−3/ −3
ρ× (kg·m )
313.15 K
Vϕ × (m3·mol ) 106/ −1
10−3/ −3
ρ× (kg·m )
Vϕ × 106/ (m3·mol−1)
mNaCl = 0.5000 mol·kg−1 0.0200
1.019319
93.76 ± 0.14
1.017911
94.11 ± 0.14
1.016307
94.39 ± 0.14 1.014521
94.66 ± 0.14 1.012562
95.02 ± 0.14
0.0250
1.019445
94.10 ± 0.11
1.018037
94.39 ± 0.11
1.016432
94.69 ± 0.11 1.014645
94.97 ± 0.11 1.012687
95.27 ± 0.11
0.0300
1.019569
94.38 ± 0.09
1.018161
94.66 ± 0.09
1.016556
94.92 ± 0.09 1.014767
95.24 ± 0.09 1.012808
95.53 ± 0.09
0.0350
1.019691
94.65 ± 0.08
1.018281
94.93 ± 0.08
1.016675
95.22 ± 0.08 1.014886
95.50 ± 0.08 1.012927
95.78 ± 0.08
0.0400
1.019810
94.93 ± 0.07
1.018399
95.20 ± 0.07
1.016792
95.49 ± 0.07 1.015003
95.76 ± 0.07 1.013043
96.03 ± 0.07
0.0450
1.019925
95.20 ± 0.06
1.018514
95.48 ± 0.06
1.016907
95.74 ± 0.06 1.015116
96.03 ± 0.06 1.013157
96.29 ± 0.06
0.0500
1.020038
95.48 ± 0.05
1.018626
95.75 ± 0.05
1.017018
96.02 ± 0.05 1.015227
96.29 ± 0.06 1.013267
96.54 ± 0.06
mNaCl = 0.6000 mol·kg−1 0.0000
1.022598
0.0100
1.022886
1.021155 91.82 ± 0.27
1.021441
92.14 ± 0.27
1.019517
1.017705
1.015725
1.019801
92.46 ± 0.27 1.017987
92.70 ± 0.27 1.016006
92.92 ± 0.27
0.0150
1.023027
92.03 ± 0.18
1.021580
92.38 ± 0.18
1.019938
92.75 ± 0.18 1.018125
92.92 ± 0.18 1.016144
93.12 ± 0.18
0.0200
1.023162
92.42 ± 0.14
1.021714
92.73 ± 0.14
1.020072
93.04 ± 0.14 1.018258
93.25 ± 0.14 1.016276
93.48 ± 0.14
0.0250
1.023294
92.72 ± 0.11
1.021846
93.02 ± 0.11
1.020204
93.28 ± 0.11 1.018388
93.56 ± 0.11 1.016406
93.76 ± 0.11
0.0300
1.023424
93.03 ± 0.09
1.021975
93.30 ± 0.09
1.020330
93.62 ± 0.09 1.018515
93.85 ± 0.09 1.016533
94.04 ± 0.09
0.0350
1.023550
93.33 ± 0.08
1.022100
93.61 ± 0.08
1.020455
93.91 ± 0.08 1.018640
94.12 ± 0.08 1.016657
94.32 ± 0.08
0.0400
1.023673
93.63 ± 0.07
1.022223
93.90 ± 0.07
1.020576
94.20 ± 0.07 1.018761
94.42 ± 0.07 1.016779
94.60 ± 0.07
0.0450
1.023792
93.93 ± 0.06
1.022342
94.19 ± 0.06
1.020695
94.49 ± 0.06 1.018879
94.71 ± 0.06 1.016897
94.88 ± 0.06
0.0500
1.023909
94.24 ± 0.05
1.022458
94.48 ± 0.05
1.020810
94.78 ± 0.05 1.018994
94.99 ± 0.05 1.017012
95.16 ± 0.05
Standard uncertainties u for each variable are u(T) = 0.01 K. u(P) = 10 kPa, u(mNaCl) = 0.0001 mol·kg−1, and u(mPHBA) = 0.0001 mol·kg−1, and the combined expanded uncertainty Uc (level of confidence = 0.95, k = 2) is Uc(ρ) = 0.5 kg·m−3. bThe “±” symbols for Vϕ represent the 95% confidence interval. a
Table 4. Values of Density (ρ) and Apparent Molar Volumes (Vϕ) of PAL in Aqueous Sodium Chloride Solutions at Temperatures between 293.15 and 313.15 K and Atmospheric Pressure of 0.1 MPaa 293.15 K −3
ρ × 10 / mPAL/ (mol·kg−1) (kg·m−3
298.15 K
Vϕ × 10 / (m3·mol−1) 6
−3
ρ × 10 / (kg·m−3)
303.15 K
Vϕ × 10 / (m3·mol−1) 6
−3
ρ × 10 / (kg·m−3)
308.15 K
Vϕ × 10 / (m3·mol−1) 6
−3
ρ × 10 / (kg·m−3)
313.15 K −3
Vϕ × 10 / (m3·mol−1)
ρ × 10 / (kg·m−3)
6
Vϕ × 106/ (m3·mol−1)
mNaCl = 0.1000 mol·kg−1 0.0000
1.002423
0.0100
1.002788
101.44 ± 0.28b
1.001572
1.001209 101.70 ± 0.28
1.000129
0.999767 101.90 ± 0.28
0.998477
0.998116 102.07 ± 0.28
0.996633
102.23 ± 0.29
0.0250
1.003323
101.87 ± 0.11
1.002106
102.06 ± 0.11
1.000662
102.23 ± 0.11
0.999010
102.39 ± 0.11
0.997168
102.44 ± 0.11
0.0300
1.003501
101.92 ± 0.09
1.002284
102.10 ± 0.09
1.000838
102.34 ± 0.09
0.999185
102.49 ± 0.09
0.997341
102.63 ± 0.10
0.0400
1.003849
102.17 ± 0.07
1.002628
102.41 ± 0.07
1.001186
102.52 ± 0.07
0.999532
102.71 ± 0.07
0.997688
102.83 ± 0.07
0.0550
1.004361
102.53 ± 0.05
1.003139
102.76 ± 0.05
1.001695
102.89 ± 0.05
1.000041
103.06 ± 0.05
0.998200
103.13 ± 0.05
0.0650
1.004695
102.77 ± 0.04
1.003472
102.99 ± 0.04
1.002028
103.11 ± 0.04
1.000377
103.23 ± 0.04
0.998535
103.33 ± 0.04
0.0750
1.005024
103.01 ± 0.04
1.003800
103.23 ± 0.04
1.002357
103.34 ± 0.04
1.000706
103.45 ± 0.04
0.998865
103.53 ± 0.04
0.0800
1.005186
103.13 ± 0.04
1.003962
103.35 ± 0.04
1.002520
103.45 ± 0.04
1.000869
103.55 ± 0.04
0.999029
103.63 ± 0.04
0.0900
1.005507
103.37 ± 0.03
1.004281
103.58 ± 0.03
1.002841
103.67 ± 0.03
1.001191
103.76 ± 0.03
0.999353
103.83 ± 0.03
mNaCl = 0.2000 mol·kg 1.005309
0.996272
−1
0.0000
1.006570
0.0100
1.006941
100.60 ± 0.28
1.005678
100.84 ± 0.28
1.003825 1.004193
101.04 ± 0.28
1.002508
101.23 ± 0.28
1.000635
101.27 ± 0.28
0.0250
1.007486
100.96 ± 0.11
1.006220
101.26 ± 0.11
1.004733
101.45 ± 0.11
1.003048
101.63 ± 0.11
1.001178
101.57 ± 0.11
0.0300
1.007662
101.18 ± 0.09
1.006395
101.46 ± 0.09
1.004910
101.59 ± 0.09
1.003224
101.76 ± 0.09
1.001354
101.78 ± 0.09
0.0400
1.008013
101.47 ± 0.07
1.006747
101.69 ± 0.07
1.005261
101.82 ± 0.07
1.003574
102.02 ± 0.07
1.001704
102.03 ± 0.07
0.0550
1.008527
101.91 ± 0.05
1.007260
102.11 ± 0.05
1.005772
102.27 ± 0.05
1.004090
102.35 ± 0.05
1.002219
102.42 ± 0.05
0.0650
1.008861
102.20 ± 0.04
1.007593
102.39 ± 0.04
1.006105
102.55 ± 0.04
1.004420
102.67 ± 0.04
1.002555
102.67 ± 0.04
0.0750
1.009189
102.49 ± 0.04
1.007921
102.67 ± 0.04
1.006433
102.82 ± 0.04
1.004749
102.94 ± 0.04
1.002885
102.93 ± 0.04
0.0800
1.009350
102.64 ± 0.03
1.008082
102.81 ± 0.04
1.006595
102.96 ± 0.04
1.004911
103.07 ± 0.04
1.003048
103.06 ± 0.04
0.0900
1.009668
102.93 ± 0.03
1.008400
103.09 ± 0.03
1.006913
103.23 ± 0.03
1.005230
103.33 ± 0.03
1.003369
103.31 ± 0.03
907
1.002141
1.000267
DOI: 10.1021/acs.jced.6b00458 J. Chem. Eng. Data 2017, 62, 902−912
Journal of Chemical & Engineering Data
Article
Table 4. continued 293.15 K −3
ρ × 10 / mPAL/ (mol·kg−1) (kg·m−3
298.15 K
Vϕ × 10 / (m3·mol−1) 6
−3
ρ × 10 / (kg·m−3)
303.15 K
Vϕ × 10 / (m3·mol−1) 6
−3
ρ × 10 / (kg·m−3)
308.15 K
Vϕ × 10 / (m3·mol−1) 6
−3
ρ × 10 / (kg·m−3)
313.15 K −3
Vϕ × 10 / (m3·mol−1)
ρ × 10 / (kg·m−3)
6
Vϕ × 106/ (m3·mol−1)
mNaCl = 0.3000 mol·kg−1 0.0000
1.010635
0.0100
1.011012
99.69 ± 0.28
1.009326 1.009702
99.91 ± 0.28
1.007803 1.008178
100.09 ± 0.28
1.006457
1.006083 100.28 ± 0.28
1.004558
1.004184 100.40 ± 0.28
0.0250
1.011566
100.12 ± 0.11
1.010252
100.40 ± 0.11
1.008727
100.57 ± 0.11
1.007005
100.75 ± 0.11
1.005105
100.92 ± 0.11
0.0300
1.011744
100.37 ± 0.09
1.010433
100.51 ± 0.09
1.008906
100.73 ± 0.09
1.007186
100.85 ± 0.09
1.005286
101.01 ± 0.09
0.0400
1.012098
100.71 ± 0.07
1.010785
100.90 ± 0.07
1.009263
100.97 ± 0.07
1.007537
101.22 ± 0.07
1.005640
101.31 ± 0.07
0.0550
1.012615
101.22 ± 0.05
1.011301
101.40 ± 0.05
1.009776
101.54 ± 0.05
1.008054
101.68 ± 0.05
1.006158
101.76 ± 0.05
0.0650
1.012950
101.56 ± 0.04
1.011636
101.73 ± 0.04
1.010111
101.86 ± 0.04
1.008390
101.99 ± 0.04
1.006494
102.07 ± 0.04
0.0750
1.013278
101.91 ± 0.04
1.011963
102.06 ± 0.04
1.010439
102.18 ± 0.04
1.008718
102.30 ± 0.04
1.006824
102.37 ± 0.04
0.0800
1.013438
102.08 ± 0.03
1.012124
102.23 ± 0.03
1.010601
102.34 ± 0.04
1.008880
102.46 ± 0.04
1.006987
102.52 ± 0.04
0.0900
1.013754
102.42 ± 0.03
1.012440
102.56 ± 0.03
1.010918
102.66 ± 0.03
1.009198
102.77 ± 0.03
1.007306
102.82 ± 0.03
mNaCl = 0.4000 mol kg−1 0.0000
1.014732
1.013378
1.011817
1.010066
0.0100
1.015117
98.71 ± 0.27
1.013762
98.91 ± 0.28
1.012199
99.12 ± 0.28
1.010447
99.33 ± 0.28
1.008520
99.49 ± 0.28
0.0250
1.015675
99.39 ± 0.11
1.014321
99.49 ± 0.11
1.012757
99.68 ± 0.11
1.011004
99.88 ± 0.11
1.009075
100.08 ± 0.11
0.0300
1.015860
99.49 ± 0.09
1.014505
99.61 ± 0.09
1.012939
99.86 ± 0.09
1.011185
100.06 ± 0.09
1.009258
100.19 ± 0.09
0.0400
1.016218
99.88 ± 0.07
1.014860
100.06 ± 0.07
1.013298
100.19 ± 0.07
1.011542
100.42 ± 0.07
1.009615
100.54 ± 0.07
0.0550
1.016740
100.47 ± 0.05
1.015381
100.63 ± 0.05
1.013817
100.79 ± 0.05
1.012061
101.00 ± 0.05
1.010137
101.07 ± 0.05
0.0650
1.017076
100.86 ± 0.04
1.015717
101.02 ± 0.04
1.014154
101.16 ± 0.04
1.012399
101.33 ± 0.04
1.010474
101.42 ± 0.04
0.0750
1.017404
101.26 ± 0.04
1.016045
101.40 ± 0.04
1.014482
101.53 ± 0.04
1.012728
101.69 ± 0.04
1.010804
101.77 ± 0.04
0.0800
1.017564
101.45 ± 0.03
1.016206
101.59 ± 0.03
1.014643
101.72 ± 0.03
1.012889
101.87 ± 0.03
1.010966
101.95 ± 0.03
0.0900
1.017879
101.84 ± 0.03
1.016521
101.97 ± 0.03
1.014959
102.09 ± 0.03
1.013206
102.23 ± 0.03
1.011284
102.30 ± 0.03
mNaCl = 0.5000 mol·kg 1.017375
1.008139
−1
0.0000
1.018778
1.015775
1.013992
1.012038
0.0100
1.019170
97.77 ± 0.27
1.017766
97.97 ± 0.27
1.016162
98.40 ± 0.27
1.014380
98.40 ± 0.28
1.012426
98.53 ± 0.28
0.0250
1.019741
98.37 ± 0.11
1.018334
98.62 ± 0.11
1.016726
99.03 ± 0.11
1.014946
99.01 ± 0.11
1.012990
99.21 ± 0.11
0.0300
1.019924
98.66 ± 0.09
1.018516
98.91 ± 0.09
1.016909
99.25 ± 0.09
1.015130
99.22 ± 0.09
1.013176
99.33 ± 0.09
0.0400
1.020286
99.10 ± 0.07
1.018880
99.26 ± 0.07
1.017270
99.61 ± 0.07
1.015490
99.63 ± 0.07
1.013537
99.74 ± 0.07
0.0550
1.020811
99.77 ± 0.05
1.019405
99.91 ± 0.05
1.017789
100.30 ± 0.05
1.016013
100.28 ± 0.05
1.014063
100.34 ± 0.05
0.0650
1.021148
100.21 ± 0.04
1.019742
100.34 ± 0.04
1.018124
100.72 ± 0.04
1.016352
100.66 ± 0.04
1.014401
100.74 ± 0.04
0.0750
1.021475
100.66 ± 0.04
1.020070
100.77 ± 0.04
1.018450
101.14 ± 0.04
1.016681
101.07 ± 0.04
1.014731
101.15 ± 0.04
0.0800
1.021635
100.88 ± 0.03
1.020231
100.99 ± 0.03
1.018610
101.35 ± 0.03
1.016842
101.28 ± 0.03
1.014893
101.35 ± 0.03
0.0900
1.021948
101.32 ± 0.03
1.020545
101.42 ± 0.03
1.018922
101.77 ± 0.03
1.017157
101.69 ± 0.03
1.015210
101.75 ± 0.03
mNaCl = 0.6000 mol·kg−1 0.0000
1.022598
1.021155
1.019517
1.017705
1.015725
0.0100
1.022997
96.85 ± 0.27
1.021553
97.02 ± 0.27
1.019914
97.23 ± 0.27
1.018101
97.41 ± 0.27
1.016120
97.61 ± 0.27
0.0250
1.023573
97.68 ± 0.11
1.022131
97.74 ± 0.11
1.020490
97.94 ± 0.11
1.018677
98.10 ± 0.11
1.016693
98.36 ± 0.11
0.0300
1.023763
97.83 ± 0.09
1.022316
98.04 ± 0.09
1.020677
98.18 ± 0.09
1.018863
98.33 ± 0.09
1.016881
98.52 ± 0.09
0.0400
1.024129
98.33 ± 0.07
1.022684
98.46 ± 0.07
1.021044
98.60 ± 0.07
1.019229
98.79 ± 0.07
1.017246
98.98 ± 0.07
0.0550
1.024658
99.07 ± 0.05
1.023213
99.19 ± 0.05
1.021570
99.37 ± 0.05
1.019760
99.45 ± 0.05
1.017775
99.66 ± 0.05
0.0650
1.024996
99.56 ± 0.04
1.023551
99.67 ± 0.04
1.021909
99.84 ± 0.04
1.020097
99.95 ± 0.04
1.018115
100.11 ± 0.04
0.0750
1.025323
100.05 ± 0.04
1.023880
100.15 ± 0.04
1.022237
100.31 ± 0.04
1.020427
100.41 ± 0.04
1.018445
100.56 ± 0.04
0.0800
1.025483
100.30 ± 0.03
1.024040
100.39 ± 0.03
1.022398
100.55 ± 0.03
1.020588
100.64 ± 0.03
1.018606
100.79 ± 0.03
0.0900
1.025794
100.79 ± 0.03
1.024352
100.87 ± 0.03
1.022710
101.02 ± 0.03
1.020902
101.11 ± 0.03
1.018921
101.25 ± 0.03
Standard uncertainties u for each variable are u(T) = 0.01 K, u(P) = 10 kPa, u(mNaCl) = 0.0001 mol·kg−1, and u(mPAL) = 0.0001 mol·kg−1, and the combined expanded uncertainty Uc (level of confidence = 0.95, k = 2) is Uc(ρ) = 0.5 kg·m−3. bThe “±” symbols for Vϕ represent the 95% confidence interval. a
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under most conditions. In fact, the contribution of three-body and higher order interactions is small compared with that of two-body interactions. Besides, the McMillan−Mayer’s theory assumes higher order coefficients also have the contribution from h2; therefore it is difficult to interpret h3 and h4.43 3.2. Volumetric Properties. Partial molar volume is another important thermodynamic parameter to study the intermolecular interactions between solute and solvent molecules. The data of standard partial molar volume that numerically coincide with the infinite dilution apparent molar volume can be calculated from determined densities. The density data measured for PHBA + NaCl + H2O and PAL + NaCl + H2O at different temperatures are given in Tables 3 and 4, respectively. Apparent molar volumes Vϕ of PAL and PHBA in sodium chloride solutions were calculated from densities of solution (ρ) using the following equation:44
Table S1 in the Supporting Information. It is interesting to observe that the ΔdilHm value of PAL is slightly more than double the value for PHBA when diluted from the same initial molality in the aqueous sodium chloride solutions of the same molality. This is caused by the different molecular structures between PHBA and PAL. PAL molecule has an additional hydroxyl group at the C3 position of the benzene ring compared with PHBA molecule. Therefore, more energy will be needed to disrupt the hydrogen bond interactions between hydrated PAL molecules when they are diluted, resulting in a more positive ΔdilHm value of PAL than that of PHBA. The enthalpic pairwise interaction coefficients h2 reflect the summary process of interaction between two PHBA or PAL molecules in solution proceeding with the participation of the solvent molecules. The variation tendency of h2 is shown in Figure 1. From Figure 1, we can see that the values of h2 for both PHBA and PAL in pure water and aqueous sodium chloride solutions of different molalities are all negative. These results indicate that the electrostatic and hydrogen bond interactions (negative contribution to h2) are stronger than the hydrophobic−hydrophobic and hydrophobic−hydrophilic interactions (positive contribution to h2)40 as well as partial desolvation of solvation shells of solute and solvent molecules (positive contribution to h2).41 In the above interactions, the electrostatic and hydrogen bond interactions are present between solvent-mediated solute (PAL or PHBA) molecules. The hydrophobic−hydrophobic interactions occur between the benzene ring of PHBA or PAL molecules. The hydrophobic− hydrophilic interactions take place between the benzene ring of the solute molecule and the hydrophilic group of the solute molecule or solvent ion. From Table S1 (Supporting Information) and Figure 1, we know that the values of h2 become more negative with an increase in the molality of sodium chloride solutions for both PHBA and PAL. This may be explained as follows. With the increasing molality of sodium chloride solutions, the partial desolvation of solvation shells makes more positive contribution to h2. However, the negative contribution of the electrostatic and hydrogen bond interactions to h2 surpasses the positive contribution of the hydrophobic−hydrophilic interaction and partial desolvation effects, resulting in the more negative values of h2. This further verifies the dominant role of the electrostatic and hydrogen bond interactions in the examined systems. It can be clearly seen from Figure 1 that the value of h2 for PHBA is less negative than that for PAL in sodium chloride solution at the same molality. This difference is caused by the different molecular structures between PHBA and PAL. As discussed above, PAL molecule has two hydroxyl groups while PHBA molecule has only one. The stronger electrostatic interactions between the hydroxyl group of PAL molecule and solvent ions make a more negative contribution to h2. In addition, the intramolecular hydrogen bonding existing in PAL molecule will attenuate the intermolecular hydrogen bonding between them. However, the more negative value of h2 for PAL than that for PHBA suggests that the intermolecular hydrogen bonding and electrostatic interactions are dominant over the intramolecular hydrogen bonding. This indicates that the molecular structure of drugs has an important influence on the intermolecular interaction and the efficacy of the drugs.42 As for enthalpic triplet and quartet interaction coefficients (h3 and h4), the values of them listed in Table S1 (Supporting Information) are irregular although the values of h3 are positive
Vϕ = M /ρ − 1000(ρ − ρ0 )/(mρρ0 )
(4)
in which M is the molar mass of PAL or PHBA, m is its molality, and ρ0 is the density of the solvent (NaCl + H2O). The values of the calculated apparent molar volumes of PAL and PHBA are also given in Tables 3 and 4, respectively. From Tables 3 and 4, we can see that the apparent molar volumes increase with the ascent of temperature and the increasing molalities of PAL and PHBA. The standard partial molar volume V0ϕ was calculated by correlating Vϕ with m using eq 5:28
Figure 2. Variation of apparent molar volumes (Vϕ) of PHBA (a) and PAL (b) versus their molalities at 298.15 K in the aqueous sodium chloride solutions of different molalities (0.1 (■), 0.2 (●), 0.3 (▲), 0.4 (▼), 0.5 (◀), and 0.6 mol·kg−1 (Δ)). 909
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Vϕ = V ϕ0 + S Vm
Article
(5)
where SV is obtained from the slope of the straight line. Figure 2 shows the variation of apparent molar volumes (Vϕ) of PHBA and PAL versus their molalities in the aqueous sodium chloride solutions of different molalities at 298.15 K. The corresponding plots at 293.15, 303.15, 308.15, and 313.15 K are provided in Figures S1−S4 in the Supporting Information, respectively. All of the plots of Vϕ versus m showed a good linear relation (R2 > 0.99). The values of V0ϕ and SV of PAL and PHBA are summarized in Table S2 in the Supporting Information, and the change tendencies of V0ϕ and SV with increasing sodium chloride concentration are shown in Figures 3 and 4, respectively. The
Figure 4. Variation of experimental slope (SV) of PHBA (a) and PAL (b) versus the molality m of sodium chloride in aqueous solutions at T = 293.15 (■), 298.15 (●), 303.15 (▲), 308.15 (▼), and 313.15 K (◀).
both PAL and PHBA, while the change trend in the values of V0ϕ is contrary. The rising temperature may facilitate the partial desolvation of solvation shells of solute and solvent species. The release of some water molecules from the hydrophilic solvation layer around solvent molecules into the bulk of the solvent may be responsible for the increase of V0ϕ. In contrast, the release of some water molecules from the hydrophobic hydration shells of solute molecules will lead to a negative contribution to SV. From Figures 3 and 4 we can see that the values of V0ϕ decrease with the increase of salt concentration, while the change trend in the values of SV is contrary. This phenomenon might be mainly caused by interaction of PAL or PHBA molecule with the coexisting ions.36 With the elevation of the molality of sodium chloride, the degree of disruption of the hydration shells of solvent ions is intensified, resulting in tighter hydration layers around solute molecules. Therefore, the dipole−dipole and hydrogen bond interactions between solvated solute molecules release more water molecules into the bulk medium, making a positive contribution to SV. At the same time, the disruption effect attenuates the electrostatic and hydrogen bond interactions between solute and solvent molecules, resulting in the decrease of V0ϕ. It can also be seen from Table S2 (Supporting Information) that the values of V0ϕ and SV of PAL are slightly larger and smaller than those of PHBA in sodium chloride solution at the same molality, respectively. This is also caused by the structure difference between PHBA and PAL. On one side, the stronger solute−solvent electrostatic and hydrogen bond interactions between PAL molecule and solvent ion increase the values of
Figure 3. Variation of standard partial molar volume (V0ϕ) of PHBA (a) and PAL (b) versus the molality m of sodium chloride in aqueous solutions at T = 293.15 (■), 298.15 (●), 303.15 (▲), 308.15 (▼), and 313.15 K (◀).
values of V0ϕ and SV show the nature of (solute + solvent) and (solute + solute) interactions, respectively. It can be seen from Table S2 (Supporting Information) that the values of V0ϕ and SV are all positive. The positive V0ϕ indicates that (solute + solvent) electrostatic and hydrogen bond interactions (positive contribution to V0ϕ) surpass hydrophobic−hydrophilic interactions (negative contribution to V0ϕ).29 The positive SV may be interpreted from the fact that dipole−dipole and hydrogen bond interactions between solute molecules themselves (positive contribution to SV) surpass hydrophobic−hydrophobic and hydrophobic−hydrophilic interactions between them. This conclusion agrees well with the effect of different interactions on enthalpic interaction coefficient h2. The data in Table S2 (Supporting Information) also show that the values of SV decrease with a rise in temperature for 910
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V0ϕ. On the other side, the stronger hydrophilic−hydrophobic interactions between PAL molecules decrease the values of SV.
(2) Dai, J.; Mumper, R. J. Plant phenolics: extraction, analysis and their antioxidant and anticancer properties. Molecules 2010, 15, 7313− 7352. (3) Bendary, E.; Francis, R. R.; Ali, H. M. G.; Sarwat, M. I.; El Hady, S. Antioxidant and structure−activity relationships (SARs) of some phenolic and anilines compounds. Ann. Agric. Sci. 2013, 58, 173−181. (4) Castellano, G.; Tena, J.; Torrens, F. Classification of phenolic compounds by chemical structural indicators and its relation to antioxidant properties of Posidonia oceanica (L.) delile. MATCH Commun. Math. Comput. Chem. 2012, 67, 231−250. (5) Zhou, Z.; Zhang, Y.; Ding, X. R.; Chen, S. H.; Yang, J.; Wang, X. J.; Jia, G. L.; Chen, H. S.; Bo, X. C.; Wang, S. Q. Protocatechuic aldehyde inhibits hepatitis B virus replication both in vitro and in vivo. Antiviral Res. 2007, 74, 59−64. (6) Etoh, H.; Murakami, K.; Yogoh, T.; Ishikawa, H.; Fukuyama, Y.; Tanaka, H. Anti-oxidative compounds in barley tea. Biosci., Biotechnol., Biochem. 2004, 68, 2616−2618. (7) Lee, B. H.; Yoon, S. H.; Kim, Y. S.; Kim, S. K.; Moon, B. J.; Bae, Y. S. Apoptotic cell death through inhibition of protein kinase CKII activity by 3,4-dihydroxybenzaldehyde purified from xanthium strumarium. Nat. Prod. Res. 2008, 22, 1441−1450. (8) Kim, K. J.; Kim, M. A.; Jung, J. H. Antitumor and antioxidant activity of protocatechualdehyde produced from streptomyces lincolnensis M-20. Arch. Pharmacal Res. 2008, 31, 1572−1577. (9) Chang, Z. Q.; Gebru, E.; Lee, S. P.; Rhee, M. H.; Kim, J. C.; Cheng, H.; Park, S. C. In vitro antioxidant and anti-inflammatory activities of protocatechualdehyde isolated from phellinus gilvus. J. Nutr. Sci. Vitaminol. 2011, 57, 118−122. (10) Zhou, Z.; Liu, Y.; Miao, A. D.; Wang, S. Q. Protocatechuic aldehyde suppresses TNF-α-induced ICAM-1 and VCAM-1 expression in human umbilical vein endothelial cells. Eur. J. Pharmacol. 2005, 513, 1−8. (11) Lee, J. R.; Lee, M. H.; Eo, H. J.; Park, G. H.; Song, H. M.; Kim, M. K.; Lee, J. W.; Jeong, J. B. The contribution of activating transcription factor 3 to apoptosis of human colorectal cancer cells by protocatechualdehyde, a naturally occurring phenolic compound. Arch. Biochem. Biophys. 2014, 564, 203−210. (12) Jeong, J. B.; Lee, S. H. Protocatechualdehyde possesses anticancer activity through downregulating cyclin D1 and HDAC2 in human colorectal cancer cells. Biochem. Biophys. Res. Commun. 2013, 430, 381−386. (13) Tao, Y. H.; Yuan, Z.; Tang, X. Q.; Xu, H. B.; Yang, X. L. Inhibition of GABA shunt enzymes’ activity by 4-hydroxybenzaldehyde derivatives. Bioorg. Med. Chem. Lett. 2006, 16, 592−595. (14) Alvarado, I. E.; Lomascolo, A.; Navarro, D.; Delattre, M.; Asther, M.; Lesage-Meessen, L. Evidence of a new biotransformation pathway of p-coumaric acid into p-hydroxybenzaldehyde in Pycnoporus cinnabarinus. Appl. Microbiol. Biotechnol. 2001, 57, 725−730. (15) Zhang, Q. L.; Liu, Y. Z.; Li, G. M.; Li, J. P. Preparation of p-hydroxybenzaldehyde by hydrolysis of diazonium salts using rotating packed bed. Chin. J. Chem. Eng. 2011, 19, 140−144. (16) Jin, J. S.; Sang, J. R.; Fan, X.; Chang, C. W.; Wu, H. Solubilities of hydroxybenzaldehyde isomers and their mixture in subcritical 1,1,1,2-tetrafluoroethane. Thermochim. Acta 2016, 624, 8−14. (17) Bountagkidou, O. G.; Ordoudi, S. A.; Tsimidou, M. Z. Structure−antioxidant activity relationship study of natural hydroxybenzaldehydes using in vitro assays. Food Res. Int. 2010, 43, 2014− 2019. (18) Ha, J. H.; Lee, D. U.; Lee, J. T.; Kim, J. S.; Yong, C. S.; Kim, J. A.; Ha, J. S.; Huh, K. 4-Hydroxybenzaldehyde from gastrodia elata B1. is active in the antioxidation and GABAergic neuromodulation of the rat brain. J. Ethnopharmacol. 2000, 73, 329−333. (19) Wu, H.; Zhu, J.; Wang, Y. W.; Chang, C. W.; Jin, J. S. Measurement and modeling for solubility of 3-hydroxybenzaldehyde and its mixture with 4-hydroxybenzaldehyde in supercritical carbon dioxide. Fluid Phase Equilib. 2016, 409, 271−279. (20) Jin, J. S.; Wang, Y. W.; Zhang, H. F.; Fan, X.; Wu, H. Solubility of 4-hydroxybenzaldehyde in supercritical carbon dioxide with and without cosolvents. J. Chem. Eng. Data 2014, 59, 1521−1527.
4. CONCLUSIONS The enthalpies of dilution of PAL and PHBA in aqueous sodium chloride solutions at 298.15 K and the densities of the ternary homogeneous systems at different temperatures (293.15, 298.15, 303.15, 308.15, and 313.15 K) have been determined. The enthalpic interaction coefficients (h2, h3, and h4), apparent molar volumes (Vϕ), standard partial molar volumes (V0ϕ), and experimental slope (SV) for the investigated systems have been obtained from the experimental data. The following conclusions can be drawn from the above results and discussion. (1) The enthalpic pairwise interaction coefficients h2 of PAL and PHBA in aqueous sodium chloride solutions are all negative and decrease with the increase in the molality of sodium chloride. (2) The value of h2 for PHBA is less negative than that for PAL at the same sodium chloride molality. (3) The values of V0ϕ and SV of PAL and PHBA are all positive and have different variation trends with the increasing temperature and molality of sodium chloride. (4) The value of V0ϕ of PAL is larger than that of PHBA in aqueous sodium chloride solutions at the same molality, while the value of SV is contrary. (5) The thermodynamic difference between PAL and PHBA is caused by their different molecular structures, especially the number of hydroxyl groups.
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ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jced.6b00458. Apparent molar volumes at different temperatures (Figures S1−S4), enthalpic interaction coefficients (Table S1), and standard partial molar volumes and experimental slope (Table S2) (PDF)
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Fax: +86-635-8239136. ORCID
Min Liu: 0000-0002-1918-9072 Funding
This work was supported by the National Natural Science Foundation of China (Grant No. 21473085), the Key Research and Development Program of Shandong Province of China (Grant No. 2015GGB01567), and the Tai-Shan Scholar Research Fund of Shandong Province of China. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This work was technically supported by Shandong Collaborative Innovation Center for Antibody Drugs and Engineering Research Center for Nanomedicine and Drug Delivery Systems.
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