- Email: [email protected]
Solubility and thermodynamic properties of vanillyl alcohol in some pure solvents
Accepted Manuscript Solubility and thermodynamic properties of vanillyl alcohol in some pure solvents Yanmei Guo, Yunhui Hao, Yanan Zhou, Zhengyang Han, Chuang Xie, Weiyi Su, Hongxun Hao PII: DOI: Reference:
S0021-9614(16)30395-0 http://dx.doi.org/10.1016/j.jct.2016.11.030 YJCHT 4909
To appear in:
J. Chem. Thermodynamics
Received Date: Revised Date: Accepted Date:
8 October 2016 23 November 2016 27 November 2016
Please cite this article as: Y. Guo, Y. Hao, Y. Zhou, Z. Han, C. Xie, W. Su, H. Hao, Solubility and thermodynamic properties of vanillyl alcohol in some pure solvents, J. Chem. Thermodynamics (2016), doi: http://dx.doi.org/ 10.1016/j.jct.2016.11.030
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Solubility and thermodynamic properties of vanillyl alcohol in some pure solvents Yanmei Guo
a,b
Weiyi Su c,
Hongxun Haoa,b,*
a
, Yunhui Hao
a,b
, Yanan Zhou
a,b
, Zhengyang Hana,b, Chuang Xie
a,b
,
National Engineering Research Centre of Industrial Crystallization Technology,
School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China b
Collaborative Innovation Center of Chemical Science and Engineering(Tianjin),
Tianjin 300072, China c School of Chemical Engineering, Hebei University of Technology, Tianjin 300132, China
ABSTRACT In this work, the solubility of vanillyl alcohol in eight pure solvents was measured by using a static gravimetric method over the temperature range from 293.15 K to 343.15 K. It was found that the solubility of vanillyl alcohol in ethanol is the highest while solubility in butyl acetate is the least among all the selected solvents. The solubility values increase with the temperature rise. The capability of vanillyl alcohol to form hydrogen bond with solvents was applied to explain the difference of solubility in these selected pure solvents. Furthermore, the modified Apelblat equation, the λh equation and the Wilson equation were used to correlate the experimental solubility. Finally, the thermodynamic properties of vanillyl alcohol in different pure solvents were investigated and are discussed based on the Wilson equation and the experimental solubility date. Keywords:
Vanillyl
thermodynamic properties.
alcohol;
Solubility;
Hydrogen
bond;
Dissolution
1. Introduction Vanillyl alcohol(C8H10O3,CAS registry NO.498-00-0, shown in figure 1), an extract of Gastrodia elata Blume [1], is known as one of the most important precursor for synthesizing vanillin [2]. It has been know that vanillyl alcohol possesses pharmacological activity, including anti-convulsive effect, anti-angiogenic effect, anti-nociceptive effect and anti-inflammatory effect, which indicates its plausible therapeutic effect in some medicines [3,4]. Due to the good bioactivity and favourable pharmacokinetic characteristics of vanillyl alcohol, it is widely used for treating for some neurodegenerative diseases such as Parkinson’s disease [5]. Reports about vanillyl alcohol mainly concentrated on the extraction process and application process, except that Wang et al. [6] obtained the single-crystal data and structure by the steps of synthesis, column chromatography and recrystallization. Little attention was paid to the crystallization and purification of vanillyl alcohol. In pharmaceutical industry, the crystallization process is a significant separation and purification process for a crystalline compound and could deeply affect the purity and morphology of product [7]. In order to design precisely and optimize the crystallization process of vanillyl alcohol, it is vital to obtain the thermodynamic properties of vanillyl alcohol in different solvents. However, the literature regarding the solubility and thermodynamic properties of vanillyl alcohol is rare. In this study, the experimental solubility of vanillyl alcohol in eight organic solvents including ethanol, 2-propanol, 1-buanol, 1-pentanol, 3-methyl-1-butanol, methyl cyanide, ethyl acetate and butyl acetate over the temperature range from 293.15 K to 343.15 K was measured by using a static gravimetric method [8,9].The modified Apelblat equation, the λh equation and the Wilson equation were used to correlate the experimental solubility result [8-10]. Finally, the dissolution enthalpy and entropy and the Gibbs energy change of vanillyl alcohol in all the eight pure solvents were calculated and analysed based on the experimental solubility and the Wilson model [11].
2. Experimental 2.1. Materials Vanillyl alcohol with a purity (as mass fraction) of 0.995 was supplied by Jiangxi Zhengtong chemical Co. Ltd of China, which was used without further purification. The ethanol, 2-propanol, 1-buanol, 1-pentanol, 3-methyl-1-butanol, methyl cyanide, ethyl acetate and butyl acetate were purchased from Tianjin Jiangtian Chemical Reagent Co. Ltd. of China. All of the selected organic solvents were analytical grade reagents and were used without further purification. The mass fraction purity of these solvents is higher than 0.997, which was confirmed by gas chromatography. More details about the chemicals used in this work are displayed in table 1. 2.2. X-ray powder diffraction The X-ray powder diffraction (XRPD) was used to identify the crystal form of vanillyl alcohol before and after each experiment. The XRPD spectra were obtained by using D/MAX 2500 diffractometer (Cu Kα radiation, λKα=0.15405 nm) over a diffraction angle(2θ) range of 2° to 50°, at a scanning rate of 0.067°·s-1. 2.3. Differential scanning calorimetry (DSC) measurements The analyses of the melting temperature Tm and enthalpy of fusion ∆fusH of vanillyl alcohol were performed on DSC 1/500, Mettler-Toledo, Switzerland. Indium (Tm = 429.75 K, ∆fusH = 28.45 J·g-1) and n-dodecane (Tm = 263.5K, ∆fusH= 216.73J·g-1) were used to calibrate the device and an empty pan was used as reference. A total of about (5-10) mg sample of vanillyl alcohol was added into an aluminium pan and accurately measured by an analytical balance (Mettler Toledo AB204-N, Switzerland) with an uncertainty of ±0.0001 g. Then the aluminium pan was heated from 298.15 K to 433.15 K at a heating rate of 5 K·min-1 under the protection of a nitrogen atmosphere. 2.4. Solubility measurement The solubility of vanillyl alcohol in different pure solvents was determined by using the gravimetric method [11-14]. A known amount of solvent and excess amount of vanillyl alcohol were added into a 100 mL water-jacketed glass vessel. And in
order to ensure proper mixing, a magnetic stirrer was used. The temperature of the glass vessel was controlled by a thermostat (CF41, Julabo, Germany) with accuracy of±0.01 K. At the given temperature, the solid-liquid mixtures in the glass vessel were stirred continuously for 8 hours to make sure that the solid-liquid equilibrium was reached. And then, the agitation was turned off and the suspension was kept static at the same temperature for 3 hours. It is worth noting that when the temperature is higher than 323.15K, a condenser was used to protect the solvent from volatilizing too quickly. After that, about 5 mL of the upper clean solution was withdrawn from the glass vessel quickly using a syringe and then filtered into a pre-weighted glass vial by organic membranes (0.2µm, Tianjin Legg Technology Co. Ltd). All the syringes and organic membranes were pre-heated or pre-cooled. Especially, when the experiment temperature is above 323.15 K i.e. (323.15 K, 333.15 K, 343.15 K) in ethanol, 2-propanol, ethyl acetate and methyl cyanide, the upper clean solution was filtered into the glass vial very quickly, then a piece of plastic wrap was used to cover the glass vial immediately to prevent the solution from volatilizing. The glass vial containing the upper clean solution was weighted at once and placed into a vacuum oven at the temperature of 333.15 K after weighing. The weight of this glass vial was measured every 4 hours and the reading was recorded until the differences between three measurements were less than 0.0010g. In order to make sure that the drying phase did not solvate, the thermo-gravimetric (TG) curves for all drying samples were determined. It was found that all the samples (including raw material) started to decompose or lose weight above Td=433.0 K which is much higher than the melting temperature Tm=389.0 K. One typical pattern is shown in figure 2. These TG results verify that no solvate existed in the drying phase. During the measuring process of solubility, all the weighing was obtained by an electronic analytic balance (ML204, Mettler Toledo, Switzerland) with the uncertainty of ±0.0001 g. Each process was repeated three times and the average value was used to calculate the mole fraction solubility of vanillyl alcohol.
The mole fraction solubility (x1) of vanillyl alcohol in different pure solvents can be calculated by the following equation [15]:
x1 =
m1 / M 1 m1 / M1 + m2 / M 2
(1)
where m1 and m2 are the mass of vanillyl alcohol and solvent, respectively. M1 and M2 represent the molar mass of vanillyl alcohol and solvent.
3. Thermodynamic models
3.1. Modified Apelblat equation The modified Apelblat equation is a semi-empirical equation, which has been widely used to correlate and predict the solubility of various materials [16-18]:
ln(x1 ) = A +
B + C ln(T (K)) T (K )
(2)
where x1 is the mole fraction solubility of solute; T refers to the absolute temperature; A, B and C represent empirical parameters of this equation. The values of A and B stand for the variation of activity coefficient in real solution; C reflects the effect of temperature on fusion enthalpy. 3.2.λh equation The λh equation was first presented by Buchowski et al., which can be used to describe the solid-liquid equilibrium of this work. The equation can be expressed as follows [19]:
ln(1 + λ
1 1 1 − x1 ) = λ h( − ) x1 T Tm
(3)
where Tm is the melting temperature of vanillyl alcohol. λ and h refer to equation parameters, both of which can be obtained by the fitting of experimental values. The value of λ represents the non-ideality of the solution system. The value of h describes the enthalpy of the solution [18]. 3.3. Local composition models
On the basis of solid–liquid phase equilibrium theory, the correlation between solubility and absolute temperature can be described as the following local composition equation [20]:
ln( x1 ) = − ln γ 1 +
∆ fus H 1 1 1 ( − )− R Tm T RT
∫
T
Tm
∆CP1dT +
1 T ∆CP1 dT R ∫Tm T
(4)
In this equation, γ1 stands for the activity coefficient, ∆fusH and Tm are the enthalpy of fusion and the melting point of solute, respectively; R represents the gas constant; ∆CP1 refers to the difference of the molar heat capacity between melting state of the
solute and solid state of the solute. Considering that ∆CP1 is relatively less important in the equation, it can be ignored. Generally the thermodynamic model can be further simplified as follows[21]:
ln x1 =
∆ fus H 1 1 ( − ) − ln γ 1 R Tm T
(5)
This simplified equation is widely used for correlating the solubility of many materials. In order to use this equation, the melting temperature and enthalpy of fusion of solute should be measured in advance. At the same time, an appropriate model for calculating the activity coefficient of the solute in the liquid phase should be chosen. In this work, the Wilson model was selected to calculate the activity coefficient of vanillyl alcohol. 3.4. Wilson model The activity coefficient of the solute can be determined by the following Wilson model [22].
ln γ 1 = − ln( x1 + Λ12 x2 ) + x2 (
Λ12 Λ 21 ) − x1 + Λ12 x2 x2 + Λ 21 x1
(6)
ln γ 2 = − ln( x2 + Λ21x1 ) + x1 (
Λ21 Λ12 ) − x2 + Λ21x1 x1 + Λ12 x2
(7)
Where Λ12 and Λ21 can be calculated as follows:
ν2 λ −λ ν ∆λ exp(− 12 11 ) = 2 exp(− 12 ) RT RT ν1 ν1 ν λ −λ ν ∆λ Λ 21 = 1 exp(− 11 12 ) = 1 exp(− 21 ) RT RT ν2 ν2 Λ12 =
(8)
here ∆λ12and ∆λ21 represent the cross interaction energy whose value can be obtained by fitting experimental results for the solid-liquid equilibrium, ν1 and ν2 stand for the molar volume of the solute and solvent, which can be calculated by their density and mole mass. The density of the selected solvents can be found from the literature [23] and the density of vanillyl alcohol was measured by a tapping apparatus (ZS-201, Liaoning Instrumentation Research Institute Co. Ltd) with the experiment error of ±0.5%. The details to get the density of vanillyl alcohol are as follows: Pre-weighted solute was put into a 25 mL graduated cylinder. Then, the graduated cylinder was placed at the fixed position of the instrument. After setting the vibration frequency (150 times·min-1) and time （ 40 min), the vibration process was started. In the vibration process, the air between the particles is squeezed out and the particles are arranged in order. Until the volume of sample in the graduated cylinder remained constant, the vibration was stopped. This process was repeated three times and the average value was used to calculate the molar volume of vanillyl alcohol. The molar volume of vanillyl alcohol (v1) can be calculated by the following equation: v1 =
V ×M m
(9)
here V is the sample volume measured by graduated cylinder, m is the weight of sample in graduated cylinder; M is the mole mass of solute. The molar volume of chemicals, including vanillyl alcohol and eight organic solvents used in this work, are listed in table 2.
4. Results and discussion
4.1. XRPD/DSC analysis The X-ray powder diffraction (XRPD) pattern of vanillyl alcohol before and after solubility experiments was measured. No change of PXRD results was found. The
PXRD results for the raw material and the solid phase after solubility experiments are shown in figure 3 and 4. It can be concluded that the crystal forms of vanillyl alcohol remained constant during the experimental process. The values of the melting temperature and fusion enthalpy of vanillyl alcohol were measured by using DSC. The results are shown in figure 5. It can be seen that the melting temperature of vanillyl alcohol determined as the mean extrapolated onset temperature is (389.0±0.5) K and it is in agreement with the literature values Tm=(387.15-388.15) K [24], Tm=(387.65-388.65) K [25] and Tm=(386.5-389.5) K [26]. The slight deviations between our results and reported results might be caused by different measuring instruments and different measuring conditions. The molar fusion enthalpy of vanillyl alcohol is 30.74 kJ·mol-1. The standard uncertainty of melting temperature is 0.5 K, while the relative standard uncertainty of fusion enthalpy is approximately 0.02. 4.2. Solubility of vanillyl alcohol in pure solvents The experimental solubility results of vanillyl alcohol in eight pure solvents at different temperatures are listed in table 3 and depicted in figure 6. From table 3 and figure6, it can be seen that the solubility of vanillyl alcohol in all the selected pure solvents increases with increasing temperature. At a given temperature, except methyl cyanide, the solubility in these selected pure solvents can be ranked as ethanol ＞ 2-propanol ＞ 1-butanol ＞ 1-pentanol ＞ 3-methyl-1-butanol ＞ ethyl acetate ＞ butyl
acetate. Generally, the solubility of the solute in different solvents follows the “like dissolves like” principle which indicates that the order of solubility in the solvents selected should be consistent with the polarity. It is well known that the dielectric constant is a key index of polarity. However, according to the dielectric constant(D) [23], the sequence of polarity should be: methyl cyanide(D=35.7)＞ ethanol(D=25.7) ＞ 2-propanol(D=18.3) ＞ 1-butanol(D=17.3) ＞ 3-methyl-1-butanol(D=14.7) ＞
1-pentanol(D=13.9)＞ethyl acetate(D=6.02)＞butyl acetate(D=5.01). It can be seen that the solubility of vanillyl alcohol does not strictly follow the order of polarity of solvents. It can be explained be the fact that dissolution is a complicated process and
polarity is not the unique factor to affect it. A similar phenomenon has been reported in other compounds, such as DMU [10], and FM [12]. From the structural formula of vanillyl alcohol, it can be seen that the solute molecule has not only a hydrogen bonding acceptor but also a hydrogen bonding donor, which suggests that a hydrogen bond can be formed between the solute and solvent molecules. Thus, in this system, it can be expected that both the van der Waals interaction and hydrogen bond will play an important role in the dissolution process of vanilly alcohol. Gu et al. [27] used statistical analysis method to obtained the values of hydrogen bond donor property (α) and hydrogen bond acceptor property(β). For the selected solvents in this work, the rank of the summation of hydrogen bond donor properties are ethanol= 1-butanol= 1-pentanol＞2-propanol＞methyl cyanide＞ethyl acetate=butyl acetate and the rank of the summation of hydrogen bond acceptor properties are 2-propanol＞ethanol= 1-butanol= 1-pentanol＞ethyl acetate=butyl acetate＞methyl cyanide, respectively. The dielectric constant and the summation of hydrogen bond donor properties and hydrogen bond acceptor properties are depicted in figure7. In conclusion, even though the polarity of methyl cyanide is the highest, its capability for forming a hydrogen bond with vanillyl alcohol is weak, which could result in lower solubility of vanillyl alcohol. In addition, although the polarity of 3-methyl-1-butanol is a little higher than 1-butanol, the steric hindrance of 3-methyl-1 butanol is greater than 1-butanol. As a result, the solubility of vanillyl alcohol in 1-butanol is a greater than is the solubility in 3-methyl-1 butanol. To extend the application range of these solubility results, three thermodynamic models, including the modified Apelblat equation, the λh equation and the Wilson model, were applied to correlate the experimental solubility results. The calculated solubility of vanillyl alcohol in all the selected solvents by the three models is listed in table 3. Parameters of these models were obtained by fitting the experimental values in Matlab and the results are shown in table 4-6. The root-mean-square deviations (RMSD) and average relative deviation (ARD%) are applied to assess the correlation results [28]:
1
1 RMSD = N
cal 2 x1,exp i − x1, i ( ) ∑ exp x1,i i =1 N
(10)
cal exp 100 N x1,i − x1,i ARD% = ∑ xexp N i =1 1,i
cal
where xi
exp
and xi
(11)
stand for the calculated solubility and the experimental
solubility values, respectively. The N represents the number of the experimental points. The calculated results of RMSD, ARD are also listed in table 3. It can be clearly seen from table 3 that the Apelblat models gives better fitting results with all the ARD% values lower than 5%, which suggests that the experimental and the correlated results determined by Apelblat model equation are in good agreement at all tested temperatures. 4.3. Dissolution thermodynamic properties In this study, for the vanillyl alcohol-solvent system, the dissolution process can be assumed to consist of four energetic steps (heating, fusion, cooling and mixing processes) in theory. Then the Gibbs energy of dissolution (∆disG), the enthalpy of dissolution (∆disH) and the entropy of dissolution (∆disS) can be calculated by the following equation: ∆disM = x(∆heatM + ∆fusM + ∆coolM) + ∆mixM
(12)
where M can be replaced by G, H, and S; x represents the mole fraction solubility of vanillyl alcohol; ∆heatM and ∆coolM stand for the thermodynamic properties of heating and cooling process, respectively. The ∆fusM is the fusion thermodynamic properties; ∆mixM represents the mixing properties. For the heating and cooling process, it is reasonable to assume that the difference of heat capacity of solid state vanillyl alcohol and the heat capacity of liquid state vanillyl alcohol(∆CP)is approximated by the entropy of fusion, calculated as ∆CP≈∆fusS = ∆fusH/Tm [29,30], and the thermodynamic properties can be determined
by the following equations: ∆(heat + cool)H = ∆Cp(Tm – T)
ln(Tm/T)
(13) (14)
heat)G
= ∆(cool + heat)H - /T ∆(cool + heat)S
(15)
(15)
Besides, during the phase transition of solute, the system is in equilibrium, so ∆fusG=0.
The mixing properties of vanillyl alcohol including ∆mixG, ∆mixS, and ∆mixH, could be determined by: ∆mixG =
GE + ∆mixGid
(16)
∆mixH =
HE + ∆mixHid
(17)
∆mixG =
SE + ∆mixSid
(18)
where GE,HE and SE represent the excess Gibbs energy, excess enthalpy and excess entropy, respectively, and ∆mixGid, ∆mixHid, ∆mixSid stand for mixing Gibbs energy, mixing enthalpy and mixing entropy of the ideal solution, respectively. For an ideal solution system, the mixing properties can be defined by the following equation: ∆mixGid = RT(x1lnx1 + x2lnx2)
(19)
∆mixSid = R(x1lnx1 + x2lnx2)
(20)
∆mixHid = 0
(21)
where x1 and x2 stand for the mole fraction of solute and solvent in solution, respectively. According to the Wilson model, the excess mixing properties can be deduced by the following equations [16]:
GE = RT (x1 ln γ 1 + x2 ln γ 2 )
(22)
where γ1 and γ2 refer to the activity coefficient of solute and solvent in the real solution. Their values are listed in table 7. In this work, based on equations (6-8), GE, HE and SE in the binary system can be defined by the following equations:
GE = − RT [ x1 ln( x1 + x2 Λ12 ) + x2 ln( x2 + x1Λ 21 )]
(23)
∆λ Λ ∆λ21Λ 21 ∂(GE / T ) ) = x1 x2 ( 12 12 + H E = −T 2 x1 + Λ12 x2 x2 + Λ21 x1 ∂T SE =
H E − GE T
(24) (25)
In order to know the contributions of enthalpy and entropy to the dissolution process, %ζH (the relative contribution of enthalpy) and %ζTS(the relative contribution od entropy) were calculated by the following equations [31,32]:
%ζ H = 100 ×
∆H d ∆H d + T ∆Sd
(26)
%ζ TS = 100 ×
T ∆Sd ∆H d + T ∆S d
(27)
According to the experimental solubility values and the fitted Wilson model parameters, the values of ∆disG, ∆disS, and ∆disH can be calculated. The results are shown in table 7.The relative contributions of enthalpy and entropy to the dissolution process in the eight pure solvents are also listed in table 7. It can be seen from table7 that the values of ∆disG are negative, which indicates the dissolution process in all the selected solvents is spontaneous. It is known that lower values of ∆disG leads to greater solubility. The values of ∆disG obtained in this work decrease with the increase ng of temperature, which is consistent with the trend of solubility within the tested temperature range. Besides, the values of ∆disS and ∆disH are all positive, which suggests that the dissolution process in all selected solvents is entropy-driven and endothermic. In all cases, the values of %ζH are lower than 49.6 and the values of %ζTS are higher than 50.4. It can be concluded that the main contributor to ∆disG is entropy, which is consistent with the results that the dissolution process is entropy-driven. 5. Conclusions
In this study, the gravimetric method was applied to measure the solubility of vanillyl alcohol in eight pure solvents, including ethanol, 2-propanol, 1-butanol, 1-pentanol, 3-methyl-1butanol, methyl cyanide, ethyl acetate, and butyl acetate in the temperature ranges from 293.15K to 343.15K at atmospheric pressure. It was found
that the solubility of vanillyl alcohol in ethanol is the highest while the solubility in butyl acetate is the least among all the selected solvents. The solubility values increase with the temperature rise. The experimental solubility values for vanillyl alcohol in the above mentioned pure solvents were well correlated and analysed by using the modified Apelblat equation, the λh equation and the Wilson equation. The correlated results show that the modified Apelblat equation provides better correlation results. Furthermore, based on the Wilson equation, the dissolution thermodynamic properties, including enthalpy, entropy and Gibbs energy were calculated. At all temperatures studied, the enthalpy and entropy increase with the increasing temperature. On the contrary, the Gibbs energy decreases with rising temperature. The results indicate that the dissolution process in all the tested solvents is spontaneous and entropy-driven.
Author information Corresponding Author
*Tel: 86-22-27405754. Fax: 86-22-27314971 E-mail: [email protected] Notes
The authors declare no competing financial interest.
Acknowledgements
This research is financially supported by The Natural Science Foundation of Hebei Province (B2015202090) and Major National Scientific Instrument Development Project (No.21527812)..
References
[1] I.S. Kim, D.K. Choi, H.J. Jung, Molecules 16 (2011) 5349-5361.
[2] R.H.H.V.D. Heuvel, M.W. Fraaije, C. Laane, W.J.H.V. Berkel, J. Agric. Food. Chem.49 (2001) 2954-2958. [3] H.J. Jung, Y.S. Song, C.J. Lim, E.H. Park, Arch. Pharmacal Res. 31 (2008) 1275-1279. [4] C.L. Hsieh, C.H. Chang, S.Y. Chiang, T.C. Li, N.Y. Tang, C.Z. Pon, C.T. Hsieh, J.G. Lin, Life Sci 67 (2000) 1185-1195. [5] Hsu L C, Wen Z H, Lee K Y. US20090258951[P]. 2009. [6] Q. Wang, S.P. Li, Acta Crystallogr. Sect. E: Struct. Rep. Online 65 (2009) o2838. [7] J. Li, W. Zhao, B. Ying, J. Wang, Ind. Eng. Chem. Res. 52 (2013) 3019-3026. [8] X. Huang, J. Wang, H. Hao, J. Ouyang, Y. Gao, Y. Bao, Y. Wang, Q. Yin, Fluid Phase Equilib. 394 (2015) 148-155. [9] C. Wang, Y. Wang, Q. Yin, Z. Xu, Y. Bao, B. Hou, W. Liu, H. Hao, J. Chem. Eng. Data 60 (2015) 3053-3061. [10]P. Zhu, Y. Chen, M. Zhang, Y. Bao, C. Xie, B. Hou, J. Gong, W. Chen, J. Chem. Thermodyn. (2016) 9–16. [11]G. Wang, Y. Wang, Y. Ma, H. Hao, Q. Luan, H. Wang, J. Chem. Thermodyn. 77 (2014) 144–150. [12]Y. Qin, H. Wang, P. Yang, S. Du, C. Huang, Y. Du, S. Wu, J. Gong, Q. Yin, Fluid Phase Equilib.403 (2015) 145-152. [13]J. Yang, H. Wu, Y. Wang, Q. Luan, J. Zhang, G. Wang, H. Hao, J. Chem. Thermodyn. 83 (2015) 77–84. [14]J. Ouyang, J. Wang, X. Huang, Y. Bao, Y. Wang, Q. Yin, A. Liu, X. Li, H. Hao, J. Chem. Thermodyn. 91 (2015) 73-79. [15]E.M. Gonçalves, M.E.M.D. Piedade, J. Chem. Thermodyn. 47 (2012) 362-371. [16]A. Apelblat, E. Manzurola, J. Chem. Thermodyn. 31 (1999) 85-91. [17]R.V. Orye, J.M. Prausnitz, Ind. Eng. Chem. Res. 57 (1965) 18-26. [18]J. Chen, Z.X. Zeng, W.L. Xue, D. Wang, Y. Huang, Ind. Eng. Chem. Res. 50 (2011) 11755-11762. [19]H. Buchowski, A. Ksiazczak, S. Pietrzyk, J. Phys. Chem. 84 (1980) 975-979. [20]H. Yan, Z. Wang, J. Wang, Ind. Eng. Chem. Res. 51 (2012) 2808-2813. [21]H. Renon, J.M. Prausnitz, AlChE J. 14 (1968) 135–144. [22]G.M. Wilson, J. Am. Chem. Soc. 86 (1964). [23] Smallwood,I.M, Wiley: New York,1996. [24] Goethals, G, Natuurwetenschappelijk Tijdschrift (Ghent) 18,(1936), 249-55. [25] Pearl, Irwin A, J. Org. Chem. 12,(1947),79-84. [26] Barnes, R. A, An. Acad. Bras. Cienc. 52,(1980),515-20. [27]C.H. Gu, H. Li, R.B. Gandhi, K. Raghavan, Int. J. Pharm 283 (2004) 117-125.
[28]J. Wang, C. Xie, Q. Yin, L. Tao, J. Lv, Y. Wang, F. He, H. Hao, J. Chem. Thermodyn. 95 (2016) 63-71. [29] Neau, S. H., G. L. Flynn, Pharm. Res. 7(1990):1157-62. [30] J.Yan, Q. Yin, C.Jiang, J. Gong, M. Zhang, Y. Wang, B. Hou, H. Hao, Fluid Phase Equilib. 406(2015):77-90. [31]D.R. Delgado, F. Martínez, Fluid Phase Equilib. 360 (2013) 88-96. [32]W. Tang, C. Xie, Z. Wang, S. Wu, Y. Feng, X. Wang, J. Wang, J. Gong, Fluid Phase Equilib. 363 (2014) 86-96.
Table headings: Table 1
The sources and mass fraction purity of the materials used in this paper. a,b Table 2
Molar volumes of vanillyl alcohol and all the organic solvents used. Table 3
Experimental and correlated mole fraction solubility of vaillyl alcohol in selected solvents over the temperature range from 293.15 K to 343.15 K (p = 101.3 kPa ).a ,b ,c Table 4
The parameters of the modified Apelblat equation for vanillyl alcohol in different pure solvents. a Table 5
The parameters of the λh equation for vanillyl alcohol in different pure solvents. a Table 6
The parameters of the Wilson equation for vanillyl alcohol in different pure solvents. a
Table 7
The dissolution thermodynamic properties of vanillyl alcohol in eight pure solvents. a
Figure captions: Figure1. Chemical structure (a) and three-dimensional structure (b) of vanillyl alcohol Figure2. The thermo-gravimetric (TG) curves for each drying phase at the experimental temperature of 303.15K for different solvents. The TG patterns from bottom to top in this diagram are raw material and the patterns of drying phase in ethanol; 2-propanol; 1-butanol; 1-pentanol; 3-methyl-butanol; methyl cyanide; ethyl acetate; butyl acetate, respectively.
Figure3. X-ray powder diffraction pattern of vanillyl alcohol Figure4. The schematic diagram of the XRPD patterns for the solid phases after solubility experiments for different solvents. The XRPD patterns from bottom to top in this schematic diagram are raw material and the patterns of solid phase in ethanol; 2-propanol; 1-butanol; 1-pentanol; 3-methyl-butanol; methyl cyanide; ethyl acetate; butyl acetate, respectively. Figure5. DSC plot of vanillyl alcohol Figure6. Experimental solubility values for vanillyl alcohol in pure organic solvents:(■)ethanol;(◄)2-propanol;(●)1-butanol;(▲)1-pentanol;(▼)3-methyl-bu tanol;(▶ ▶)methyl cyanide;(★ ★)ethyl acetate;(◆ ◆)butyl acetate.The solid lines are correlated values based on the Modified Apelblat model. Figure7. The dielectric constant, summation of hydrogen bond donor properties and hydrogen bond acceptor properties of each solvent
Table 1
The sources and mass fraction purity of the materials used in this paper. a, b Substance Vanillyl alcohol Ethanol 2-Propanol 1-Butanol 1-pentanol 3-methyl-1-buta nol Methyl cyanide Ethyl acetate 1-Buthyl acetate
Source Jiangxi zhengtong Chemical Co., Ltd, China Tianjin Jiangtian Chemical Co., Ltd, China Tianjin Jiangtian Chemical Co., Ltd, China Tianjin Jiangtian Chemical Co., Ltd, China Tianjin Jiangtian Chemical Co., Ltd, China Tianjin Jiangtian Chemical Co., Ltd, China Tianjin Jiangtian Chemical Co., Ltd, China Tianjin Jiangtian Chemical Co., Ltd, China Tianjin Jiangtian Chemical Co., Ltd, China
Mass fraction purity
Purification method
Analysis method
≥0.995
None
HPLCa
﹥0.997
None
GCb
﹥0.997
None
GCb
﹥0.997
None
GCb
﹥0.997
None
GCb
﹥0.997
None
GCb
﹥0.997
None
GCb
﹥0.997
None
GCb
﹥0.997
None
GCb
a
High-performance liquid chromatography, which was carried out by Jiangxi
zhengtong Chemical Co., Ltd, China b
Gas chromatography, which was carried out by Tianjin Jiangtian Chemical Co.,
Ltd, China
Table 2
Molar volumes of vanillyl alcohol and all the organic solvents used. substance
Vanillyl alcohola
Ethanolb
2-Propanolb
V/(cm3·mol-1)
282.7
58.37
76.43 b
1-Butanolb
1-pentanolb
91.53
108.2
substance
3-methyl-1butanolb
Methyl cyanideb
Ethyl acetate
1-Buthyl acetateb
V(cm3·mol-1)
108.9
52.48
97.83
131.9
a
The molar volume of vanillyl alcohol was calculated by Eqs (9).
b
The molar volume of each solvent (T=293.15K)was obtained from reference[23].
Table 3
Experimental and correlated mole fraction solubility of vaillyl alcohol in selected solvents over the temperature range from 293.15 K to 343.15 K (p = 101.3 kPa ).a ,b ,c
T/K 293.15 303.15 313.15 323.15 333.15 343.15 ARDb
102x1exp,a 4.42 6.27 9.36 14.2 20.5 31.7
102RMSDb 293.15 303.15 313.15 323.15 333.15 343.15 ARDb
2.84 4.18 5.78 9.57 14.9 23.7
102RMSDb 293.15 303.15 313.15 323.15 333.15 343.15 ARDb
2.34 3.93 5.38 9.02 13.4 18.2
102RMSDb 293.15 303.15 313.15 323.15 333.15 343.15 ARDb
2.14 3.38 4.90 7.28 10.2 15.5
102RMSDb 293.15 303.15 313.15 323.15
2.25 3.02 4.47 6.52
102x1Apel
102x1λh
102x1Wilson
4.14 6.48 9.83 14.5 20.8 29.1 4.45
3.57 5.90 9.50 14.7 21.6 30.1 6.84
0.183 2-Propanol 2.76 4.06 6.13 9.45 14.9 23.7 2.29
1.10
0.901
2.60 4.17 6.50 9.88 14.7 21.4 6.03
2.37 3.84 6.07 9.69 15.2 23.5 5.59
0.167 1-Butanol 2.18 3.69 5.91 9.01 13.1 18.4 4.34
1.00
0.301
2.36 3.74 5.77 8.71 12.9 18.8 3.93
2.57 3.93 5.86 8.73 12.8 18.6 4.78
1.30 1-Pentanol 2.28 3.31 4.84 7.10 10.5 15.4 2.57
0.385
0.378
2.17 3.3 4.93 7.23 10.1 15.2 1.64
2.14 3.26 4.87 7.19 10.5 15.4 1.46
0.149
0.139
2.13 3.15 4.57 6.55
1.97 2.98 4.44 6.52
Ethanol 4.44 6.38 9.33 13.9 20.8 31.6 1.02
0.152 3-Methyl-1-Butanol 2.27 3.11 4.39 6.34
333.15 343.15 ARDb
9.12 14.0
102RMSDb 293.15 303.15 313.15 323.15 333.15 343.15 ARDb
1.72 2.62 4.15 7.13 12.7 22.0
102RMSDb 293.15 303.15 313.15 323.15 333.15 343.15 ARDb
1.76 2.96 3.93 6.82 10.0 16.3
102RMSDb 293.15 303.15 313.15 323.15 333.15 343.15 ARDb
0.980 1.77 2.70 4.28 6.53 10.7
102RMSDb
a
9.34 14.0 1.87
9.34 13.3 3.25
9.45 13.9 3.27
0.129 Methyl cyanide 1.60 2.58 4.28 7.26 12.5 22.0 2.51
0.320
0.193
1.51 2.69 4.62 7.67 12.3 19.2 8.37
1.46 2.47 4.19 7.26 12.8 21.9 4.14
0.120 Ethyl Acetate 1.86 2.76 4.20 6.51 10.2 16.3 4.27
1.19
0.144
1.72 2.78 4.38 6.75 10.2 15.3 4.87
1.69 2.71 4.20 6.63 10.2 16.2 4.06
0.208 Butyl Acetate 1.10 1.70 2.66 4.19 6.67 10.7 3.76
0.482
0.192
1.00 1.67 2.72 4.32 6.74 10.4 2.57
1.05 1.70 2.68 4.23 6.62 10.7 2.46
0.906
0.148
0.0604
xexp is the experimentally solubility; xApel, xλh and xWilson represent the calculated
mole fraction solubility correlated by the modified Apelblat equation, λh equation,and Wislon model, respectively. b
ARD and RMSD are the average relative deviation and root-mean-square deviations,
respectively, they are calculated based on Eqs.(10)-(11). c
Standard uncertainty of temperature is u(T)=0.005 K. The standard uncertainty of
pressure is u(p)=0.3kPa. The relative standard uncertainty of solubility is ur(x1)=0.05.
Table 4
The parameters of the modified Apelblat equation for vanillyl alcohol in different pure solvents. a solvent Ethanol 2-Propanol 1-Butanol 1-Pentanol 3-Methyl-1-Butanol Methyl cyanide Ethyl Acetate Butyl Acetate a b
Modified Apelblat equation Aa/102 Ba/103 -2.519±0.6461 8.339±3.098 -3.127±0.8910 10.85±4.285 1.546±1.777 -11.03±8.543 -1.825±1.061 5.149±5.086 -2.941±0.9673 10.53±4.630 -3.543±0.9128 11.98±4.4097 -2.893±1.627 9.703±7.823 -2.419±1.138 7.282±5.478
Ca/10 3.880±0.9521 4.490±1.313 -2.127±2.617 2.837±1.563 4.479±1.425 5.444±1.343 4.440±2.397 3.741±1.676
A, B and C are the parameters of the modified Apelblat equation. The number in the right side of “±” means the standard error of each coefficient in
different solvent. (0.95 level of confidence) . Table 5
The parameters of the λh equation for vanillyl alcohol in different pure solvents. a
λh equation
solvent
λa/102
ha/102
Ethanol 2-Propanol 1-Butanol 1-Pentanol 3-Methyl-1-Butanol Methyl cyanide Ethyl Acetate Butyl Acetate
122.2±19.78 87.36±19.88 69.29±8.634 41.22±2.462 31.87±3.694 116.0±30.07 58.42±9.891 42.45±3.261
32.89±3.454 47.93±7.154 58.19±4.693 85.77±2.823 102.6±6.920 44.52±8.202 72.05±8.009 105.4±5.446
a
λ and h are the parameters of the λh equation.
b
The number in the right side of “±” means the standard error of each coefficient in
different solvent. (0.95 level of confidence)
Table 6
The parameters of the Wilson equation for vanillyl alcohol in different pure solvents. a
Wilson equation solvent
∆λ12/kJ·mol-1a
∆λ21/kJ· mol-1a
Ethanol 2-Propanol 1-Butanol 1-Pentanol 3-Methyl-1-Butanol Methyl cyanide Ethyl Acetate Butyl Acetate
0.1459±1.681 -0.6483±0.5030 -2.709±0.6080 -1.998±0.2258 -2.204±0.3177 -0.1240±0.2128 -0.7321±0.3693 0.6640±0.1638
1.851±0.4024 2.493±0.2402 4.721±0.9181 4.989±0.5115 6.170±0.9334 3.293±0.06717 0.3310±0.3168 3.342±0.1868
a
∆λ12 and ∆λ21 are the parameters of the Wilson equation.
b
The number in the right side of “±” means the standard error of each coefficient in
different solvent. (0.95 level of confidence)
Table 7
The dissolution thermodynamic properties of vanillyl alcohol in eight pure solvents. a
T/K
∆disG a /(kJ·mol-1)
∆disH a /(kJ·mol-1)
∆disS a /(J·K-1·mol-1)
%ζHb
%ζTSb
γ1c
γ2c
6.48 8.82 12.6 18.0 24.7 35.6
49.6 49.2 49.0 48.8 48.6 48.7
50.4 50.8 51.0 51.2 51.4 51.3
1.25 1.15 1.05 0.98 0.939 0.932
1.00 1.01 1.01 1.01 1.01 1.01
4.04 5.73 7.62
49.5 49.2 48.8
50.5 50.8 51.2
1.89 1.76 1.65
1.00 1.00 1.00
Ethanol
293.2 303.2 313.2 323.2 333.2 343.2
-0.365 -0.506 -0.718 -1.01 -1.34 -1.76
1.87 2.59 3.78 5.55 7.80 11.6
293.2 303.2 313.2
-0.239 -0.339 -0.454
1.16 1.68 2.28
2-Propanol
323.2 333.2 343.2
-0.677 -0.949 -1.30
3.69 5.63 8.67
12.0 17.8 26.5
48.8 48.7 48.8
51.2 51.3 51.2
1.49 1.34 1.2
1.01 1.02 1.04
3.14 5.02 6.62 10.5 15.0 19.6
49.0 48.9 48.6 48.7 48.7 48.5
51.0 51.1 51.4 51.3 51.3 51.5
1.74 1.72 1.71 1.65 1.58 1.51
1.00 1.00 1.00 1.00 1.01 1.02
0.810 2.87 1.26 4.32 1.80 6.01 2.62 8.55 3.38 10.8 5.46 16.9 3-Methyl-1-butanol 0.840 2.95 1.11 3.82 1.62 5.42 2.31 7.57 3.18 10.2 4.81 14.9 Methyl cyanide 0.730 2.55 1.10 3.74 1.71 5.69 2.89 9.31 5.02 15.7 8.36 25.4 Ethyl acetate 0.710 2.48 1.16 3.97 1.52 5.10 2.59 8.40 3.73 11.8 5.94 18.2 Butyl acetate 0.400 1.41 0.710 2.42 1.06 3.54
49.2 49.1 48.8 48.7 48.4 48.6
50.8 50.9 51.2 51.3 51.6 51.4
2.09 2.08 2.05 2.01 1.94 1.83
1.00 1.00 1.00 1.00 1.01 1.02
49.3 48.9 48.8 48.6 48.4 48.5
50.7 51.1 51.2 51.4 51.6 51.5
2.27 2.27 2.25 2.21 2.15 2.03
1.00 1.00 1.00 1.00 1.01 1.01
49.5 49.2 49.0 49.0 49.0 49.0
50.5 50.8 51.0 51.0 51.0 51.0
3.07 2.74 2.39 1.99 1.59 1.29
1.00 1.00 1.01 1.01 1.03 1.07
49.2 49.2 48.8 48.8 48.7 48.7
50.8 50.8 51.2 51.2 51.3 51.3
2.64 2.5 2.38 2.18 1.99 1.73
1.00 1.00 1.00 1.01 1.01 1.03
49.1 49.1 48.9
50.9 50.9 51.1
4.26 3.99 3.73
1.00 1.00 1.00
1-Butanol
293.2 303.2 313.2 323.2 333.2 343.2
-0.215 -0.330 -0.434 -0.641 -0.855 -1.06
0.880 1.46 1.96 3.24 4.74 6.33 1-Pentanol
293.2 303.2 313.2 323.2 333.2 343.2
-0.189 -0.278 -0.379 -0.518 -0.644 -0.894
293.2 303.2 313.2 323.2 333.2 343.2
-0.194 -0.253 -0.350 -0.471 -0.608 -0.810
293.2 303.2 313.2 323.2 333.2 343.2
-0.145 -0.212 -0.317 -0.494 -0.774 -1.15
293.2 303.2 313.2 323.2 333.2 343.2
-0.155 -0.241 -0.313 -0.480 -0.648 -0.907
293.2 303.2 313.2
-0.0890 -0.146 -0.210
323.2 333.2 343.2
-0.305 -0.423 -0.601
1.65 2.47 3.95
5.36 7.81 12.1
a
∆disG, ∆disS and ∆disG are calculated based on Eqs (12)-(25).
b
%ζH and %ζTS are calculated by Eqs (26)-(27).
c
48.8 48.7 48.7
51.2 51.3 51.3
γ1 andγ2 are calculated by Eqs (6)-(8).
d
The combined expanded uncertainties U are Uc(∆disG)=0.060∆disG; Uc(∆disH)=0.055 ∆disH; Uc(∆disS)=0.060∆disS . (0.95 level of confidence).
Figure1.Chemical structure (a) and three-dimensional structure (b) of vanillyl alcohol
3.41 3.07 2.63
1.00 1.01 1.02
Figure2 The thermo-gravimetric (TG) curves for each drying phase at the experiment temperature of 303.15K for different solvents. The TG patterns from bottom to top in this diagram are raw material and the patterns of drying phase in ethanol; 2-propanol; 1-butanol; 1-pentanol; 3-methyl-butanol; methyl cyanide; ethyl acetate; butyl acetate, respectively.
Figure3. X-ray powder diffraction pattern of vanillyl alcohol
Figure4. The schematic diagram of the XRPD patterns for all the solid phase after solubility experiments for different solvents. The XRPD patterns from bottom to top in this schematic diagram are raw material and the patterns of solid phase in ethanol; 2-propanol; 1-butanol; 1-pentanol; 3-methyl-butanol; methyl cyanide; ethyl acetate; butyl acetate, respectively.
Figure 5. DSC plot of vanillyl alcohol
Figure6. Experimental solubility values for vanillyl alcohol in pure organic solvents:(■)ethanol;(◄)2-propanol;(●)1-butanol;(▲)1-pentanol;(▼)3-methyl-bu tanol;(▶ ▶)methyl cyanide;(★ ★)ethyl acetate;(◆ ◆) butyl acetate. The solid lines are correlated values based on the Modified Apelblat model.
Figure7. The dielectric constant, summation of hydrogen bond donor properties and hydrogen bond acceptor properties of each solvent
The solubilities of vanillyl alcohol in eight pure solvents were determined by
using a static gravimetric method. The capability of vanillyl alcohol to form hydrogen bond with solvents was
applied to explain the difference of solubility in different solvents. Dissolution thermodynamic properties of vanillyl alcohol were calculated and
discussed.
S0021-9614(16)30395-0 http://dx.doi.org/10.1016/j.jct.2016.11.030 YJCHT 4909
To appear in:
J. Chem. Thermodynamics
Received Date: Revised Date: Accepted Date:
8 October 2016 23 November 2016 27 November 2016
Please cite this article as: Y. Guo, Y. Hao, Y. Zhou, Z. Han, C. Xie, W. Su, H. Hao, Solubility and thermodynamic properties of vanillyl alcohol in some pure solvents, J. Chem. Thermodynamics (2016), doi: http://dx.doi.org/ 10.1016/j.jct.2016.11.030
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Solubility and thermodynamic properties of vanillyl alcohol in some pure solvents Yanmei Guo
a,b
Weiyi Su c,
Hongxun Haoa,b,*
a
, Yunhui Hao
a,b
, Yanan Zhou
a,b
, Zhengyang Hana,b, Chuang Xie
a,b
,
National Engineering Research Centre of Industrial Crystallization Technology,
School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China b
Collaborative Innovation Center of Chemical Science and Engineering(Tianjin),
Tianjin 300072, China c School of Chemical Engineering, Hebei University of Technology, Tianjin 300132, China
ABSTRACT In this work, the solubility of vanillyl alcohol in eight pure solvents was measured by using a static gravimetric method over the temperature range from 293.15 K to 343.15 K. It was found that the solubility of vanillyl alcohol in ethanol is the highest while solubility in butyl acetate is the least among all the selected solvents. The solubility values increase with the temperature rise. The capability of vanillyl alcohol to form hydrogen bond with solvents was applied to explain the difference of solubility in these selected pure solvents. Furthermore, the modified Apelblat equation, the λh equation and the Wilson equation were used to correlate the experimental solubility. Finally, the thermodynamic properties of vanillyl alcohol in different pure solvents were investigated and are discussed based on the Wilson equation and the experimental solubility date. Keywords:
Vanillyl
thermodynamic properties.
alcohol;
Solubility;
Hydrogen
bond;
Dissolution
1. Introduction Vanillyl alcohol(C8H10O3,CAS registry NO.498-00-0, shown in figure 1), an extract of Gastrodia elata Blume [1], is known as one of the most important precursor for synthesizing vanillin [2]. It has been know that vanillyl alcohol possesses pharmacological activity, including anti-convulsive effect, anti-angiogenic effect, anti-nociceptive effect and anti-inflammatory effect, which indicates its plausible therapeutic effect in some medicines [3,4]. Due to the good bioactivity and favourable pharmacokinetic characteristics of vanillyl alcohol, it is widely used for treating for some neurodegenerative diseases such as Parkinson’s disease [5]. Reports about vanillyl alcohol mainly concentrated on the extraction process and application process, except that Wang et al. [6] obtained the single-crystal data and structure by the steps of synthesis, column chromatography and recrystallization. Little attention was paid to the crystallization and purification of vanillyl alcohol. In pharmaceutical industry, the crystallization process is a significant separation and purification process for a crystalline compound and could deeply affect the purity and morphology of product [7]. In order to design precisely and optimize the crystallization process of vanillyl alcohol, it is vital to obtain the thermodynamic properties of vanillyl alcohol in different solvents. However, the literature regarding the solubility and thermodynamic properties of vanillyl alcohol is rare. In this study, the experimental solubility of vanillyl alcohol in eight organic solvents including ethanol, 2-propanol, 1-buanol, 1-pentanol, 3-methyl-1-butanol, methyl cyanide, ethyl acetate and butyl acetate over the temperature range from 293.15 K to 343.15 K was measured by using a static gravimetric method [8,9].The modified Apelblat equation, the λh equation and the Wilson equation were used to correlate the experimental solubility result [8-10]. Finally, the dissolution enthalpy and entropy and the Gibbs energy change of vanillyl alcohol in all the eight pure solvents were calculated and analysed based on the experimental solubility and the Wilson model [11].
2. Experimental 2.1. Materials Vanillyl alcohol with a purity (as mass fraction) of 0.995 was supplied by Jiangxi Zhengtong chemical Co. Ltd of China, which was used without further purification. The ethanol, 2-propanol, 1-buanol, 1-pentanol, 3-methyl-1-butanol, methyl cyanide, ethyl acetate and butyl acetate were purchased from Tianjin Jiangtian Chemical Reagent Co. Ltd. of China. All of the selected organic solvents were analytical grade reagents and were used without further purification. The mass fraction purity of these solvents is higher than 0.997, which was confirmed by gas chromatography. More details about the chemicals used in this work are displayed in table 1. 2.2. X-ray powder diffraction The X-ray powder diffraction (XRPD) was used to identify the crystal form of vanillyl alcohol before and after each experiment. The XRPD spectra were obtained by using D/MAX 2500 diffractometer (Cu Kα radiation, λKα=0.15405 nm) over a diffraction angle(2θ) range of 2° to 50°, at a scanning rate of 0.067°·s-1. 2.3. Differential scanning calorimetry (DSC) measurements The analyses of the melting temperature Tm and enthalpy of fusion ∆fusH of vanillyl alcohol were performed on DSC 1/500, Mettler-Toledo, Switzerland. Indium (Tm = 429.75 K, ∆fusH = 28.45 J·g-1) and n-dodecane (Tm = 263.5K, ∆fusH= 216.73J·g-1) were used to calibrate the device and an empty pan was used as reference. A total of about (5-10) mg sample of vanillyl alcohol was added into an aluminium pan and accurately measured by an analytical balance (Mettler Toledo AB204-N, Switzerland) with an uncertainty of ±0.0001 g. Then the aluminium pan was heated from 298.15 K to 433.15 K at a heating rate of 5 K·min-1 under the protection of a nitrogen atmosphere. 2.4. Solubility measurement The solubility of vanillyl alcohol in different pure solvents was determined by using the gravimetric method [11-14]. A known amount of solvent and excess amount of vanillyl alcohol were added into a 100 mL water-jacketed glass vessel. And in
order to ensure proper mixing, a magnetic stirrer was used. The temperature of the glass vessel was controlled by a thermostat (CF41, Julabo, Germany) with accuracy of±0.01 K. At the given temperature, the solid-liquid mixtures in the glass vessel were stirred continuously for 8 hours to make sure that the solid-liquid equilibrium was reached. And then, the agitation was turned off and the suspension was kept static at the same temperature for 3 hours. It is worth noting that when the temperature is higher than 323.15K, a condenser was used to protect the solvent from volatilizing too quickly. After that, about 5 mL of the upper clean solution was withdrawn from the glass vessel quickly using a syringe and then filtered into a pre-weighted glass vial by organic membranes (0.2µm, Tianjin Legg Technology Co. Ltd). All the syringes and organic membranes were pre-heated or pre-cooled. Especially, when the experiment temperature is above 323.15 K i.e. (323.15 K, 333.15 K, 343.15 K) in ethanol, 2-propanol, ethyl acetate and methyl cyanide, the upper clean solution was filtered into the glass vial very quickly, then a piece of plastic wrap was used to cover the glass vial immediately to prevent the solution from volatilizing. The glass vial containing the upper clean solution was weighted at once and placed into a vacuum oven at the temperature of 333.15 K after weighing. The weight of this glass vial was measured every 4 hours and the reading was recorded until the differences between three measurements were less than 0.0010g. In order to make sure that the drying phase did not solvate, the thermo-gravimetric (TG) curves for all drying samples were determined. It was found that all the samples (including raw material) started to decompose or lose weight above Td=433.0 K which is much higher than the melting temperature Tm=389.0 K. One typical pattern is shown in figure 2. These TG results verify that no solvate existed in the drying phase. During the measuring process of solubility, all the weighing was obtained by an electronic analytic balance (ML204, Mettler Toledo, Switzerland) with the uncertainty of ±0.0001 g. Each process was repeated three times and the average value was used to calculate the mole fraction solubility of vanillyl alcohol.
The mole fraction solubility (x1) of vanillyl alcohol in different pure solvents can be calculated by the following equation [15]:
x1 =
m1 / M 1 m1 / M1 + m2 / M 2
(1)
where m1 and m2 are the mass of vanillyl alcohol and solvent, respectively. M1 and M2 represent the molar mass of vanillyl alcohol and solvent.
3. Thermodynamic models
3.1. Modified Apelblat equation The modified Apelblat equation is a semi-empirical equation, which has been widely used to correlate and predict the solubility of various materials [16-18]:
ln(x1 ) = A +
B + C ln(T (K)) T (K )
(2)
where x1 is the mole fraction solubility of solute; T refers to the absolute temperature; A, B and C represent empirical parameters of this equation. The values of A and B stand for the variation of activity coefficient in real solution; C reflects the effect of temperature on fusion enthalpy. 3.2.λh equation The λh equation was first presented by Buchowski et al., which can be used to describe the solid-liquid equilibrium of this work. The equation can be expressed as follows [19]:
ln(1 + λ
1 1 1 − x1 ) = λ h( − ) x1 T Tm
(3)
where Tm is the melting temperature of vanillyl alcohol. λ and h refer to equation parameters, both of which can be obtained by the fitting of experimental values. The value of λ represents the non-ideality of the solution system. The value of h describes the enthalpy of the solution [18]. 3.3. Local composition models
On the basis of solid–liquid phase equilibrium theory, the correlation between solubility and absolute temperature can be described as the following local composition equation [20]:
ln( x1 ) = − ln γ 1 +
∆ fus H 1 1 1 ( − )− R Tm T RT
∫
T
Tm
∆CP1dT +
1 T ∆CP1 dT R ∫Tm T
(4)
In this equation, γ1 stands for the activity coefficient, ∆fusH and Tm are the enthalpy of fusion and the melting point of solute, respectively; R represents the gas constant; ∆CP1 refers to the difference of the molar heat capacity between melting state of the
solute and solid state of the solute. Considering that ∆CP1 is relatively less important in the equation, it can be ignored. Generally the thermodynamic model can be further simplified as follows[21]:
ln x1 =
∆ fus H 1 1 ( − ) − ln γ 1 R Tm T
(5)
This simplified equation is widely used for correlating the solubility of many materials. In order to use this equation, the melting temperature and enthalpy of fusion of solute should be measured in advance. At the same time, an appropriate model for calculating the activity coefficient of the solute in the liquid phase should be chosen. In this work, the Wilson model was selected to calculate the activity coefficient of vanillyl alcohol. 3.4. Wilson model The activity coefficient of the solute can be determined by the following Wilson model [22].
ln γ 1 = − ln( x1 + Λ12 x2 ) + x2 (
Λ12 Λ 21 ) − x1 + Λ12 x2 x2 + Λ 21 x1
(6)
ln γ 2 = − ln( x2 + Λ21x1 ) + x1 (
Λ21 Λ12 ) − x2 + Λ21x1 x1 + Λ12 x2
(7)
Where Λ12 and Λ21 can be calculated as follows:
ν2 λ −λ ν ∆λ exp(− 12 11 ) = 2 exp(− 12 ) RT RT ν1 ν1 ν λ −λ ν ∆λ Λ 21 = 1 exp(− 11 12 ) = 1 exp(− 21 ) RT RT ν2 ν2 Λ12 =
(8)
here ∆λ12and ∆λ21 represent the cross interaction energy whose value can be obtained by fitting experimental results for the solid-liquid equilibrium, ν1 and ν2 stand for the molar volume of the solute and solvent, which can be calculated by their density and mole mass. The density of the selected solvents can be found from the literature [23] and the density of vanillyl alcohol was measured by a tapping apparatus (ZS-201, Liaoning Instrumentation Research Institute Co. Ltd) with the experiment error of ±0.5%. The details to get the density of vanillyl alcohol are as follows: Pre-weighted solute was put into a 25 mL graduated cylinder. Then, the graduated cylinder was placed at the fixed position of the instrument. After setting the vibration frequency (150 times·min-1) and time （ 40 min), the vibration process was started. In the vibration process, the air between the particles is squeezed out and the particles are arranged in order. Until the volume of sample in the graduated cylinder remained constant, the vibration was stopped. This process was repeated three times and the average value was used to calculate the molar volume of vanillyl alcohol. The molar volume of vanillyl alcohol (v1) can be calculated by the following equation: v1 =
V ×M m
(9)
here V is the sample volume measured by graduated cylinder, m is the weight of sample in graduated cylinder; M is the mole mass of solute. The molar volume of chemicals, including vanillyl alcohol and eight organic solvents used in this work, are listed in table 2.
4. Results and discussion
4.1. XRPD/DSC analysis The X-ray powder diffraction (XRPD) pattern of vanillyl alcohol before and after solubility experiments was measured. No change of PXRD results was found. The
PXRD results for the raw material and the solid phase after solubility experiments are shown in figure 3 and 4. It can be concluded that the crystal forms of vanillyl alcohol remained constant during the experimental process. The values of the melting temperature and fusion enthalpy of vanillyl alcohol were measured by using DSC. The results are shown in figure 5. It can be seen that the melting temperature of vanillyl alcohol determined as the mean extrapolated onset temperature is (389.0±0.5) K and it is in agreement with the literature values Tm=(387.15-388.15) K [24], Tm=(387.65-388.65) K [25] and Tm=(386.5-389.5) K [26]. The slight deviations between our results and reported results might be caused by different measuring instruments and different measuring conditions. The molar fusion enthalpy of vanillyl alcohol is 30.74 kJ·mol-1. The standard uncertainty of melting temperature is 0.5 K, while the relative standard uncertainty of fusion enthalpy is approximately 0.02. 4.2. Solubility of vanillyl alcohol in pure solvents The experimental solubility results of vanillyl alcohol in eight pure solvents at different temperatures are listed in table 3 and depicted in figure 6. From table 3 and figure6, it can be seen that the solubility of vanillyl alcohol in all the selected pure solvents increases with increasing temperature. At a given temperature, except methyl cyanide, the solubility in these selected pure solvents can be ranked as ethanol ＞ 2-propanol ＞ 1-butanol ＞ 1-pentanol ＞ 3-methyl-1-butanol ＞ ethyl acetate ＞ butyl
acetate. Generally, the solubility of the solute in different solvents follows the “like dissolves like” principle which indicates that the order of solubility in the solvents selected should be consistent with the polarity. It is well known that the dielectric constant is a key index of polarity. However, according to the dielectric constant(D) [23], the sequence of polarity should be: methyl cyanide(D=35.7)＞ ethanol(D=25.7) ＞ 2-propanol(D=18.3) ＞ 1-butanol(D=17.3) ＞ 3-methyl-1-butanol(D=14.7) ＞
1-pentanol(D=13.9)＞ethyl acetate(D=6.02)＞butyl acetate(D=5.01). It can be seen that the solubility of vanillyl alcohol does not strictly follow the order of polarity of solvents. It can be explained be the fact that dissolution is a complicated process and
polarity is not the unique factor to affect it. A similar phenomenon has been reported in other compounds, such as DMU [10], and FM [12]. From the structural formula of vanillyl alcohol, it can be seen that the solute molecule has not only a hydrogen bonding acceptor but also a hydrogen bonding donor, which suggests that a hydrogen bond can be formed between the solute and solvent molecules. Thus, in this system, it can be expected that both the van der Waals interaction and hydrogen bond will play an important role in the dissolution process of vanilly alcohol. Gu et al. [27] used statistical analysis method to obtained the values of hydrogen bond donor property (α) and hydrogen bond acceptor property(β). For the selected solvents in this work, the rank of the summation of hydrogen bond donor properties are ethanol= 1-butanol= 1-pentanol＞2-propanol＞methyl cyanide＞ethyl acetate=butyl acetate and the rank of the summation of hydrogen bond acceptor properties are 2-propanol＞ethanol= 1-butanol= 1-pentanol＞ethyl acetate=butyl acetate＞methyl cyanide, respectively. The dielectric constant and the summation of hydrogen bond donor properties and hydrogen bond acceptor properties are depicted in figure7. In conclusion, even though the polarity of methyl cyanide is the highest, its capability for forming a hydrogen bond with vanillyl alcohol is weak, which could result in lower solubility of vanillyl alcohol. In addition, although the polarity of 3-methyl-1-butanol is a little higher than 1-butanol, the steric hindrance of 3-methyl-1 butanol is greater than 1-butanol. As a result, the solubility of vanillyl alcohol in 1-butanol is a greater than is the solubility in 3-methyl-1 butanol. To extend the application range of these solubility results, three thermodynamic models, including the modified Apelblat equation, the λh equation and the Wilson model, were applied to correlate the experimental solubility results. The calculated solubility of vanillyl alcohol in all the selected solvents by the three models is listed in table 3. Parameters of these models were obtained by fitting the experimental values in Matlab and the results are shown in table 4-6. The root-mean-square deviations (RMSD) and average relative deviation (ARD%) are applied to assess the correlation results [28]:
1
1 RMSD = N
cal 2 x1,exp i − x1, i ( ) ∑ exp x1,i i =1 N
(10)
cal exp 100 N x1,i − x1,i ARD% = ∑ xexp N i =1 1,i
cal
where xi
exp
and xi
(11)
stand for the calculated solubility and the experimental
solubility values, respectively. The N represents the number of the experimental points. The calculated results of RMSD, ARD are also listed in table 3. It can be clearly seen from table 3 that the Apelblat models gives better fitting results with all the ARD% values lower than 5%, which suggests that the experimental and the correlated results determined by Apelblat model equation are in good agreement at all tested temperatures. 4.3. Dissolution thermodynamic properties In this study, for the vanillyl alcohol-solvent system, the dissolution process can be assumed to consist of four energetic steps (heating, fusion, cooling and mixing processes) in theory. Then the Gibbs energy of dissolution (∆disG), the enthalpy of dissolution (∆disH) and the entropy of dissolution (∆disS) can be calculated by the following equation: ∆disM = x(∆heatM + ∆fusM + ∆coolM) + ∆mixM
(12)
where M can be replaced by G, H, and S; x represents the mole fraction solubility of vanillyl alcohol; ∆heatM and ∆coolM stand for the thermodynamic properties of heating and cooling process, respectively. The ∆fusM is the fusion thermodynamic properties; ∆mixM represents the mixing properties. For the heating and cooling process, it is reasonable to assume that the difference of heat capacity of solid state vanillyl alcohol and the heat capacity of liquid state vanillyl alcohol(∆CP)is approximated by the entropy of fusion, calculated as ∆CP≈∆fusS = ∆fusH/Tm [29,30], and the thermodynamic properties can be determined
by the following equations: ∆(heat + cool)H = ∆Cp(Tm – T)
ln(Tm/T)
(13) (14)
heat)G
= ∆(cool + heat)H - /T ∆(cool + heat)S
(15)
(15)
Besides, during the phase transition of solute, the system is in equilibrium, so ∆fusG=0.
The mixing properties of vanillyl alcohol including ∆mixG, ∆mixS, and ∆mixH, could be determined by: ∆mixG =
GE + ∆mixGid
(16)
∆mixH =
HE + ∆mixHid
(17)
∆mixG =
SE + ∆mixSid
(18)
where GE,HE and SE represent the excess Gibbs energy, excess enthalpy and excess entropy, respectively, and ∆mixGid, ∆mixHid, ∆mixSid stand for mixing Gibbs energy, mixing enthalpy and mixing entropy of the ideal solution, respectively. For an ideal solution system, the mixing properties can be defined by the following equation: ∆mixGid = RT(x1lnx1 + x2lnx2)
(19)
∆mixSid = R(x1lnx1 + x2lnx2)
(20)
∆mixHid = 0
(21)
where x1 and x2 stand for the mole fraction of solute and solvent in solution, respectively. According to the Wilson model, the excess mixing properties can be deduced by the following equations [16]:
GE = RT (x1 ln γ 1 + x2 ln γ 2 )
(22)
where γ1 and γ2 refer to the activity coefficient of solute and solvent in the real solution. Their values are listed in table 7. In this work, based on equations (6-8), GE, HE and SE in the binary system can be defined by the following equations:
GE = − RT [ x1 ln( x1 + x2 Λ12 ) + x2 ln( x2 + x1Λ 21 )]
(23)
∆λ Λ ∆λ21Λ 21 ∂(GE / T ) ) = x1 x2 ( 12 12 + H E = −T 2 x1 + Λ12 x2 x2 + Λ21 x1 ∂T SE =
H E − GE T
(24) (25)
In order to know the contributions of enthalpy and entropy to the dissolution process, %ζH (the relative contribution of enthalpy) and %ζTS(the relative contribution od entropy) were calculated by the following equations [31,32]:
%ζ H = 100 ×
∆H d ∆H d + T ∆Sd
(26)
%ζ TS = 100 ×
T ∆Sd ∆H d + T ∆S d
(27)
According to the experimental solubility values and the fitted Wilson model parameters, the values of ∆disG, ∆disS, and ∆disH can be calculated. The results are shown in table 7.The relative contributions of enthalpy and entropy to the dissolution process in the eight pure solvents are also listed in table 7. It can be seen from table7 that the values of ∆disG are negative, which indicates the dissolution process in all the selected solvents is spontaneous. It is known that lower values of ∆disG leads to greater solubility. The values of ∆disG obtained in this work decrease with the increase ng of temperature, which is consistent with the trend of solubility within the tested temperature range. Besides, the values of ∆disS and ∆disH are all positive, which suggests that the dissolution process in all selected solvents is entropy-driven and endothermic. In all cases, the values of %ζH are lower than 49.6 and the values of %ζTS are higher than 50.4. It can be concluded that the main contributor to ∆disG is entropy, which is consistent with the results that the dissolution process is entropy-driven. 5. Conclusions
In this study, the gravimetric method was applied to measure the solubility of vanillyl alcohol in eight pure solvents, including ethanol, 2-propanol, 1-butanol, 1-pentanol, 3-methyl-1butanol, methyl cyanide, ethyl acetate, and butyl acetate in the temperature ranges from 293.15K to 343.15K at atmospheric pressure. It was found
that the solubility of vanillyl alcohol in ethanol is the highest while the solubility in butyl acetate is the least among all the selected solvents. The solubility values increase with the temperature rise. The experimental solubility values for vanillyl alcohol in the above mentioned pure solvents were well correlated and analysed by using the modified Apelblat equation, the λh equation and the Wilson equation. The correlated results show that the modified Apelblat equation provides better correlation results. Furthermore, based on the Wilson equation, the dissolution thermodynamic properties, including enthalpy, entropy and Gibbs energy were calculated. At all temperatures studied, the enthalpy and entropy increase with the increasing temperature. On the contrary, the Gibbs energy decreases with rising temperature. The results indicate that the dissolution process in all the tested solvents is spontaneous and entropy-driven.
Author information Corresponding Author
*Tel: 86-22-27405754. Fax: 86-22-27314971 E-mail: [email protected] Notes
The authors declare no competing financial interest.
Acknowledgements
This research is financially supported by The Natural Science Foundation of Hebei Province (B2015202090) and Major National Scientific Instrument Development Project (No.21527812)..
References
[1] I.S. Kim, D.K. Choi, H.J. Jung, Molecules 16 (2011) 5349-5361.
[2] R.H.H.V.D. Heuvel, M.W. Fraaije, C. Laane, W.J.H.V. Berkel, J. Agric. Food. Chem.49 (2001) 2954-2958. [3] H.J. Jung, Y.S. Song, C.J. Lim, E.H. Park, Arch. Pharmacal Res. 31 (2008) 1275-1279. [4] C.L. Hsieh, C.H. Chang, S.Y. Chiang, T.C. Li, N.Y. Tang, C.Z. Pon, C.T. Hsieh, J.G. Lin, Life Sci 67 (2000) 1185-1195. [5] Hsu L C, Wen Z H, Lee K Y. US20090258951[P]. 2009. [6] Q. Wang, S.P. Li, Acta Crystallogr. Sect. E: Struct. Rep. Online 65 (2009) o2838. [7] J. Li, W. Zhao, B. Ying, J. Wang, Ind. Eng. Chem. Res. 52 (2013) 3019-3026. [8] X. Huang, J. Wang, H. Hao, J. Ouyang, Y. Gao, Y. Bao, Y. Wang, Q. Yin, Fluid Phase Equilib. 394 (2015) 148-155. [9] C. Wang, Y. Wang, Q. Yin, Z. Xu, Y. Bao, B. Hou, W. Liu, H. Hao, J. Chem. Eng. Data 60 (2015) 3053-3061. [10]P. Zhu, Y. Chen, M. Zhang, Y. Bao, C. Xie, B. Hou, J. Gong, W. Chen, J. Chem. Thermodyn. (2016) 9–16. [11]G. Wang, Y. Wang, Y. Ma, H. Hao, Q. Luan, H. Wang, J. Chem. Thermodyn. 77 (2014) 144–150. [12]Y. Qin, H. Wang, P. Yang, S. Du, C. Huang, Y. Du, S. Wu, J. Gong, Q. Yin, Fluid Phase Equilib.403 (2015) 145-152. [13]J. Yang, H. Wu, Y. Wang, Q. Luan, J. Zhang, G. Wang, H. Hao, J. Chem. Thermodyn. 83 (2015) 77–84. [14]J. Ouyang, J. Wang, X. Huang, Y. Bao, Y. Wang, Q. Yin, A. Liu, X. Li, H. Hao, J. Chem. Thermodyn. 91 (2015) 73-79. [15]E.M. Gonçalves, M.E.M.D. Piedade, J. Chem. Thermodyn. 47 (2012) 362-371. [16]A. Apelblat, E. Manzurola, J. Chem. Thermodyn. 31 (1999) 85-91. [17]R.V. Orye, J.M. Prausnitz, Ind. Eng. Chem. Res. 57 (1965) 18-26. [18]J. Chen, Z.X. Zeng, W.L. Xue, D. Wang, Y. Huang, Ind. Eng. Chem. Res. 50 (2011) 11755-11762. [19]H. Buchowski, A. Ksiazczak, S. Pietrzyk, J. Phys. Chem. 84 (1980) 975-979. [20]H. Yan, Z. Wang, J. Wang, Ind. Eng. Chem. Res. 51 (2012) 2808-2813. [21]H. Renon, J.M. Prausnitz, AlChE J. 14 (1968) 135–144. [22]G.M. Wilson, J. Am. Chem. Soc. 86 (1964). [23] Smallwood,I.M, Wiley: New York,1996. [24] Goethals, G, Natuurwetenschappelijk Tijdschrift (Ghent) 18,(1936), 249-55. [25] Pearl, Irwin A, J. Org. Chem. 12,(1947),79-84. [26] Barnes, R. A, An. Acad. Bras. Cienc. 52,(1980),515-20. [27]C.H. Gu, H. Li, R.B. Gandhi, K. Raghavan, Int. J. Pharm 283 (2004) 117-125.
[28]J. Wang, C. Xie, Q. Yin, L. Tao, J. Lv, Y. Wang, F. He, H. Hao, J. Chem. Thermodyn. 95 (2016) 63-71. [29] Neau, S. H., G. L. Flynn, Pharm. Res. 7(1990):1157-62. [30] J.Yan, Q. Yin, C.Jiang, J. Gong, M. Zhang, Y. Wang, B. Hou, H. Hao, Fluid Phase Equilib. 406(2015):77-90. [31]D.R. Delgado, F. Martínez, Fluid Phase Equilib. 360 (2013) 88-96. [32]W. Tang, C. Xie, Z. Wang, S. Wu, Y. Feng, X. Wang, J. Wang, J. Gong, Fluid Phase Equilib. 363 (2014) 86-96.
Table headings: Table 1
The sources and mass fraction purity of the materials used in this paper. a,b Table 2
Molar volumes of vanillyl alcohol and all the organic solvents used. Table 3
Experimental and correlated mole fraction solubility of vaillyl alcohol in selected solvents over the temperature range from 293.15 K to 343.15 K (p = 101.3 kPa ).a ,b ,c Table 4
The parameters of the modified Apelblat equation for vanillyl alcohol in different pure solvents. a Table 5
The parameters of the λh equation for vanillyl alcohol in different pure solvents. a Table 6
The parameters of the Wilson equation for vanillyl alcohol in different pure solvents. a
Table 7
The dissolution thermodynamic properties of vanillyl alcohol in eight pure solvents. a
Figure captions: Figure1. Chemical structure (a) and three-dimensional structure (b) of vanillyl alcohol Figure2. The thermo-gravimetric (TG) curves for each drying phase at the experimental temperature of 303.15K for different solvents. The TG patterns from bottom to top in this diagram are raw material and the patterns of drying phase in ethanol; 2-propanol; 1-butanol; 1-pentanol; 3-methyl-butanol; methyl cyanide; ethyl acetate; butyl acetate, respectively.
Figure3. X-ray powder diffraction pattern of vanillyl alcohol Figure4. The schematic diagram of the XRPD patterns for the solid phases after solubility experiments for different solvents. The XRPD patterns from bottom to top in this schematic diagram are raw material and the patterns of solid phase in ethanol; 2-propanol; 1-butanol; 1-pentanol; 3-methyl-butanol; methyl cyanide; ethyl acetate; butyl acetate, respectively. Figure5. DSC plot of vanillyl alcohol Figure6. Experimental solubility values for vanillyl alcohol in pure organic solvents:(■)ethanol;(◄)2-propanol;(●)1-butanol;(▲)1-pentanol;(▼)3-methyl-bu tanol;(▶ ▶)methyl cyanide;(★ ★)ethyl acetate;(◆ ◆)butyl acetate.The solid lines are correlated values based on the Modified Apelblat model. Figure7. The dielectric constant, summation of hydrogen bond donor properties and hydrogen bond acceptor properties of each solvent
Table 1
The sources and mass fraction purity of the materials used in this paper. a, b Substance Vanillyl alcohol Ethanol 2-Propanol 1-Butanol 1-pentanol 3-methyl-1-buta nol Methyl cyanide Ethyl acetate 1-Buthyl acetate
Source Jiangxi zhengtong Chemical Co., Ltd, China Tianjin Jiangtian Chemical Co., Ltd, China Tianjin Jiangtian Chemical Co., Ltd, China Tianjin Jiangtian Chemical Co., Ltd, China Tianjin Jiangtian Chemical Co., Ltd, China Tianjin Jiangtian Chemical Co., Ltd, China Tianjin Jiangtian Chemical Co., Ltd, China Tianjin Jiangtian Chemical Co., Ltd, China Tianjin Jiangtian Chemical Co., Ltd, China
Mass fraction purity
Purification method
Analysis method
≥0.995
None
HPLCa
﹥0.997
None
GCb
﹥0.997
None
GCb
﹥0.997
None
GCb
﹥0.997
None
GCb
﹥0.997
None
GCb
﹥0.997
None
GCb
﹥0.997
None
GCb
﹥0.997
None
GCb
a
High-performance liquid chromatography, which was carried out by Jiangxi
zhengtong Chemical Co., Ltd, China b
Gas chromatography, which was carried out by Tianjin Jiangtian Chemical Co.,
Ltd, China
Table 2
Molar volumes of vanillyl alcohol and all the organic solvents used. substance
Vanillyl alcohola
Ethanolb
2-Propanolb
V/(cm3·mol-1)
282.7
58.37
76.43 b
1-Butanolb
1-pentanolb
91.53
108.2
substance
3-methyl-1butanolb
Methyl cyanideb
Ethyl acetate
1-Buthyl acetateb
V(cm3·mol-1)
108.9
52.48
97.83
131.9
a
The molar volume of vanillyl alcohol was calculated by Eqs (9).
b
The molar volume of each solvent (T=293.15K)was obtained from reference[23].
Table 3
Experimental and correlated mole fraction solubility of vaillyl alcohol in selected solvents over the temperature range from 293.15 K to 343.15 K (p = 101.3 kPa ).a ,b ,c
T/K 293.15 303.15 313.15 323.15 333.15 343.15 ARDb
102x1exp,a 4.42 6.27 9.36 14.2 20.5 31.7
102RMSDb 293.15 303.15 313.15 323.15 333.15 343.15 ARDb
2.84 4.18 5.78 9.57 14.9 23.7
102RMSDb 293.15 303.15 313.15 323.15 333.15 343.15 ARDb
2.34 3.93 5.38 9.02 13.4 18.2
102RMSDb 293.15 303.15 313.15 323.15 333.15 343.15 ARDb
2.14 3.38 4.90 7.28 10.2 15.5
102RMSDb 293.15 303.15 313.15 323.15
2.25 3.02 4.47 6.52
102x1Apel
102x1λh
102x1Wilson
4.14 6.48 9.83 14.5 20.8 29.1 4.45
3.57 5.90 9.50 14.7 21.6 30.1 6.84
0.183 2-Propanol 2.76 4.06 6.13 9.45 14.9 23.7 2.29
1.10
0.901
2.60 4.17 6.50 9.88 14.7 21.4 6.03
2.37 3.84 6.07 9.69 15.2 23.5 5.59
0.167 1-Butanol 2.18 3.69 5.91 9.01 13.1 18.4 4.34
1.00
0.301
2.36 3.74 5.77 8.71 12.9 18.8 3.93
2.57 3.93 5.86 8.73 12.8 18.6 4.78
1.30 1-Pentanol 2.28 3.31 4.84 7.10 10.5 15.4 2.57
0.385
0.378
2.17 3.3 4.93 7.23 10.1 15.2 1.64
2.14 3.26 4.87 7.19 10.5 15.4 1.46
0.149
0.139
2.13 3.15 4.57 6.55
1.97 2.98 4.44 6.52
Ethanol 4.44 6.38 9.33 13.9 20.8 31.6 1.02
0.152 3-Methyl-1-Butanol 2.27 3.11 4.39 6.34
333.15 343.15 ARDb
9.12 14.0
102RMSDb 293.15 303.15 313.15 323.15 333.15 343.15 ARDb
1.72 2.62 4.15 7.13 12.7 22.0
102RMSDb 293.15 303.15 313.15 323.15 333.15 343.15 ARDb
1.76 2.96 3.93 6.82 10.0 16.3
102RMSDb 293.15 303.15 313.15 323.15 333.15 343.15 ARDb
0.980 1.77 2.70 4.28 6.53 10.7
102RMSDb
a
9.34 14.0 1.87
9.34 13.3 3.25
9.45 13.9 3.27
0.129 Methyl cyanide 1.60 2.58 4.28 7.26 12.5 22.0 2.51
0.320
0.193
1.51 2.69 4.62 7.67 12.3 19.2 8.37
1.46 2.47 4.19 7.26 12.8 21.9 4.14
0.120 Ethyl Acetate 1.86 2.76 4.20 6.51 10.2 16.3 4.27
1.19
0.144
1.72 2.78 4.38 6.75 10.2 15.3 4.87
1.69 2.71 4.20 6.63 10.2 16.2 4.06
0.208 Butyl Acetate 1.10 1.70 2.66 4.19 6.67 10.7 3.76
0.482
0.192
1.00 1.67 2.72 4.32 6.74 10.4 2.57
1.05 1.70 2.68 4.23 6.62 10.7 2.46
0.906
0.148
0.0604
xexp is the experimentally solubility; xApel, xλh and xWilson represent the calculated
mole fraction solubility correlated by the modified Apelblat equation, λh equation,and Wislon model, respectively. b
ARD and RMSD are the average relative deviation and root-mean-square deviations,
respectively, they are calculated based on Eqs.(10)-(11). c
Standard uncertainty of temperature is u(T)=0.005 K. The standard uncertainty of
pressure is u(p)=0.3kPa. The relative standard uncertainty of solubility is ur(x1)=0.05.
Table 4
The parameters of the modified Apelblat equation for vanillyl alcohol in different pure solvents. a solvent Ethanol 2-Propanol 1-Butanol 1-Pentanol 3-Methyl-1-Butanol Methyl cyanide Ethyl Acetate Butyl Acetate a b
Modified Apelblat equation Aa/102 Ba/103 -2.519±0.6461 8.339±3.098 -3.127±0.8910 10.85±4.285 1.546±1.777 -11.03±8.543 -1.825±1.061 5.149±5.086 -2.941±0.9673 10.53±4.630 -3.543±0.9128 11.98±4.4097 -2.893±1.627 9.703±7.823 -2.419±1.138 7.282±5.478
Ca/10 3.880±0.9521 4.490±1.313 -2.127±2.617 2.837±1.563 4.479±1.425 5.444±1.343 4.440±2.397 3.741±1.676
A, B and C are the parameters of the modified Apelblat equation. The number in the right side of “±” means the standard error of each coefficient in
different solvent. (0.95 level of confidence) . Table 5
The parameters of the λh equation for vanillyl alcohol in different pure solvents. a
λh equation
solvent
λa/102
ha/102
Ethanol 2-Propanol 1-Butanol 1-Pentanol 3-Methyl-1-Butanol Methyl cyanide Ethyl Acetate Butyl Acetate
122.2±19.78 87.36±19.88 69.29±8.634 41.22±2.462 31.87±3.694 116.0±30.07 58.42±9.891 42.45±3.261
32.89±3.454 47.93±7.154 58.19±4.693 85.77±2.823 102.6±6.920 44.52±8.202 72.05±8.009 105.4±5.446
a
λ and h are the parameters of the λh equation.
b
The number in the right side of “±” means the standard error of each coefficient in
different solvent. (0.95 level of confidence)
Table 6
The parameters of the Wilson equation for vanillyl alcohol in different pure solvents. a
Wilson equation solvent
∆λ12/kJ·mol-1a
∆λ21/kJ· mol-1a
Ethanol 2-Propanol 1-Butanol 1-Pentanol 3-Methyl-1-Butanol Methyl cyanide Ethyl Acetate Butyl Acetate
0.1459±1.681 -0.6483±0.5030 -2.709±0.6080 -1.998±0.2258 -2.204±0.3177 -0.1240±0.2128 -0.7321±0.3693 0.6640±0.1638
1.851±0.4024 2.493±0.2402 4.721±0.9181 4.989±0.5115 6.170±0.9334 3.293±0.06717 0.3310±0.3168 3.342±0.1868
a
∆λ12 and ∆λ21 are the parameters of the Wilson equation.
b
The number in the right side of “±” means the standard error of each coefficient in
different solvent. (0.95 level of confidence)
Table 7
The dissolution thermodynamic properties of vanillyl alcohol in eight pure solvents. a
T/K
∆disG a /(kJ·mol-1)
∆disH a /(kJ·mol-1)
∆disS a /(J·K-1·mol-1)
%ζHb
%ζTSb
γ1c
γ2c
6.48 8.82 12.6 18.0 24.7 35.6
49.6 49.2 49.0 48.8 48.6 48.7
50.4 50.8 51.0 51.2 51.4 51.3
1.25 1.15 1.05 0.98 0.939 0.932
1.00 1.01 1.01 1.01 1.01 1.01
4.04 5.73 7.62
49.5 49.2 48.8
50.5 50.8 51.2
1.89 1.76 1.65
1.00 1.00 1.00
Ethanol
293.2 303.2 313.2 323.2 333.2 343.2
-0.365 -0.506 -0.718 -1.01 -1.34 -1.76
1.87 2.59 3.78 5.55 7.80 11.6
293.2 303.2 313.2
-0.239 -0.339 -0.454
1.16 1.68 2.28
2-Propanol
323.2 333.2 343.2
-0.677 -0.949 -1.30
3.69 5.63 8.67
12.0 17.8 26.5
48.8 48.7 48.8
51.2 51.3 51.2
1.49 1.34 1.2
1.01 1.02 1.04
3.14 5.02 6.62 10.5 15.0 19.6
49.0 48.9 48.6 48.7 48.7 48.5
51.0 51.1 51.4 51.3 51.3 51.5
1.74 1.72 1.71 1.65 1.58 1.51
1.00 1.00 1.00 1.00 1.01 1.02
0.810 2.87 1.26 4.32 1.80 6.01 2.62 8.55 3.38 10.8 5.46 16.9 3-Methyl-1-butanol 0.840 2.95 1.11 3.82 1.62 5.42 2.31 7.57 3.18 10.2 4.81 14.9 Methyl cyanide 0.730 2.55 1.10 3.74 1.71 5.69 2.89 9.31 5.02 15.7 8.36 25.4 Ethyl acetate 0.710 2.48 1.16 3.97 1.52 5.10 2.59 8.40 3.73 11.8 5.94 18.2 Butyl acetate 0.400 1.41 0.710 2.42 1.06 3.54
49.2 49.1 48.8 48.7 48.4 48.6
50.8 50.9 51.2 51.3 51.6 51.4
2.09 2.08 2.05 2.01 1.94 1.83
1.00 1.00 1.00 1.00 1.01 1.02
49.3 48.9 48.8 48.6 48.4 48.5
50.7 51.1 51.2 51.4 51.6 51.5
2.27 2.27 2.25 2.21 2.15 2.03
1.00 1.00 1.00 1.00 1.01 1.01
49.5 49.2 49.0 49.0 49.0 49.0
50.5 50.8 51.0 51.0 51.0 51.0
3.07 2.74 2.39 1.99 1.59 1.29
1.00 1.00 1.01 1.01 1.03 1.07
49.2 49.2 48.8 48.8 48.7 48.7
50.8 50.8 51.2 51.2 51.3 51.3
2.64 2.5 2.38 2.18 1.99 1.73
1.00 1.00 1.00 1.01 1.01 1.03
49.1 49.1 48.9
50.9 50.9 51.1
4.26 3.99 3.73
1.00 1.00 1.00
1-Butanol
293.2 303.2 313.2 323.2 333.2 343.2
-0.215 -0.330 -0.434 -0.641 -0.855 -1.06
0.880 1.46 1.96 3.24 4.74 6.33 1-Pentanol
293.2 303.2 313.2 323.2 333.2 343.2
-0.189 -0.278 -0.379 -0.518 -0.644 -0.894
293.2 303.2 313.2 323.2 333.2 343.2
-0.194 -0.253 -0.350 -0.471 -0.608 -0.810
293.2 303.2 313.2 323.2 333.2 343.2
-0.145 -0.212 -0.317 -0.494 -0.774 -1.15
293.2 303.2 313.2 323.2 333.2 343.2
-0.155 -0.241 -0.313 -0.480 -0.648 -0.907
293.2 303.2 313.2
-0.0890 -0.146 -0.210
323.2 333.2 343.2
-0.305 -0.423 -0.601
1.65 2.47 3.95
5.36 7.81 12.1
a
∆disG, ∆disS and ∆disG are calculated based on Eqs (12)-(25).
b
%ζH and %ζTS are calculated by Eqs (26)-(27).
c
48.8 48.7 48.7
51.2 51.3 51.3
γ1 andγ2 are calculated by Eqs (6)-(8).
d
The combined expanded uncertainties U are Uc(∆disG)=0.060∆disG; Uc(∆disH)=0.055 ∆disH; Uc(∆disS)=0.060∆disS . (0.95 level of confidence).
Figure1.Chemical structure (a) and three-dimensional structure (b) of vanillyl alcohol
3.41 3.07 2.63
1.00 1.01 1.02
Figure2 The thermo-gravimetric (TG) curves for each drying phase at the experiment temperature of 303.15K for different solvents. The TG patterns from bottom to top in this diagram are raw material and the patterns of drying phase in ethanol; 2-propanol; 1-butanol; 1-pentanol; 3-methyl-butanol; methyl cyanide; ethyl acetate; butyl acetate, respectively.
Figure3. X-ray powder diffraction pattern of vanillyl alcohol
Figure4. The schematic diagram of the XRPD patterns for all the solid phase after solubility experiments for different solvents. The XRPD patterns from bottom to top in this schematic diagram are raw material and the patterns of solid phase in ethanol; 2-propanol; 1-butanol; 1-pentanol; 3-methyl-butanol; methyl cyanide; ethyl acetate; butyl acetate, respectively.
Figure 5. DSC plot of vanillyl alcohol
Figure6. Experimental solubility values for vanillyl alcohol in pure organic solvents:(■)ethanol;(◄)2-propanol;(●)1-butanol;(▲)1-pentanol;(▼)3-methyl-bu tanol;(▶ ▶)methyl cyanide;(★ ★)ethyl acetate;(◆ ◆) butyl acetate. The solid lines are correlated values based on the Modified Apelblat model.
Figure7. The dielectric constant, summation of hydrogen bond donor properties and hydrogen bond acceptor properties of each solvent
The solubilities of vanillyl alcohol in eight pure solvents were determined by
using a static gravimetric method. The capability of vanillyl alcohol to form hydrogen bond with solvents was
applied to explain the difference of solubility in different solvents. Dissolution thermodynamic properties of vanillyl alcohol were calculated and
discussed.