Solubility measurement, model evaluation and Hansen solubility parameter of piperonylonitrile in four binary solvents
Introduction
Chemically, piperonylonitrile is 1,3-benzodioxole-5-carbonitrile (CAS, 4421–09-4; Fig. 1; molar mass: 147.13 g·mol−1), which has the molecular formula of C8H5NO2 [1]. Piperonylonitrile, which commonly appears as a white acicular crystal, is an important intermediate widely used in the manufacture of medicine, pesticide, synthetic fibre and functional high molecule materials [2], [3]. In recent years, piperonylonitrile and its compounds have been used in the application of tobacco sweetener, high-grade liquid crystal material, anti-cancer medicine and so forth [2], [4]. As a newly-developed tobacco sweetener, the effect on cigarette flavour of piperonylonitrile is higher than that of traditional sweetener. As a kind of perfume product, piperonylonitrile possesses higher chemical stability, oxidation-resistivity as well as acid and alkali resistance. It is also relatively insensitive to skin, hence, piperonylonitrile is frequently used to replace or combine with piperonal in the formulations of daily chemical and essence [5]. The industrial synthesis methods of piperonylonitrile have been reported in recent years [6], [7]. It is widely known that the purity and crystal form of a drug are of vital importance for the further applications in pharmaceutical and fine chemical industry [8], [9]. In addition, the solution crystallization process is a very important unit operation for obtaining desired final product [10]. And the solubilities of a drug in organic solvents are the fundamental study on the choice of purification and crystallization method. Therefore, the fundamental data, including the solubility and thermodynamic parameters are worthy of research for its purification and crystallization process.
From the published solubility data of piperonylonitrile in thirteen mono-solvents, [11] it was clearly observed that the solubilities of piperonylonitrile in isopropanol, ethanol and n-propanol were relatively low while the solubilities in acetone, 1,4-dioxane, methyl acetate and DMF were relatively high. The selection of anti-solvent is an important part in the solubility measurement of piperonylonitrile in binary mixed solvents. Although the minimal solubility of piperonylonitrile was found in isopropanol, there were some disadvantages that limited the wide use of isopropanol in pharmaceutical fields, such as strong odor [12] and toxic. It is well-known that n-propanol is not frequently used as co-solvent in biological-pharmacy industry [13]. Compared with isopropanol and n-propanol, ethanol is an environmentally safe and commonly used alcoholic solvent in pharmaceutical liquid formulations [14]. Besides, no crystalline transformation or degradation of piperonylonitrile from above-mentioned five mono-solvents was observed during the experiments. Hence, ethanol was chosen as anti-solvent and DMF, 1,4-dioxane, methyl acetate as well as acetone were recorded as positive solvent in this research. Regarding the selection of temperature range for solubility studies, the melting point (Tm) of solute and boiling temperature (Tb) of solvents must be considered. In this research, the maximum experimental temperature cannot exceed the Tm value of piperonylonitrile (Tm = 366.75 K) and Tb values of selected solvents, such as ethanol (Tb = 351.65 K), DMF (Tb = 426.15 K), methyl acetate (Tb = 329.95 K), acetone (Tb = 329.15 K) and 1,4-dioxane (Tb = 374.25 K) [1]. Therefore, the experimental temperature range was set as “T = 278.15 K − 323.15 K”. To data, there is no accessible research on the solid–liquid equilibrium data and mixing thermodynamic properties of piperonylonitrile in different binary solvent mixtures.
In this above framework, the current research intends to measure the solubilities of piperonylonitrile in four various binary solvent mixtures (DMF + ethanol, 1,4-dioxane + ethanol, methyl acetate + ethanol, acetone + ethanol) via laser monitoring method between T = (278.15 K to 323.15 K). Four thermodynamic models, namely UNIQUAC, NRTL, Margules and Wilson model, were implemented to regress the solubility data of piperonylonitrile. Moreover, Hansen solubility parameter was applied to describe and reveal the affinity between piperonylonitrile and involved binary mixtures. Finally, the mixing thermodynamic properties were calculated and discussed by utilizing the Wilson model and experimental solubility data.
Section snippets
Materials
Piperonylonitrile, DMF and ethanol were procured from Shanghai Macklin Biochemical Technology Co., Ltd. (Shanghai, China). Acetone and 1,4-dioxane were acquired from Tianjin kermel chemical reagent Co., Ltd. (Tianjin, China). Methyl acetate was obtained from Sinopharm chemical reagent. Co., Ltd. (Shanghai, China). More detailed information of these materials involved in this research are listed in Table S1 (Supporting Information).[11], [15]
Differential scanning calorimeter (DSC) measurement of piperonylonitrile
The characterization of raw and equilibrated
Hansen solubility parameter
Hansen solubility parameter (HSP) was estimated by Charles M. Hansen in 1967.[16] This concept is based on the principle that the more similar are the HSP values between two materials, the higher is their miscibility. To explain the affinity between piperonylonitrile and neat solvents or mixed solvents, various HSP for piperonylonitrile and investigated solvents, including δt (total HSP), δh (hydrogen-bonded HSP), δp (polar HSP) and δd (dispersion HSP) were presented in this work. These partial
DSC analysis
The DSC thermograms of raw and equilibrated piperonylonitrile from four different binary solvents were presented in Fig. 2. It can be seen from Fig. 2 that only one endothermic peak of four recovered equilibrated piperonylonitrile is observed, which is consistent with that of raw material. The values of Tm and ΔfusH of all samples have also been presented in Fig. 2. With the analysis of all DSC profiles combined, the thermal behaviour of equilibrated piperonylonitrile is accordant with that of
Conclusion
The solubility of piperonylonitrile in ethanol + (1,4-dioxane, methyl acetate, acetone or DMF) binary solvent mixtures was experimentally determined by applying laser monitoring method from 278.15 K to 323.15 K under pressure of “p = 0.1 MPa”. It was found that the solubility of piperonylonitrile in all mixed solvents increased with the enhancement of experimental temperature and mass fraction of positive solvents. Various solubility parameters (δd, δp, δh, δt, Δδh and ) of mixed solvents
CRediT authorship contribution statement
Haixia He: Conceptualization, Methodology, Software, Validation, Formal analysis, Investigation, Data curation, Writing - original draft. Renren Sun: Software, Validation, Resources. Yameng Wan: Validation, Resources. Gaoliang Jiang: Data curation, Resources. Jiao Sha: Software, Resources. Yu Li: Writing - review & editing, Supervision. Tao Li: Project administration, Funding acquisition, Writing - review & editing, Supervision. Baozeng Ren: Project administration, Funding acquisition, Writing
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
This report was financially supported by the Science and technology project of Henan province (No. 182102210002) and Key Research Projects of Henan Higher Education Institutions (No. 19A530004).
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