Conductor-like Screening Model Research Articles

Theoretical and experimental study of calcium extraction using ionic liquids: COSMO-RS approach

The current investigation is aimed to find the effective Task-Specific Ionic Liquid (TSIL) for the extraction of the calcium ion through the quick screening method based on the Conductor-like Screening Model for Real Solvents (COSMO-RS). From the several prescreened cations and anions with different functional groups, a set of appropriate combinations were preliminarily selected to be examined for their efficiency of the calcium ion extraction. With the aid of the COSMO-RS model, the values of the octanol–water partition coefficient (Kow), melting point, and viscosity of the selected TSILs, as well as the infinite dilution chemical potential of the CaCl2 and Ca(NO3)2 salts in the studied TSILs were computed. Analysis of the obtained results led to the conclusion that phosphate anions in combination with tetrabutylammonium [N4444]+ and tetrabutylphosphonium [P4444]+ cations would form more effective TSILs for the Ca2+ extraction. Among these, TSILs tetrabutylammonium bis(2-ethylhexyl) phosphate [N4444][DEHP] and tetrabutylphosphonium bis(2-ethylhexyl) phosphate [P4444][DEHP] were synthesized to verify the computational results, and the extraction of calcium ion was measured as a function of various diluent and concentration of TSILs. The synthesized TSILs represented high calcium extraction efficiency, which was in agreement with the computational result. The mechanism of calcium extraction was studied using the slope analysis method. The stripping of calcium ion from the organic phase and recyclability of TSILs were also investigated.

Exploring the Interactions of Ionic Liquids with Bio-Organic Amphiphiles Using Computational Approaches

Bio-organic amphiphiles have been shown to effectively impart unique physicochemical properties to ionic liquids resulting in the formation of versatile hybrid composites. In this work, we utilized computational methods to probe the formation and properties of hybrids prepared by mixing three newly designed bio-organic amphiphiles with 14 ionic liquids containing cholinium or glycine betaine cations and a variety of anions. The three amphiphiles were designed such that they contain unique biological moieties found in nature by conjugating (a) malic acid with the amino acid glutamine, (b) thiomalic acid with the antiviral, antibacterial pyrazole compound [3-(3,5-dimethyl-1H-pyrazol-1-yl)benzyl]amine, and (c) Fmoc-protected valine with diphenyl amine. Conductor-like screening model for real solvents (COSMO-RS) was used to obtain sigma profiles of the hybrid mixtures and to predict viscosities and mixing enthalpies of each composite. These results were used to determine optimal ionic liquid-bio-organic amphiphile mixtures. Molecular dynamics simulations of three optimal hybrids were then performed, and the interactions involved in the formation of the hybrids were analyzed. Our results indicated that cholinium-based ILs interacted most favorably with the amphiphiles through a variety of inter- and intramolecular interactions. This work serves to illustrate important factors that influence the interactions between bio-organic amphiphiles and bio-ILs and aids in the development of novel ionic liquid-based composites for a wide variety of potential biological applications.

Amino Acid Ester based Phenolic Ionic Liquids as a Potential Solvent for the Bioactive Compound Luteolin: Synthesis, Characterization, and Food Preservation Activity

Ionic liquids (ILs) have gained great attention as potent solubilizing agents of poorly soluble bioactive compounds. The use of Luteolin (LUT) – a natural bioactive compound – is limited because of its poor aqueous solubility. To address this issue, this study reports potential ILs for effectively solubilizing LUT at ambient temperature. First, promising ILs were screened from a potential 180 ILs that were proposed by the combination of 20 standard amino acid ethyl esters cations and nine phenolic acids anions using the conductor-like screening model for real solvents (COSMO-RS); the activity coefficients of LUT at infinite dilution in ILs were used as the screening criteria. Four proline ethyl ester phenolate ILs (PEEP-ILs) composed of a biocompatible proline ethyl ester and bioactive phenolic acids (trans-ferulic, vanillic, p-coumaric, and 4-hydroxybenzoic acid) were selected and synthesized. The synthesized PEEP-ILs were characterized through 1H NMR, FT-IR, elemental analysis, TGA, and DSC. The experimental solubility of LUT in PEEP-ILs (60% IL in water) showed excellent solubility. Among the PEEP-ILs, proline ethyl ester ferulate (IL[ProEt][Fer]) exhibited the best LUT solubility, followed by ILs with p-coumarate (IL[ProEt][Cou]), vanillate (IL[ProEt][Van]), and 4-hydroxybenzoate (IL[ProEt][Ben]). 1H NMR assessment and COSMO-RS prediction confirmed that the ILs facilitated the solubilization of LUT through multiple hydrogen bonding, π − π, and cation − π interactions between the LUT and the ILs. The biocompatibility study revealed that PEEP-ILs were relatively harmless and low toxicity compared with conventional imidazolium, pyridinium, pyrrolidinium, piperidinium, and morpholinium-based ILs. The LUT dissolved in the newly-synthesized PEEP-ILs and demonstrated better organoleptic properties on red apple slices. These results indicate that PEEP-ILs can be potential green alternatives to conventional toxic solvents for dissolving poorly water-soluble bioactive natural preservatives.

Efficient naphthenic acid extraction from high acidic oil using novel 1,5-diazabicyclo[4.3.0]non-5-ene based ionic liquids

In this work, the high acidic crude oil deacidification study was performed with novel 1-alkyl-1,5-diazabicyclo[4.3.0]non-5-ene (DBN) based ionic liquids (ILs). Firstly, we took advantage of the systematic COSMO-RS (Conductor-like Screening Model for Real Solvents) calculations to screen the possible ILs with good acid extraction performance from the combinations of 94 cations and 56 anions. Four 1-alkyl-1,5-diazabicyclo[4.3.0]non-5-enium imidazolide ([DBN-R][IM]) ILs with varying alkyl chains were eventually identified and synthesized successfully. Their deacidification performances were tested experimentally and different factors, including the alkyl chain length, ILs/oil mass ratio, temperature, and the initial total acid number (TAN) value of the simulated acidic oil, were also studied in detail. The experimental results showed that [DBN-R][IM] exhibited excellent performances on naphthenic acids (NAs) removal and [DBN-Et][IM] could achieve 93% of NAs removal employing the ILs/oil mass ratio of 0.06 at room temperature for the acidic oil with the TAN value of 3.28 mg KOH/g. COSMO-RS analyses were also used to elucidate the unusual effects of the alkyl chain length and temperature on the NAs extraction performances. Additionally, a two-step deacidification strategy was proposed aiming at realizing more efficient NAs extraction. Finally, density functional theory (DFT) calculations were carried out and the independent gradient model (IGM) analyses were applied to the IL-NAs system to get insight into the deacidification mechanism of the ILs.

Comparative screening of organic solvents, ionic liquids, and their binary mixtures for vitamin E extraction from deodorizer distillate

Although it is well known that solvent is one of the most important decision variables in liquid-liquid extraction processes, many previous studies focused on a specific class of solvents while neglecting alternatives. This work presents a comparative screening of two types of most extensively studied solvents, i.e., organic solvents (OS) and ionic liquids (ILs), as well as their binary systems for the extraction of vitamin E from methylated oil deodorizer distillates (modelled as a mixture of α-tocopherol and methyllinoleate). For this practically relevant task, the ternary liquid-liquid equilibria (LLE) of {OS or IL + α-tocopherol + methyllinoleate} are first calculated by use of the COnductor-like Screening Model for Real Solvents (COSMO-RS), after which the physical and environmental, health, and safety (EHS) properties of solvents are assessed to identify the top-ranked OS and ILs. To intensify the separation performance, binary solvent systems are also explored, where one of the pre-selected ILs is taken as the first solvent for α-tocopherol and an OS is screened as the second solvent for methyllinoleate. Then, the IL-OS combinations are investigated regarding their binary immiscibility and ranked with respect to the LLE performance in the quaternary system {IL + α-tocopherol + methyllinoleate + OS}. By comparing the extraction distribution coefficient and the selectivity of the top-ranked OS, ILs and IL-OS systems, the notable intensified performance of binary solvent system is proven.

Effect of Water on Phenol Separation from Model Oil with Ionic Liquids Based on COSMO-RS Calculation and Experimental Study.

Ionic liquids (ILs) are widely used in the extraction of phenolic compounds from low-temperature coal tar (LTCT). However, both ILs and LTCT contain a certain amount of water. The existence of water may have a remarkable impact on the phenol separation performance of ILs with different structures. In this work, the capacity and selectivity for m-cresol, as well as the solubility of cumene and dodecane in different IL–H2O mixtures, were firstly calculated by the conductor-like screening model for real solvents (COSMO-RS) at infinite dilution. The calculation covers ILs with different anionic and anionic structures and different water contents. To explore the effect of water in IL on separation performance, 1-ethyl-3-methyl imidazolium acetate ([C2mim][Ac]) was selected as the representative IL, and then the molecular interactions between the [C2mim][Ac]–H2O mixture solvent and solute (including m-cresol, cumene, and dodecane) were analyzed by COSMO-RS. The results indicated that both water and m-cresol could form hydrogen bonds with [C2mim][Ac]. The competition between them leads to decreasing separation performance for m-cresol of the [C2mim][Ac]–H2O mixture with increasing water content. Moreover, through analyses of m-cresol extraction efficiency, distribution coefficient, selectivity, and entrainment of cumene and dodecane, the experimental results confirmed that the presence of water in [C2mim][Ac] had a negative effect on the separation of m-cresol. The viscosity and UV–vis spectra of the [C2mim][Ac]–H2O mixture were also measured. Water in ILs should be removed as much as possible to ensure a better dephenolization effect and avoid phenol containing wastewater.

Prediction of solvation properties of low transition temperature mixtures (LTTMs) using COSMO-RS and NMR approach

The concept of sustainable and green solvent has always highlighted in the field of energy and environmental science. The synthesis and application of natural-based Low Transition Temperature Mixture (LTTM) as a novel and green solvent for the lignocellulose biomass pre-treatment such as delignification of Oil-Palm Empty Fruit Bunch (EFB) have been greatly emphasized. In this present work, the investigation of LTTM efficiency as green solvent in delignification process was conducted using both theoretical and experimental studies. Initially, screening of solvation properties of different types of hydrogen bond acceptor (HBA) and predicted hydrogen bond donor (HBD) for synthesis of LTTMs was conducted using conductor-like screening model (COSMO-RS) software and formation of hydrogen bonding was evidenced using NMR spectroscopy analysis. Three types of HBA namely sucrose, choline chloride and monosodium glutamate were mixed with malic acids as HBD and their charge density distribution on the surface was determined through sigma profile (σ). The COSMO-RS results determined the σ profile of pure component malic acid to be 11.42, sucrose to be 25.37 and the total value of σ profile for mixtures is 14.19 as the best combination of LTTM composition compared to LTTM from choline chloride and monosodium glutamate (MSG). The reliability of the COSMO-RS predictions data was correlated with Nuclear Magnetic Resonance (NMR) analysis through determination of peaks with chemical shifts hydrogen bonding that suggested existence of potential interaction between malic acids and sucrose has occurred.

Encapsulated deep eutectic solvent for esterification of free fatty acid

A novel encapsulated deep eutectic solvent (DES) was introduced for biodiesel production via a two-step process. The DES was encapsulated in medical capsules and were used to reduce the free fatty acid (FFA) content of acidic crude palm oil (ACPO) to the minimum acceptable level (< 1%). The DES was synthesized from methyltriphenylphosphonium bromide (MTPB) and p-toluenesulfonic acid (PTSA). The effects pertaining to different operating conditions such as capsule dosage, reaction time, molar ratio, and reaction temperature were optimized. The FFA content of ACPO was reduced from existing 9.61% to less than 1% under optimum operating conditions. This indicated that encapsulated MTPB-DES performed high catalytic activity in FFA esterification reaction and showed considerable activity even after four consecutive recycling runs. The produced biodiesel after acid esterification and alkaline transesterification met the EN14214 international biodiesel standard specifications. To our best knowledge, this is the first study to introduce an acidic catalyst in capsule form. This method presents a new route for the safe storage of new materials to be used for biofuel production. Conductor-like screening model for real solvents (COSMO-RS) representation of the DES using σ-profile and σ-potential graphs indicated that MTPB and PTSA is a compatible combination due to the balanced presence and affinity towards hydrogen bond donor and hydrogen bond acceptor in each constituent.

Two-Dimensional Infrared Correlation Spectroscopy, Conductor-like Screening Model for Real Solvents, and Density Functional Theory Study on the Adsorption Mechanism of Polyvinylpolypyrrolidone for Effective Phenol Removal in an Aqueous Medium.

The discharge of industrial effluents, such as phenol, into aquatic and soil environments is a global problem due to its serious negative impacts on human health and aquatic ecosystems. In this study, the ability of polyvinylpolypyrrolidone (PVPP) to remove phenol from an aqueous medium was investigated. The results showed that a significant proportion of phenol (up to 74.91%) was removed using PVPP at pH 6.5. Isotherm adsorption experiments of phenol on PVPP indicated that the best-fit adsorption was obtained using Langmuir models. The response peaks of the hydroxyl groups of phenol (OH) and the carboxyl groups (i.e., C=O) of PVPP were altered, indicating the formation of a hydrogen bond between the PVPP and phenol during phenol removal, as characterized using 1D and 2D IR spectroscopy. The resulting complexes were successfully characterized based on their thermodynamic properties, Mulliken charge, and electronic transition using the DFT approach. To clarify the types of interactions taking place in the complex systems, quantum theory of atoms in molecules (QTAIM) analysis, reduced density gradient noncovalent interaction (RDG-NCI) approach, and conductor-like screening model for real solvents (COSMO-RS) approach were also successfully calculated. The results showed that the interactions that occurred in the process of removing phenol by PVPP were through hydrogen bonding (based on RDG-NCI and COSMO-RS), which was identified as an intermediate type (∇2ρ(r) > 0 and H < 0, QTAIM). To gain a deeper understanding of how these interactions occurred, further characterization was performed based on adsorption mechanisms using molecular electrostatic potential, global reactivity, and local reactivity descriptors. The results showed that during hydrogen bond formation, PVPP acts as a nucleophile, whereas phenol acts as an electrophile and the O9 atom (i.e., donor electron) reacts with the H22 atom (i.e., acceptor electron).

Preparation of sustainable activated carbon-alginate beads impregnated with ionic liquid for phenol decontamination

Powder activated carbon (PAC), derived from calligonum pollygonides, was successfully modified with the ionic liquid (IL) trihexyltetradecylphosphonium bromide ([PC6C6C6C14][Br]) in the presence of sodium alginate and characterized using SEM, FTIR and TGA. PAC, granular AC (GAC), AC-alginate and AC-Alg-IL bead were assessed for the removal of phenol from aqueous media via batch adsorption. Both PAC and AC-Alg-IL beads displayed high adsorption capacities, 123 mg/g and 78 mg/g, respectively, under optimized conditions. In contrast, GAC gave a much lower adsorption capacity than AC-ALG-IL beads, indicating that AC-ALG-IL beads are superior as potential adsorbents for this industrial application. Theoretical studies showed that the pseudo-second-order kinetic and Freundlich isotherm models were suitable to describe the adsorption process. The interaction between phenol and AC-Alg-IL beads was analyzed using the conductor-like screening model for realistic solvents (COSMO-RS). It has been concluded that AC-Alg-IL beads can be used as an efficient adsorbent for phenol and other organic compounds.

Application of protic ammonium-based ionic liquids with carboxylate anions for phenol extraction from aqueous solution and their cytotoxicity on human cells

In this work, the removal of phenol from aqueous solution was investigated by screening three ionic liquids (ILs) having one common cation, trioctylammonium (TOA), combined with three different anions, namely 3,4-dimethylbenzoate (IL1), 4-tert-butylbenzoate (IL2), and 4-phenylbutanoate (IL3), at room temperature. The results indicate that [TOA][4-phenylbutanoate] (IL3) gave the best efficiency and, hence, was selected for the optimization of process parameters: pH, contact time, concentration, phase ratio, and temperature. The optimum conditions were found to be pH 5, contact time of 5 min, phase ratio (VIL/Vw) of 1:5, initial concentration of phenol of 3000 ppm, and temperature of 298 K. The extraction thermodynamics were studied, and the enthalpy, entropy, and free energy of partition were evaluated. The modes of interaction of these ILs with phenol were modeled using the Conductor-Like Screening Model for Real Solvent (COSMO-RS). Additionally, the cytotoxicity of these ILs toward human cells was investigated. The results indicate that they possess less toxicity than the more commonly used 1-butyl-1-methylpyrrolidinium bis-(trifluoromethylsulfonyl)imide. It has been concluded from the experimental results that ammonium-based ILs with carboxylate anions are efficient for extraction of phenol from polluted water.

Energy, Structures, and Response Properties with a Fully Coupled QM/AMOEBA/ddCOSMO Implementation.

We present the implementation of a fully coupled polarizable QM/MM/continuum model based on the AMOEBA polarizable force field and the domain decomposition implementation of the conductor-like screening model. Energies, response properties, and analytical gradients with respect to both QM and MM nuclear positions are available, and a generic, atomistic cavity can be employed. The model is linear scaling in memory requirements and computational cost with respect to the number of classical atoms and is therefore suited to model large, complex systems. Using three variants of the green-fluorescent protein, we investigate the overall computational cost of such calculations and the effect of the continuum model on the convergence of the computed properties with respect to the size of the embedding. We also demonstrate the fundamental role of polarization effects by comparing polarizable and nonpolarizable embeddings to fully QM ones.

Vortex assisted dispersive liquid–liquid microextraction based on low transition temperature mixture solvent for the HPLC determination of pyrethroids in water samples: Experimental study and COSMO-RS

A green, simple, and effective vortex-assisted dispersive liquid–liquid microextraction method that utilizes a menthol-based low transition temperature mixture (menthol-LTTM-VADLLME) was developed to extract and preconcentrate four types of pyrethroids, namely bifenthrin, deltamethrin, fenpropathrin, and permethrin from water samples. In addition, quantum chemical-based conductor-like screening model for realistic solvents (COSMO-RS) software was used to predict the molecular interaction between low transition temperature mixtures (LTTMs) and pyrethroids based on their σ-profile, σ-potentials, and activity coefficient at infinite dilution. High performance liquid chromatography (HPLC) was employed for the further separation of the pyrethroids and their quantification. Several key parameters that affect pyrethroid extraction efficiency are identified as the vortex time, type of LTTM, volume of LTTM, type of dispersive solvent, dispersive solvent volume, type of salt, and amount of salt. The extraction time of 90 s and 150 µL of menthol: sesamol at ratio 1:1 were selected as the best conditions, while ionic strength and type of dispersant solvent were not relevant for the extraction of the target compounds. After optimization, the menthol-LTTM-VADLLME method was found to be able to detect pyrethroids in the range of 0.5–1000.0 μg/L with good linearity (correlation coefficient = 0.9988–0.9995). The method detection limit and quantification limit were found to be in the range of 0.05–0.11 μg/L and 0.18–0.35 μg/L, respectively. The relative standard deviation of inter-day and intra-day precisions were 2.2–5.0% (n = 5) and 1.2–1.9% (n = 7) respectively. The optimized method can successively determine pyrethroids in tap, drinking and river water samples with good recoveries of 73–111%. Hence, this method presents a good approach for determining pyrethroid content in water samples.

Simultaneous Extraction of Sulfur and Nitrogen Compounds from Model Diesel Fuel Using Neoteric Green Solvents.

Removal of nitrogen and sulfur compounds from diesel fuel is essential to comply with the increasing stringent regulations. The extraction capability of two deep eutectic solvents, namely, tetrabutylphosphoniumbromide/ethylene glycol, TBPBr/EG, with molar ratio 1:2, and tetrabutylammoniumbromide/ethylene glycol, TBABr/EG, with molar ratio 1:2, in simultaneously extracting basic nitrogen, nonbasic nitrogen, and sulfur compounds represented by pyridine, indoline, and dibenzothiophene (DBT) from n-hexadecane, was investigated. Two pseudo-ternary phase diagrams of (TBPBr/EG + (pyridine + indoline + DBT) + n-hexadecane) and (TBABr/EG + (pyridine + indoline + DBT) + n-hexadecane) were predicted via a conductor-like screening model for real solvents (COSMO-RS) and experimentally validated at 298.15 K and 1 atm. Both solvents showed zero cross-contamination, indicating the suitability of all solvents as extraction solvents. The tie lines obtained for both COSMO-RS and experiments were in agreement and had root-mean-square deviation (RMSD) values of less than 5% for both systems. Selectivity and distribution ratio calculated indicates the suitability of both solvents in extracting sulfur and nitrogen compounds from hexadecane. Two new parameters, namely, extraction efficiency, α, and extraction affinity, β, were introduced to ease the performance comparison of both solvents. TBPBr/EG shows a slightly better performance than TBABr/EG. Other than that, the presence of multiple solutes shows low effects on the performance of these solvents.

Solvent Effects in the Ultraviolet and X-ray Absorption Spectra of Pyridazine in Aqueous Solution.

Electrostatic interaction of the solvent with the solute and fluctuations of the solvent configurations may make excitation energies of the solute different from those in the gas phase. These effects may dominate photoinduced or chemical reaction dynamics in solution systems and can be observed as shifts or broadening of peaks in absorption spectra. In this work, the nitrogen K-edge X-ray absorption spectra were measured for pyridazine in the gas phase and in aqueous solution. The ultraviolet and X-ray absorption spectra of pyridazine in aqueous solution, as well as those in the gas phase, were then calculated with models based on the algebraic-diagrammatic construction through second order [ADC(2)] with the resolution-of-identity (RI) approximation and compared with the spectra obtained in experiments. For aqueous solution, explicit local solvation structures were extracted from an ab initio molecular dynamics (AIMD) trajectory of pyridazine in bulk water, and RI-ADC(2) was combined with the conductor-like screening model (COSMO). The experimental absorption spectra of pyridazine in aqueous solution were reproduced with good accuracy by theoretical treatment of an ensemble containing the explicit local solvation structures of pyridazine with relevant water molecules combined with the COSMO solvation model of water for long-range solvation.

Molecular dynamics simulation of extractive desulfurization of diesel oil model using magnetic ionic liquids

This paper serves as a molecular dynamics (MD) study on the desulfurization of diesel oil model using magnetic ionic liquids (MILs). In this regard, three different MILs, namely, [emim][FeCl4], [bmim][FeCl4] and [hmim][FeCl4] have been used to remove the dibenzothiophene (DBT) from n-dodecane as diesel oil model. The effects of alkyl chain length of cation in MIL, temperature, initial sulfur content and mass ratio of MIL to diesel oil on two vital parameters of desulfurization process i.e. percentage of S-removal and Nernst partition coefficient (KN) were investigated. These two parameters were calculated based on the method proposed by Feng and Mi (Ind. Eng. Chem. Res. 2014, 53, 20234-20240), in which they used the radial distribution function (RDF) plots obtained by Conductor-like Screening Model for Real Solvents (COSMO-RS) to evaluate the desulfurization of fuel oil, quantitatively. Our results showed that the [bmim][FeCl4] has the highest DBT-philisity and its S-removal efficiency increases with increasing temperature and the concentration of the MIL. Furthermore, from the investigation of the initial sulfur content in diesel oil model it is concluded that the MIL can be a good extractor for oil refinery applications with a wide range of sulfur content in diesel oil. The results of RDF and combined distribution function (CDF) plots and also Voronoi tessellation analysis showed that the DBT molecules are adsorbed mainly by the MIL molecules compared with the n-dodecane which leads to DBT-removal. Also, it is found that the DBT molecules interact with the cation of MIL more than its anion. The results of domain analysis showed that the n-dodecane subset is stiffer than the MIL and DBT subsets. Altogether, the Fe-containing MILs can be a good sulfur extractor with high S-removal efficiency, lower toxicity than common volatile organic solvents, and low cost compared to the other common methods such as hydrodesulfurization (HDS), for future oil refinery applications.

Theoretical insight into the conversion of glucose to 5-hydroxymethylfurfural in subcritical water

The reaction mechanism of the isomerization of glucose to fructose and further dehydration of fructose to 5-hydroxymethylfurfural (5-HMF) in subcritical water was investigated by the dispersion-corrected density functional theory (DFT-D) method with Dmol3 package in Materials Studio. The implicit solvent model was used to evaluate the bulk solvation under the conductor-like screening model (COSMO) approach, in which a dielectric constant (ɛ) of 27 was used to represent the subcritical water at 523.15 K. The explicit solvent model was adopted with a hybrid micro-solvation-continuum approach, to indicate the micro-solvation by explicit H2O molecules and the bulk solvation with ɛ = 27. The calculation results indicate that explicit H2O molecules participate in the reaction and catalytically promotes the proton transfer processes, suggesting that the explicit solvent model is preferable to the implicit solvent model to represent the conversion of 5-HMF in subcritical water. The isomerization of glucose to fructose is exothermic by 5.26 kcal/mol, where the isomerization of open-chain glucose to enol form is the rate-determining step, with the activation energy of 33.89 kcal/mol; the free energy of transition state configuration depends upon both the difficulty in α–H extraction of open-chain glucose and the stability of formed carbocation. In contrast, the hydration of fructose to 5-HMF is exothermic by 12.93 kcal/mol and the first hydration is the rate-determining step, with the activation energy of 50.59 kcal/mol; the free energy of transition state configuration is determined by the stability of carbocation formed by the dehydration of protonated OH group at C(2) site of fructose. This work discloses the promoting effect of Brønsted base on the isomerization of glucose to fructose and that of Brønsted acid on the dehydration of fructose to 5-HMF, which may provide certain clues to the modification of catalytic sites and the selection of solvent in the conversion of glucose to 5-HMF.

Computational Approach for Rapidly Predicting Temperature-Dependent Polymer Solubilities Using Molecular-Scale Models.

One promising approach to recycle multicomponent plastic waste (e. g., multilayer plastic films) is selective dissolution. Selective dissolution is a solvent-mediated process in which differences in polymer solubility in a carefully chosen solvent system are exploited to recover a target polymer. Here, a computational approach was developed that rapidly predicts temperature-dependent polymer solubilities to guide the design of solvent systems for solvent-mediated polymer recycling. Polymer conformations were obtained from molecular dynamics simulations by modeling the polymer as a short oligomer and then used as input to the conductor-like screening model for real solvents (COSMO-RS) for solubility predictions. Using polyethylene (PE) and ethylene vinyl alcohol (EVOH) as representative polymers, the effect of simulation parameters was systematically studied, and predicted solubilities were found to be in good agreement with experimental measurements. The applicability of the approach was demonstrated by identifying selective solvents for PE and EVOH dissolution from a library of 524 solvents.

Evaluation on Cocrystal Screening Methods and Synthesis of Multicomponent Crystals: A Case Study

Screening of suitable coformers is a major challenge during the development of cocrystals. To guide and simplify the cocrystal synthesis process, we evaluated three different predictive methods as well as their combinations during the cocrystallization of 2-amino-4,6-dimethoxypyrimidine (MOP) with 63 components. The conductor-like screening model for the real solvents (COSMO-RS) approach offered the best predictive results among three methods with an overall success rate of 84.1%. When combined with molecular complementarity (MC) analysis, the success rate was up to 85.7%. The Hansen solubility parameters (HSP) method did not deliver a satisfying outcome no matter if used individually or in combination for the MOP system. In addition, based on the screened results, 21 new solid phases of MOP were experimentally observed. Among them, the crystal structures of 10 multicomponent crystals (cocrystals and salts) were revealed by single crystal X-ray diffraction analysis (SCXRD), and their thermodynamic and spectroscopy properties were also characterized. The Hirshfeld surface analysis and the molecular electrostatic potential (MEP) surface analysis were conducted to explore the interactions in multicomponent crystals and the origin for salts and cocrystals. The cases in this study not only enriched the solid forms of MOP, evidenced the feasibility of the combined screening method, but also set an effective example for choosing potential coformers to prepare multicomponent crystals.

Experimental and Theoretical Study on Theobromine Solubility Enhancement in Binary Aqueous Solutions and Ternary Designed Solvents.

The solubility of theobromine was studied both experimentally and theoretically. The solubility was determined spectrophotometrically at 25 °C in neat organic solvents, aqueous binary mixtures, Natural Deep Eutectic Solvents (NADES) and ternary NADES mixtures with water. It was found that addition of water in unimolar proportions with some organic solvents increases theobromine solubility compared to neat solvents. Additionally, using NADES results in a solubility increase of the studied compound not only in relation to water but also DMSO. The addition of water (0.2 molar fraction) to NADES is responsible for an even larger increase of solubility. The measured solubilities were interpreted in terms of three theoretical frameworks. The first one—belonging to the set of data reduction techniques—proved to be very efficient in quantitative back-computations of excess solubility of theobromine in all studied systems. The default approach utilizing the well-recognized COSMO-RS (Conductor-like Screening Model for Real Solvents) framework offered at most a qualitative solubility description. The extended search for possible contacts provided evidence for the existence of many intermolecular complexes that alter the electron density of the solute molecule, thus influencing solubility computations. Taking into account such intermolecular contacts by using the COSMO-RS-DARE (Conductor-like Screening Model for Realistic Solvation-Dimerization, Aggregation, and Reaction Extension) framework seriously increased the accuracy of solubility computations.