Acetone-water Mixtures Research Articles

Kinetic and Mechanistic Aspects of Reactivity of the Oxidation of Some Fe(II)–Tris Schiff Base Complexes by Peroxydisulfate: Spectrophotometric Tracer and Solvent Effect on the Reactivity

ABSTRACTThe kinetics of the oxidation of some Fe(II)–Tris Schiff base complexes by peroxydisulfate was studied spectrophotometrically in the aqueous medium and in the organic–aqua binary mixture. The inspected complexes were derived from the condensation of 2‐acetylpyridine and substituted benzylamines. The oxidation reaction of the studied complexes was followed at 303 K under pseudo–first‐order conditions. It was found that the oxidation reaction by S2O82− consists of two steps. The first step is the formation of an ion pair from the reactants, and the second step is an electron transfer from the metal center to the peroxydisulfate oxidant, with an associated peroxo bond fissure. A mechanism, based on the experimental results, was proposed, and the rate law was derived. The effect of organic solvent on the reaction rate was studied in the presence of different ratios (v/v) of methanol–water and acetone–water mixtures. Moreover, the changes in the activation barrier from water to water–methanol and water–acetone mixtures were estimated from the kinetic data. The transfer chemical potentials of the initial and transition states from water into mixed solvents were determined from solubility measurements. Solvent effects on the reaction rate were discussed in terms of initial state versus transition state solvation.

Sterically hindered selenoether ligands: palladium(ii) complexes as catalytic activators for Suzuki–Miyaura coupling

2-Hydroxy/(benzyloxy)-3,5-di-tert-butyl benzaldehyde reacts with PhSeCH2CH2NH2 resulting in a sterically hindered selenoether ligand (Schiff base) [2–HO–3,5–(C(CH3)3)2–C6H2–CN–(CH2)2SePh] (L1)/[2–PhCH2O–3,5–(C(CH3)3)2–C6H2–CH2–NH–(CH2)2SePh] (L2). The reactions of L1 and L2 with Na2PdCl4 in methanol and acetone–water mixture at room temperature have resulted in complexes [PdCl (L1-H)] (1) and [PdCl2(L2)] (2)], respectively. Both the complexes and their ligands have been characterized with 1H, 13C{1H} and 77Se{1H} NMR spectroscopy. The molecular structures of complexes 1 and 2 have been determined with single crystal X-ray diffraction. The Pd–Se bond lengths in 1 and 2 are 2.370(1) and 2.366(1) A, respectively. The geometry around palladium in both the complexes is nearly square planar. Complexes 1 and 2 (0.1 mol% Pd) have been found efficient as catalysts for Suzuki–Miyaura C–C coupling reactions in the presence of K2CO3 in ethanol. The catalysis in water with complex 1 in the presence of K2CO3 was found feasible but with low conversion (up to 40%). The efficiency of 1 in carrying out the coupling is marginally better than that of 2.

Pretreatment of Japanese cedar by ionic liquid solutions in combination with acid and metal ion and its application to high solid loading.

BackgroundLignocellulosic biomass from plant biomass, especially softwoods, are well-known to present difficulties during attempts at hydrolysis due to their rigid structure. Pretreatment of lignocellulosic biomass with ionic liquids (ILs) is attractive as this requires to a low input of energy. However, IL pretreatment has the disadvantage of the presence of large amounts of water. Recently, it was reported that a small amount of acid has a positive effect on the degradation of biomass in IL with water. In this study the pretreatment of Japanese cedar, the most abundant softwood in Japan, was investigated using a combination of IL, acid and metal ions.ResultsFirst, the novel ionic liquid pretreatment was investigated by changing the pretreatment solvent and the anti-solvent. A mixture of IL, acid and ferric oxide (Fe3+) ion was most effective for pretreatment, and an acetone-water mixture was also most effective on the precipitation of biomass. These optimized pretreatment combinations attained a higher degree of glucose release from the pretreated biomass. The amount of cellulose was concentrated from to a level of 36 to 84% of the insoluble fraction by the optimized pretreatment. Based on this result, it was assumed that the extraction of the lignin fraction from the biomass into an anti-solvent solution was attained. Finally, this optimized pretreatment was applied to the enzymatic hydrolysis of Japanese cedar at high-solid biomass loading, and 110 g/L of glucose production was attained. In addition, the ethanol fermentation with this hydrolyzed solution by Saccharomyces cerevisiae achieved 50 g/L ethanol production, and this yield reached 90% of the theoretical yield.ConclusionsWe developed an effective pretreatment protocol by changing to a pretreatment solvent containing IL, acid, metal ion and anti-solvent. The optimized pretreatment has an effect on softwood and separately retrieved lignin as a by-product. The saccharified solution at high-solid biomass loading was converted to ethanol in a high yield. This proposed methodology would boost the performance of the bioconversion of low-cost materials to other chemicals, and would not be limited to only ethanol but also would include other target chemicals.

The study on the difference of the start-up and heat-transfer performance of the pulsating heat pipe with water−acetone mixtures

An experimental study was conducted to investigate the start-up and heat-transfer performance of a closed-loop pulsating heat pipe with water−acetone mixtures (at mixing ratios of 13:1, 4:1, 1:1, 1:4 and 1:13) and pure water and acetone under various filing ratios (35−70%) and heat inputs (10−100W). The closed-loop pulsating heat pipe was vertically placed and bottom-heated (i.e., heating wires were wrapped on the evaporation section) with inner and outer diameters of 2.0 and 4.0mm, respectively. It was observed that (1) compared with pure water, the pulsating heat pipe with water−acetone mixtures of mixing ratios of 13:1, 1:1, 1:4 and 1:13 possessed improved start-up performances, which could be initiated under a heat input of 10W and filling ratios of 35% and 45%. (2) Under low filling ratios (i.e., 35% and 45%), the pulsating heat pipe with water−acetone mixtures (i.e., at mixing ratios of 4:1, 1:1, 1:4 and 1:13) presented improved performance against the onset of dry-out conditions compared with PHPs using pure water and acetone. Under a heat input of 50W, the thermal resistances of the PHP with water–acetone mixtures (i.e., at mixing ratios of 4:1, 1:1, 1:4 and 1:13) decreased from 33.6% to 68.9% compared with pure working fluids. The addition of a fraction of pure water into pure acetone (e.g., the 13:1 water−acetone mixture) was found to be effective against dry-out. Conversely, adding a fraction of pure acetone into pure water (e.g., the 1:13 water−acetone mixture) did not prevent the onset of dry-out. (3) For high filling ratios (i.e., 62% and 70%) for which dry-out conditions are rarely encountered, the heat-transfer performances of the pulsating heat pipe with water−acetone mixtures (at mixing ratios of 13:1, 4:1, 1:1, 1:4 and 1:13) were not as efficient as that of the pulsating heat pipe with pure fluids. In contrast with the minima of mixtures under certain heat inputs, the maximum thermal resistances of pure water and acetone decreased by 45.8% and 38.7%, respectively.

Retracted: Acid‐Catalyzed Aquation of Ni(II)‐Hydrazone Complexes: Kinetics and Solvent Effect

ABSTRACTComplexes of the type [Ni(L)(H2O)]Cl2·nH2O, where L = 2‐pyridyl‐3‐isatinbishydrazone ligands, have been synthesized and characterized on the bases of elemental analysis, molar conductance, IR, electronic spectra, and thermal analysis (TGA and DTA). Acid‐catalyzed aquation of the Ni(II) isatin‐bishydrazone complexes was followed spectrophotometrically in various water–methanol and water–acetone mixtures at temperature 298 K. Kinetic behavior of the acid aquation is a linear rate law, indicating that the acid‐catalyzed aquation of these complexes in water–methanol and water–acetone mixtures follows a rate law with kobs = k2[H+]. The effect of the mole fraction of the ganic solvent, i.e., methanol and acetone, on the acid aquation has been analyzed; the decrease in the rate constant values with increasing of the methanol or acetone ratios is attributable to the effect of the co‐organic solvent on the initial states of the acid aquation by the destabilization of the H+ ion.

A Novel Alkali-Metal Hydrido-tris(pyrazolyl)borate (Tp*) Complex. Isolation and Crystal Structure of [(Me2CO)3(NaTp*)2

The title compound was isolated from the treatment of Tp*Sn(Cl)2Bu (1) with a large excess of sodium hydroxide in a mixture of acetone-water at room temperature. [(Me2CO)3(NaTp*)2] (2) crystallizes at 4 °C as prismatic colorless crystals, in the monoclinic space group P21/c with Z = 4, a = 12.2837(6), b = 24.3197(12), c = 16.9547(8) Å, β = 110.017(1)°, and V = 4759.0(4) Å3. The X-ray crystallographic analysis revealed a dinuclear unit in which two Tp*Na moieties are held together by three bridging acetone molecules acting as oxygen-based donors.

Kinetic study and reactivity trends of hydroxide ion attack on some chromen-2-one laser dyes in binary water-methanol and water-acetone mixtures

The kinetics of base-catalyzed hydrolysis of 7-dimethylamino-4-methyl-2H-chromen-2-one (DMAC) and 7-diethylamino-4-methyl-2H-chromen-2-one (DEAC) in binary water-methanol and water-acetone mixtures were studied in the temperature range from 288 to 313 K. The activation and thermodynamic parameters of these reactions were evaluated and discussed. The change in the activation energy in going from water to aqueous methanol and aqueous acetone was estimated from the kinetic data. Base-catalyzed hydrolysis of DMAC) and DEAC in aqueous methanol and aqueous acetone follows the first-order kinetic law with respect to hydroxide ion, k obs= k 2[OH]. The hydrolysis rate constants of DMAC and DEAC decrease as the fraction of methanol or acetone in the binary mixture rises, which is due to destabilization of OH− ion. The high negative entropies of activation support the proposed mechanism involving formation of an intermediate complex and reflect rigidity and stability of the latter. Opening of the pyran ring in the intermediate complex is the rate-determining step.

High-frequency electric conductivity of mixtures of water with acetone, dimethyl sulfoxide, and carbamide

The high-frequency (HF) electric conductivity (EC) of water-acetone, water-dimethyl sulfoxide (DMSO), and water-carbamide mixtures was analyzed. The limiting high-frequency conductivity decreased as the content of the organic component in the mixture increased. When the acetone and DMSO concentrations increased, the high-frequency conductivity passed through a maximum at 2450 MHz and increased with the carbamide concentration in its mixtures with water. The optimum conditions for the absorption of HF energy by the aqueous organic mixtures under study were determined.

Hydrophobicity and kinetic inspection of hydroxide ion attack on some chromen-2-one laser dyes in binary aqueous–methanol and aqueous–acetone mixtures: Initial state-transition state analysis

In the present study, reactivity base-catalyzed hydrolysis of 7-dimethylamino-4-methyl-2H-chromen-2-one (DMAC) and 7-diethylamino-4-methyl-2H-chromen-2-one (DEAC) in binary aqueous–methanol and aqueous–acetone mixtures was examined at 298K. Kinetic results, rate laws and reaction mechanisms were established. Moreover, the change in the activation energy barrier of the investigated compounds from water to water–methanol and water–acetone mixtures was estimated from the kinetic data. Base-catalyzed hydrolysis of (DMAC) and (DEAC) in aqueous–methanol and aqueous–acetone mixtures follows a rate law with kobs=k2[OH]. The decrease in the rate constants of (DMAC) and (DEAC) as the proportion of methanol and acetone is due to the destabilization of OH− ion. The solubilities of the studied compounds, DMAC and DEAC in water–methanol and water–acetone mixtures were established and their transfer chemical potentials were calculated. Solvent effect on reactivity trends of the investigated compounds has been analyzed into initial and transition state components by using the transfer chemical potentials of the reactants and the kinetic data of the studied compounds. The decrease in the observed rate constant values (kobs) of the base hydrolysis of DMAC and DEAC with increasing of methanol% or acetone% is dominated by the initial state (IS).

Pretreatment of Japanese cedar by ionic liquid solutions in combination with acid and metal ion and its application to high solid loading

Lignocellulosic biomass from plant biomass, especially softwoods, are well-known to present difficulties during attempts at hydrolysis due to their rigid structure. Pretreatment of lignocellulosic biomass with ionic liquids (ILs) is attractive as this requires to a low input of energy. However, IL pretreatment has the disadvantage of the presence of large amounts of water. Recently, it was reported that a small amount of acid has a positive effect on the degradation of biomass in IL with water. In this study the pretreatment of Japanese cedar, the most abundant softwood in Japan, was investigated using a combination of IL, acid and metal ions. First, the novel ionic liquid pretreatment was investigated by changing the pretreatment solvent and the anti-solvent. A mixture of IL, acid and ferric oxide (Fe3+) ion was most effective for pretreatment, and an acetone-water mixture was also most effective on the precipitation of biomass. These optimized pretreatment combinations attained a higher degree of glucose release from the pretreated biomass. The amount of cellulose was concentrated from to a level of 36 to 84% of the insoluble fraction by the optimized pretreatment. Based on this result, it was assumed that the extraction of the lignin fraction from the biomass into an anti-solvent solution was attained. Finally, this optimized pretreatment was applied to the enzymatic hydrolysis of Japanese cedar at high-solid biomass loading, and 110 g/L of glucose production was attained. In addition, the ethanol fermentation with this hydrolyzed solution by Saccharomyces cerevisiae achieved 50 g/L ethanol production, and this yield reached 90% of the theoretical yield. We developed an effective pretreatment protocol by changing to a pretreatment solvent containing IL, acid, metal ion and anti-solvent. The optimized pretreatment has an effect on softwood and separately retrieved lignin as a by-product. The saccharified solution at high-solid biomass loading was converted to ethanol in a high yield. This proposed methodology would boost the performance of the bioconversion of low-cost materials to other chemicals, and would not be limited to only ethanol but also would include other target chemicals.

Effects of Maytenus ilicifolia on reproduction and embryo-fetal development in Wistar rats.

Maytenus ilicifolia (Celastraceae), popularly known as espinheira-santa, is a native plant from the Atlantic forest and is commonly used in popular medicine to treat inflammation and as an abortifacient. To evaluate the effects of M. ilicifolia on pregnant rats during the organogenic period (T1) or throughout the gestational period (T2), an extract obtained using an acetone-water mixture at a 70:30 ratio was administered via gavage at a dose of 15.11 mg·kg(-1)·day(-1) over 2 treatment periods (T1 and T2). No clinical signs of maternal toxicity were observed. Term fetuses did not present malformations or anomalies as the number of implantations, reabsorptions, live, and dead fetuses were similar to the control group. In conclusion, M. ilicifolia hydroacetonic extract is non-toxic to pregnant rats and appears to not interfere with the progress of embryo-fetal development.

Gradient Structure‐Induced Temperature Responsiveness in Styrene/Methyl Methacrylate Gradient Copolymers Micelles

In this work, micelles are formed by gradient copolymer of styrene and methyl methacrylate in acetone-water mixture and their temperature responsiveness is investigated in a narrow range near room temperature. Three different kinds of structural transitions could be induced by temperature: unimers to micelle transition, shrinkage/stretching of micelles, and morphological transition from spherical micelles to vesicles. In addition, a model analysis on the interface of gradient copolymer micelle is made to better understand these phenomena. It is found that both position and composition of the interface could alter in response to the change in temperature. According to the experiments and model analysis, it is proposed that temperature responsiveness might be an intrinsic and universal property of gradient copolymer micelles, which only originates from the gradient structure.

Biosorptive distillations to purify isopropanol: improvements over the current process in terms of energy consumption and exergy

ABSTRACTThe removal of water from certain organic solvents via ordinary distillation requires several equilibrium stages if the organics are sufficiently concentrated, because the equilibrium curve for isopropanol–water is near the operating line, whereas acetone–water mixtures form a tangent pinch. In contrast, biosorption is only competitive when small quantities of adsorbate are removed. To overcome the drawbacks of both ordinary distillation and biosorption, a biosorptive distillation process was suggested for purifying 99.7 wt% isopropanol from a feed containing small amounts of water. Adsorption/regeneration experiments were conducted to investigate the breakthrough time and reusability of the adsorbent. The Ritchie equation, which fits the adsorption experimental data well, was embedded into the modified process simulation. Most of the water was removed via the adsorption part, which reduced its influence on the distillation. Compared to current commercial process, biosorptive distillation leads to a 25.4% reduction in the total energy and an overall exergy loss of 28.9% relative to absorbent regeneration. Furthermore, less than 1 year is required to recover the additional investment of the modified process. The proposed process can be both environmentally friendly and energy efficient. © 2013 Curtin University of Technology and John Wiley & Sons, Ltd.

Solvent–water extraction method for the evaluation of polycyclic aromatic hydrocarbons bioavailability in coal–tar-contaminated soils

A solvent–water extraction method was proposed as an assessment tool to estimate the bioavailability of polycyclic aromatic hydrocarbons in coal–tar-contaminated soils. The approach taken was to measure the percent of polycyclic aromatic hydrocarbons extracted by a solvent–water mixture and comparing the results with the percent of polycyclic aromatic hydrocarbons degraded in a soil slurry reactor. Five soil samples from three former manufactured gas plant sites and a coal–tar disposal site which were operated between 1880 and 1947, and 1945 and 1950, respectively, in Iowa, USA were used in this study. Extraction experiments were conducted using acetone–water or ethanol–water mixtures with solvent volume fractions ranging from 1.0 to 0.4 (v/v). The percent of polycyclic aromatic hydrocarbons extracted from the various soils decreased as the volume fraction of the solvent in the solvent–water mixture was reduced. An acetone–water mixture of 0.6 was found to be appropriate in correlating the percent of polycyclic aromatic hydrocarbons degraded to the percent of polycyclic aromatic hydrocarbons extracted. For the first correlation, the percent extracted and the percent biodegraded were modified by using the molecular weights and log K ow of polycyclic aromatic hydrocarbons, respectively. For the second correlation, the equation relating the percent extracted and the percent biodegraded was modified using soil properties such as organic carbon content and percent of clay and silt. Although the experiments were conducted for a limited number of soils, the extraction method appeared to be a good starting point in estimating the bioavailability of polycyclic aromatic hydrocarbons in coal–tar-contaminated soils.

Graphene for reducing bubble defects and enhancing mechanical properties of graphene/cellulose acetate composite films

In this study, we have demonstrated a strategy by which graphene was used to reduce the bubble defects and enhance the mechanical properties in graphene/cellulose acetate (Gr/CA) composite films. Mono- and multilayer graphene flakes were successfully prepared in the water–acetone mixtures by a jet cavitation method. Moreover, outstanding enhancement of mechanical properties of Gr/CA composite films were obtained at relatively low concentration of graphene flakes. Young’s modulus of these composite films increased linearly with the graphene flakes loading, due to the significantly high surface area of graphene and strong interactions between graphene flake and CA. Furthermore, three-dimensional channel formed by graphene flakes could increase the degassing speed and reduce the negative effects of bubbles. The Gr/CA composite has excellent mechanical properties and, more importantly, it is a natural and environmentally friendly polymer composite.

Solubility of ammonium oxalate in water–acetone mixtures and metastable zone width of their solutions

Experimental results on the solubility c of ammonium oxalate in mixed water–acetone solvents containing acetone content x<0.55 by weight at different saturation temperature T are presented and discussed using the theory of regular solutions. It was found that: (1) the dependence of the solubility c of ammonium oxalate in solutions of different mixed water–acetone solvents on temperature T follows an Arrhenius-type relation, (2) the dependence of c on acetone content x at different temperature T follows the relation: ln(c+δ)=a−bx, where the parameters a and b are measures of deviation of a solution from ideality and the correction factor δ is related to the activity coefficient fa of the solution, which decreases with an increase in c, and (3) the dependence of the solubility c of ammonium oxalate in solutions of different compositions x of water–acetone mixtures is related to the dielectric constant ɛ* of the solvent mixture, following the relation lnc=C+C1ɛ*, where C and C1 are related to the parameters a and b, respectively. Study of the metastable zone width, defined as maximum undercooling ΔTmax a solution saturated at a particular temperature T can withstand, of some selected solutions of mixed water–acetone solvents at different T revealed that ΔTmax decreases with an increase in antisolvent content x. The results are discussed using the self-consistent Nývlt-like approach.

Preferential solvation and association constants of 2-exo and 2-endo norbornyl chlorides in water–acetone mixtures

Molecular dynamics simulations of 2-exo and 2-endo norbornyl chlorides are performed in water–acetone mixtures to investigate the role of preferential solvation on the dissociation process of norbornyl chlorides. Increase in the association constants between carbon (C2) and chloride (Cl) of norbornyl chlorides with an increase in mole fraction of acetone supports the experimental data for the corresponding decrease in the rates of solvolysis for both exo and endo norbornyl chlorides. When the mole fraction of water is increased in water–acetone mixtures, acetone molecules are replaced by water molecules around C2 as well as Cl of norbornyl chloride. Preferential solvation by water is analysed using running coordination numbers and excess coordination numbers around C2 and Cl.

Novel, Calibration-Free Strategies for Supersaturation Control in Antisolvent Crystallization Processes

In-situ attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy and focused-beam reflectance measurement (FBRM) were used to monitor and control the antisolvent crystallization of paracetamol from an acetone–water mixture, which was conducted in a 150 mL flat bottom crystallizer with a Mettler Toledo Easymax Reactor system. Following the monitoring of a series of unseeded and seeded crystallization experiments using a constant addition rate of antisolvent, a simple calculation method for the set point of antisolvent addition rate, to maintain constant supersaturation via ATR-FTIR, was developed and implemented for feedback control of unseeded and seeded crystallizations. The implemented technique used a single peak in the ATR-FTIR spectral region without any calibration to effectively maintain supersaturation to a prespecified set point. By developing a solubility curve in terms of peak height and knowing key information of the process at any given time, the addition rate of antisol...

Estimation of Abamectin Residues Present in Tea: High-Performance Liquid Chromatography Technique

A simple, reliable, and sensitive method was based on high-performance liquid chromatography (HPLC) was developed and validated for the estimation of abamectin residues present in tea. The abamectin residues extracted with acetone-water mixture (70 : 30, v/v) and derivatised with 1-methylimidazole (1-MIM) and trifluoroacetic anhydride (TFAA) were estimated by HPLC using fluorescence detector (FLD). The technique was validated in terms of linearity, precision, recovery, specificity, limit of detection (LOD), and limit of quantification (LOQ). A good linear relationship () was absorbed in the abamectin concentration range from 0.01 to 1.0 μg mL−1. The limit of detection and limit of quantification of the method were 0.01 and 0.02 μg g−1, respectively. The average recoveries of the pesticide from black tea and dried green leaves ranged from 83.3 to 103.8% and 83.8 to 98.0%, respectively.

Kinetics, reactivity, initial-transition state analysis and thermodynamic parameters of base-catalyzed hydrolysis of coumalic acid in solvents with different polarities

Base-catalyzed hydrolysis of coumalic acid (COU) in binary aqueous-methanol and aqueous-acetone mixtures has been studied kinetically at a temperature range from 283 to 313K. Moreover, the change in the activation energy barrier of COU from water to water–methanol and water–acetone mixtures is estimated from the kinetic data. Solvent effects on reactivity trends have been analyzed into initial and transition state components by using transfer chemical potentials of the reactants and kinetic data. The transfer chemical potentials δmμθ for COU− anion are derived from solubility data from its calcium, cerium and lanthanum salts. The decrease in rate constant of the base hydrolysis reaction of COU as the percentage of methanol or acetone increases is dominated by transition state (TS). The base hydrolysis reaction of COU follows a rate law with kobs=k2[OH−] and the reaction mechanism was suggested. The high negative values of entropy of activation support the proposal mechanism, i.e. the investigated reaction takes place via the formation of an intermediate complex. Thus, the ring opening of the intermediate complex would be the rate controlling step.