RESUMEN
Fe(II) is of great importance in iron-based advanced oxidation processes. However, traditional methods to maintain Fe(II) concentration, such as the addition of chelating agents or reducing agents, may lead to an increase in chemical oxygen demand of secondary pollution. Therefore, in this study, iron sulfides, namely ferrous sulfide (FeS), pyrite (FeS2), and sulfidated nanoscale zero-valent iron (S-nZVI), were applied for not only the regeneration of Fe(II) but also the direct dissolution of Fe(II). Nanoscale calcium peroxide (nCaO2) was synthesized and used as the oxidant. The removal of 1,2-dichloroethane (1,2-DCA) were significantly promoted from 8.8 to 98.2, 79.2, and 80.8% with the aid of FeS, FeS2, and S-nZVI within 180 min, respectively. The dominant reactive oxygen species were demonstrated and their steady-state concentrations were quantified. Besides, the dechlorination of 1,2-DCA reached 90.4, 69.5, and 83.9% in nCaO2/Fe(III) systems coupled with FeS, FeS2, and S-nZVI, respectively. All three systems had high tolerance to the complex water conditions, of which FeS-enhanced nCaO2/Fe(III) system displayed the best performance, which could be recommended to put into practice for the remediation of 1,2-DCA contaminated groundwater.
Asunto(s)
Dicloruros de Etileno , Hierro , Peróxidos , Sulfuros , Contaminantes Químicos del Agua , Dicloruros de Etileno/química , Peróxidos/química , Sulfuros/química , Hierro/química , Contaminantes Químicos del Agua/química , Compuestos Férricos/química , Purificación del Agua/métodos , Compuestos FerrososRESUMEN
The compound 1,2-dichloroethane (1,2-DCA), a persistent and ubiquitous pollutant, is often found in groundwater and can strongly affect the ecological environment. However, the extreme bio-impedance of C-Cl bonds means that a high energy input is needed to drive biological dechlorination. Biotechnology techniques based on microbial photoelectrochemical cell (MPEC) could potentially convert solar energy into electricity and significantly reduce the external energy inputs currently needed to treat 1,2-DCA. However, low electricity-generating efficiency at the anode and sluggish bioreaction kinetics at the cathode limit the application of MPEC. In this study, a g-C3N4/Blue TiO2-NTA photoanode was fabricated and incorporated into an MPEC for 1,2-DCA removal. Optimal performance was achieved when Blue TiO2 nanotube arrays (Blue TiO2-NTA) were loaded with graphitic carbon nitride (g-C3N4) 10 times. The photocurrent density of the g-C3N4/Blue TiO2-NTA composite electrode was 2.48-fold higher than that of the pure Blue TiO2-NTA electrode under light irradiation. Furthermore, the MPEC equipped with g-C3N4/Blue TiO2-NTA improved 1,2-DCA removal efficiency by 45.21% compared to the Blue TiO2-NTA alone, which is comparable to that of a microbial electrolysis cell. In the modified MPEC, the current efficiency reached 69.07% when the light intensity was 150 mW cm-2 and the 1,2-DCA concentration was 4.4 mM. The excellent performance of the novel MPEC was attributed to the efficient direct electron transfer process and the abundant dechlorinators and electroactive bacteria. These results provide a sustainable and cost-effective strategy to improve 1,2-DCA treatment using a biocathode driven by a photoanode.
Asunto(s)
Electrodos , Dicloruros de Etileno , Nanotubos , Titanio , Contaminantes Químicos del Agua , Titanio/química , Nanotubos/química , Dicloruros de Etileno/química , Contaminantes Químicos del Agua/química , Contaminantes Químicos del Agua/metabolismo , Grafito/química , Nitrilos/química , Compuestos de Nitrógeno/química , Fuentes de Energía Bioeléctrica , Técnicas Electroquímicas/métodosRESUMEN
In 1932, Mizushima and Higasi reported the dependence of the dipole moments of 1,2-dichloroethane on both temperature and solvent in the Proceedings of the Imperial Academy, Japan. This report was followed by their first proposal of the existence of conformers that exchanged by internal rotation about a C-C single bond based on experimental data. Their monumental work marked the beginning of the essential concept of conformation in modern stereochemistry. Their proposal was later confirmed by the direct observation of the anti and gauche conformers of 1,2-dichloroethane by Raman spectroscopy, and further supported by other experimental and theoretical methods. The relative stabilities of the anti and gauche conformers of 1,2-dichloroethane and other 1,2-disubstituted ethanes were discussed in terms of steric, electrostatic, and stereoelectronic effects based on analysis of calculated data. Those studies influenced the development of subsequent research in organic chemistry, such as the conformational analysis of cyclohexane derivatives and the isolation of chiral gauche conformers.
Asunto(s)
Dicloruros de Etileno , Espectrometría Raman , Conformación Molecular , Dicloruros de Etileno/química , TemperaturaRESUMEN
Crystal engineering of metal oxide supports represents an emerging strategy to improve the catalytic performance of noble metal catalysts in catalytic oxidation of chlorinated volatile organic compounds (CVOCs). Herein, Pt catalysts on a TiO2 support with different crystal phases (rutile, anatase, and mixed phase (P25)) were prepared for catalytic oxidation of 1,2-dichloroethane (DCE). The Pt catalyst on P25-TiO2 (Pt/TiO2-P) showed optimal activity, selectivity, and stability, even under high-space velocity and humidity conditions. Due to the strong interaction between Pt and P25-TiO2 originating from the more lattice defects of TiO2, the Pt/TiO2-P catalyst possessed stable Pt0 and Pt2+ species during DCE oxidation and superior redox property, resulting in high activity and stability. Furthermore, the Pt/TiO2-P catalyst possessed abundant hydroxyl groups, which prompted the removal of chlorine species in the form of HCl and significantly decreased the selectivity of vinyl chloride (VC) as the main byproduct. On the other hand, the Pt/TiO2-P catalyst exhibited a different reaction path, in which the hydroxyl groups on its surface activated DCE to form VC and enolic species, besides the lattice oxygen of TiO2 for the Pt catalysts on rutile and anatase TiO2. This work provides guidance for the rational design of catalysts for CVOCs.
Asunto(s)
Titanio , Cloruro de Vinilo , Titanio/química , Oxidación-Reducción , Dicloruros de Etileno/químicaRESUMEN
Charge (ion and electron)-transfer reactions at a liquid/liquid interface are critical processes in many important biological and chemical systems. An ion-transfer (IT) process is usually very fast, making it difficult to accurately measure its kinetic parameters. Nano-liquid/liquid interfaces supported at nanopipettes are advantageous approaches to study the kinetics of such ultrafast IT processes due to their high mass transport rate. However, correct measurements of IT kinetic parameters at nanointerfaces supported at nanopipettes are inhibited by a lack of knowledge of the nanometer-sized interface geometry, influence of the electric double layer, wall charge polarity, etc. Herein, we propose a new electrochemical characterization equation for nanopipettes and make a suggestion on the shape of a nano-water/1,2-dichloroethane (nano-W/DCE) interface based on the characterization and calculation results. A theoretical model based on the Poisson-Nernst-Planck equation was applied to systematically study how the electric double layer influences the IT process of cations (TMA+, TEA+, TPrA+, ACh+) and anions (ClO4-, SCN-, PF6-, BF4-) at the nano-W/DCE interface. The relationships between the wall charge conditions and distribution of concentration and potential inside the nanopipette revealed that the measured standard rate constant (k0) was enhanced when the polarity of the ionic species was opposite to the pipette wall charge and reduced when the same. This work lays the right foundation to obtain the kinetics at the nano-liquid/liquid interfaces.
Asunto(s)
Dicloruros de Etileno , Aniones , Cationes , Dicloruros de Etileno/química , Cinética , Electricidad EstáticaRESUMEN
Spontaneous S-alkylation of methimazole (1) with 1,2-dichloroethane (DCE) into 1,2-bis[(1-methyl-1H-imidazole-2-yl)thio]ethane (2), that we have described recently, opened the question about its formation pathway(s). Results of the synthetic, NMR spectroscopic, crystallographic and computational studies suggest that, under given conditions, 2 is obtained by direct attack of 1 on the chloroethyl derivative 2-[(chloroethyl)thio]-1-methyl-1H-imidazole (3), rather than through the isolated stable thiiranium ion isomer, i.e., 7-methyl-2H, 3H, 7H-imidazo[2,1-b]thiazol-4-ium chloride (4a, orthorhombic, space group Pnma), or in analogy with similar reactions, through postulated, but unproven intermediate thiiranium ion 5. Furthermore, in the reaction with 1, 4a prefers isomerization to the N-chloroethyl derivative, 1-chloroethyl-2,3-dihydro-3-methyl-1H-imidazole-2-thione (7), rather than alkylation to 2, while 7 further reacts with 1 to form 3-methyl-1-[(1-methyl-imidazole-2-yl)thioethyl]-1H-imidazole-2-thione (8, monoclinic, space group P 21/c). Additionally, during the isomerization of 3, the postulated intermediate thiiranium ion 5 was not detected by chromatographic and spectroscopic methods, nor by trapping with AgBF4. However, trapping resulted in the formation of the silver complex of compound 3, i.e., bis-{2-[(chloroethyl)thio]-1-methyl-1H-imidazole}-silver(I)tetrafluoroborate (6, monoclinic, space group P 21/c), which cyclized upon heating at 80 °C to 7-methyl-2H, 3H, 7H-imidazo[2,1-b]thiazol-4-ium tetrafluoroborate (4b, monoclinic, space group P 21/c). Finally, we observed thermal isomerization of both 2 and 2,3-dihydro-3-methyl-1-[(1-methyl-1H-imidazole-2-yl)thioethyl]-1H-imidazole-2-thione (8), into 1,2-bis(2,3-dihydro-3-methyl-1H-imidazole-2-thione-1-yl)ethane (9), which confirmed their structures.
Asunto(s)
Dicloruros de Etileno/química , Metimazol/química , Alquilación , Cristalografía por Rayos X/métodos , Espectroscopía de Resonancia Magnética/métodos , Plata/químicaRESUMEN
Enzymes play a fundamental role in many biological processes. We present a theoretical approach to investigate the catalytic power of the haloalkane dehalogenase reaction with 1,2-dichloroethane. By removing the three main active-site residues one by one from haloalkane dehalogenase, we found two reactive descriptors: one descriptor is the distance difference between the breaking bond and the forming bond, and the other is the charge difference between the transition state and the reactant complex. Both descriptors scale linearly with the reactive barriers, with the three-residue case having the smallest barrier and the zero-residue case having the largest. The results demonstrate that, as the number of residues increases, the catalytic power increases. The predicted free energy barriers using the two descriptors of this reaction in water are 23.1 and 24.2 kcal/mol, both larger than the ones with any residues, indicating that the water solvent hinders the reactivity. Both predicted barrier heights agree well with the calculated one at 25.2 kcal/mol using a quantum mechanics and molecular dynamics approach, and also agree well with the experimental result at 26.0 kcal/mol. This study shows that reactive descriptors can also be used to describe and predict the catalytic performance for enzyme catalysis.
Asunto(s)
Dicloruros de Etileno/química , Dicloruros de Etileno/farmacología , Hidrolasas/química , Hidrolasas/metabolismo , Algoritmos , Catálisis , Activación Enzimática/efectos de los fármacos , Modelos Químicos , Conformación Molecular , Simulación del Acoplamiento Molecular , Simulación de Dinámica Molecular , Teoría Cuántica , Relación Estructura-ActividadRESUMEN
Reactivity at phase boundaries is central to many areas of chemistry, from synthesis to heterogeneous catalysis. New tools are necessary to gain a more detailed understanding of processes occurring at these boundaries. We describe a series of experiments to visualize phase boundaries using electrogenerated chemiluminescence (ECL) on glassy carbon electrodes. By taking advantage of the solubilities of the ECL luminophore and the coreactant in different liquid phases, we demonstrate that the interface of various phases (i.e., the boundaries formed between a water microdroplet, 1,2-dichloroethane, and a glassy carbon electrode and the boundaries formed between an oxygen bubble, water, and a glassy carbon electrode) can be evaluated. We measured microdroplet contact radii, the three-phase boundary thickness, and growth dynamics of electrogenerated O2 bubbles. These experimental tools and the fundamental knowledge they yield will find applications in biology, nanoscience, synthesis, and energy storage and conversion, where understanding phase boundary chemistry is essential.
Asunto(s)
Carbono/química , Dicloruros de Etileno/química , Oxígeno/química , Agua/química , Complejos de Coordinación/química , Técnicas Electroquímicas/instrumentación , Técnicas Electroquímicas/métodos , Electrodos , Luminiscencia , Sustancias Luminiscentes/química , Rutenio/química , Propiedades de SuperficieRESUMEN
A one-pot, three-component synthesis of benzimidazole-linked thiazolidines from 2-cyanomethyl benzimidazole, iso-, isothio-, or isoselenocyanates and 1,2-dichloroethane is reported. Isolation of the key intermediate formed during the course of the reaction validates its mechanistic pathway. Under the same reaction conditions, benzimidazole-linked/fused thiazinanes were obtained when 1,3-dichloropropane or diiodomethane was used.
Asunto(s)
Bencimidazoles/síntesis química , Benzotiazoles/síntesis química , Tiazolidinas/síntesis química , Dicloruros de Etileno/química , Hidrocarburos Yodados/química , Compuestos de Organoselenio/química , Propano/análogos & derivados , Propano/químicaRESUMEN
Metal-organic frameworks (MOFs) have received significant attention as promising precursors or sacrificial templates in the preparation of porous carbon supported catalysts. In this study, N-doped porous carbon supported Ni catalysts (denoted as Ni/NC) were prepared using furfuryl alcohol (FA) loaded Ni-MOF-74 as the precursor followed by NH4OH treatment and pyrolysis under N2 atmosphere. For comparison purpose, Ni catalysts supported on porous carbon (denoted as Ni/C) were also prepared by direct pyrolysis of Ni-MOF-74. The selective gas phase catalytic hydrodechlorination of 1,2-dichloroethane to ethylene was carried out to evaluate the catalytic performances of the catalysts. It was found that for Ni catalysts prepared at the same pyrolysis temperature, Ni particle sizes in Ni/NC catalysts were significantly smaller (20-40% smaller) than that of Ni/C. This reflected that pre-modification of Ni-MOF-74 using FA and NH4OH could effectively increase Ni dispersion in Ni catalysts derived from Ni-MOF-74. Moreover, Ni/NC had a markedly stronger ability to form spillover H2 owing to the enhanced metal-support interactions by N-doping. Accordingly, Ni/NC catalysts exhibited much higher catalytic activities than Ni/C catalysts. The turnover frequencies of Ni/NC catalysts were found to be 1.22-1.65 times higher than Ni/C catalysts. Increasing pyrolysis temperature led to decreased catalytic activities of both Ni/C and Ni/NC catalysts, due to the aggregation of Ni particles at higher treatment temperature. The findings from this study demonstrate that the MOF-mediated synthesis method offers a promising way to prepare Ni-based catalysts for catalytic hydrodechlorination of chlorinated hydrocarbons.
Asunto(s)
Carbono/química , Dicloruros de Etileno/química , Etilenos/química , Catálisis , Furanos , Tamaño de la Partícula , Porosidad , TemperaturaRESUMEN
In this paper, the electrochemical behavior of four fluoroquinolone antibiotics (FAs) [Ciprofloxacin (Cip), Enrofloxacin (Enr), Marbofloxacin (Mar) and Ofloxacin (Ofl)] at a polarized interface between two immiscible electrolyte solutions (ITIES) has been studied using ion-transfer voltammetry (ITV). The measurements were conducted in the traditional macroscopic (macro-ITIES) and a recently developed miniaturized (micro-ITIES) platform. The latter was obtained from fused silica micro-capillaries having an internal diameter of 25⯵m. We used macroITIES to obtain a number of analytical parameters such as: standard Galvani potential of ion transfer (ΔΦ0), diffusion coefficients (D), free Gibbs energy of ion transfer (ΔG0) and partition coefficients (logPDCE). The latter were compared with the available literature values of logPoctanol. The effect of concentration of the studied antibiotics on the electrochemical response was investigated with the microITIES platform, setting statistical parameters such as: linear dynamic ranges (LDRs - studied from 1⯵M up to 50⯵M), lower limit of detections (LODs - around 1⯵M) and sensitivity (found in the range from 2.6·10-2 to 6.8·10-2â¯nA·µM-). MicroITIES were further used to study the effect of pH on the analytical signal and the results are plotted in a form of ion partition diagrams. Working with microITIES supported with the fused silica capillaries significantly reduced the volumes of consumed chemicals and expedite all analytical experiments. The provided results can be successfully applied in pharmacology and electroanalysis for testing and determination of the chosen fluoroquinolone antibiotics.
Asunto(s)
Antibacterianos/análisis , Técnicas Electroquímicas , Dicloruros de Etileno/química , Fluoroquinolonas/análisis , Agua/química , Transporte Iónico , Estructura MolecularRESUMEN
1,2-Dichloroethane is one of the most hazardous environmental pollutants in wastewaters. It is mainly used to produce vinyl chloride monomer, the major precursor for PVC production. It is determined to be a probable human carcinogen and has been listed as a priority pollutant by the United States Environmental Protection Agency. Due to high chemical stability and low biodegradability of 1,2-dichloroethane, heterogeneous photocatalysis was used for degradation of this chlorinated hydrocarbon. PAni-TiO2 nanocomposite was synthesized by in situ deposition oxidative polymerization method and immobilized on glass beads by a modified dip coating and heat attachment method. The characteristics of synthesized PAni-TiO2 nanoparticles were confirmed using the results of morphology tests including Fourier-transform infrared spectra, X-ray diffraction patterns, particle size analysis, UV-Visible spectrophotometer, scanning electron microscope, and energy-dispersive X-ray spectroscopy. The performance of photocatalytic degradation of 1,2-dichloroethane using synthesized PAni-TiO2 nanocomposite in a designed and constructed pilot scale packed bed recirculating photocatalytic reactor under xenon light irradiation was investigated. The response surface methodology based on the central composite design was used to evaluate and optimize the effect of 1,2-dichloroethane concentration, residence time, pH, and coating mass as independent variables on the photocatalytic degradation of 1,2-dichloroethane as the response function. Results showed that actual and predicted results were well fitted with R2 of 0.9870, adjusted R2 of 0.9718, and predicted R2 of 0.9422. The optimum conditions for 1,2-dichloroethane photocatalytic degradation were the 1,2-dichloroethane concentration of 250 mg/L, the residence time of 240 min, pH of 5, and coating mass of 0.5 mg/cm2, which resulted in 88.84% photocatalytic degradation. Kinetic of the photocatalytic degradation at optimal condition follows the Langmuir-Hinshelwood first-order reaction with k = 0.0095 min-1 with R2 = 0.9455. Complete photocatalytic degradation of 1,2-DCE was achieved after 360 min.
Asunto(s)
Dicloruros de Etileno/química , Nanopartículas/química , Titanio/química , Catálisis , Concentración de Iones de Hidrógeno , Luz , Microscopía Electrónica de Rastreo , Oxidación-Reducción , Tamaño de la Partícula , Espectrometría por Rayos X , Espectrofotometría Ultravioleta , Eliminación de Residuos Líquidos/instrumentación , Aguas Residuales/química , Contaminantes Químicos del Agua/química , Difracción de Rayos XRESUMEN
Flurbiprofen is a kind of nonsteroidal anti-inflammatory drug, which has been widely used in clinic for treatment of rheumatoid arthritis and osteoarthritis. It has been reported that S-flurbiprofen shows good performance on clinic anti-inflammatory treatment, while R-enantiomer almost has no pharmacological activities. It has important practical values to obtain optically pure S-flurbiprofen. In this work, chiral ionic liquids, which have good structural designability and chiral recognize ability, were selected as the extraction selector by the assistance of quantum chemistry calculations. The distribution behaviors of flurbiprofen enantiomers were investigated in the extraction system, which was composed of organic solvent and aqueous phase containing chiral ionic liquid. The results show that maximum enantioselectivity up to 1.20 was attained at pH 2.0, 25°C using 1,2-dichloroethane as organic solvent, 1-butyl-3-methylimidazole L-tryptophan ([Bmim][L-trp]) as chiral selector. The racemic flurbiprofen initial concentration was 0.2 mmol L-1 , and [Bmim][L-trp] concentration was 0.02 mol L-1 . Furthermore, the recycle of chiral ionic liquids has been achieved by reverse extraction process of the aqueous phase with chiral selector, which is significant for industrial application of chiral ionic liquids and scale-up of the extraction process.
Asunto(s)
Flurbiprofeno/química , Flurbiprofeno/aislamiento & purificación , Extracción Líquido-Líquido/métodos , Antiinflamatorios no Esteroideos/química , Antiinflamatorios no Esteroideos/aislamiento & purificación , Dicloruros de Etileno/química , Concentración de Iones de Hidrógeno , Líquidos Iónicos/química , Teoría Cuántica , Programas Informáticos , Solventes/química , EstereoisomerismoRESUMEN
Volatile chlorinated hydrocarbons (VCHs) are often found as a type of persistent and ubiquitous contaminant in groundwater. The feasibility, characteristics and microbial mechanism of acclimation of biodiversity-rich inoculation source for bioelectrochemical stimulated VCH dechlorination remain poorly understood. Here, the superior bioelectrochemical catalytic activities were observed for tetrachloroethylene (0.26â¯mMâ¯d-1) and 1,2-dichloroethane (2.20â¯mMâ¯d-1) dechlorination in anaerobic sludge-acclimated biocathodes with an optimal potential of -0.5â¯V, averaging 1.60-2.71 times higher than those reported in previous works on biocathodes. When the cathode was applied as the sole electron donor for dechlorination, columbic efficiencies reached the values greater than 80%. Tetrachloroethylene dechlorination showed a metabolic pathway with cis-1,2-dichloroethene as the main product, whereas 1,2-dichloroethane was dechlorinated entirely to the nontoxic ethene. The cathodic biofilms were highly abundant with the dechlorination and electro-active genera, while significant bacterial consortium variation was observed in response to the different VCH types and changes in cathodic potential. Bacillus, Pseudomonas and Lactococcus were mostly enriched for tetrachloroethylene dechlorination, and pceA, tceA and omcX were highly expressed. Geobacter was the most predominant during 1,2-dichloroethane dechlorination with rdhA, tceA and omcX highly expressed. In addition, although the impact of cathodic potentials was weaker than that of VCH types, the lower cathodic potentials, the more abundant of the electrode respiring populations and the higher expression of extracellular electron transfer related gene. This study demonstrated the great potential of acclimation of anaerobic sludge by electrical stimulation for accelerating VCH remediations and gave insights into its working molecular mechanisms.
Asunto(s)
Aclimatación , Biodegradación Ambiental , Técnicas Electroquímicas/métodos , Dicloruros de Etileno/química , Aguas del Alcantarillado/microbiología , Tetracloroetileno/química , Bacterias/metabolismo , Proteínas Bacterianas/metabolismo , Biopelículas , Electrodos , Hidrocarburos Clorados/química , Hidrocarburos Clorados/metabolismo , Tetracloroetileno/metabolismoRESUMEN
Although the application of 1,2-dichloroethane (DCE) as a chlorinating reagent in organic synthesis with the concomitant release of vinyl chloride as a useful byproduct is a fantastic idea, it still presents a tremendous challenge and has not yet been achieved because of the harsh dehydrochlorination conditions and the sluggish C-H chlorination process. Here we report a bifunctional electrocatalysis strategy for the catalytic dehydrochlorination of DCE at the cathode simultaneously with anodic oxidative aromatic chlorination using the released HCl as the chloride source for the efficient synthesis of value-added (hetero)aryl chlorides. The mildness and practicality of the protocol was further demonstrated by the efficient late-stage chlorination of bioactive molecules.
Asunto(s)
Técnicas Electroquímicas , Dicloruros de Etileno/química , Hidrocarburos Clorados/síntesis química , Platino (Metal)/química , Catálisis , Electrodos , Hidrocarburos Clorados/químicaRESUMEN
Rational enzyme design presents a major challenge that has not been overcome by computational approaches. One of the key challenges is the difficulty in assessing the magnitude of the maximum possible catalytic activity. In an attempt to overcome this challenge, we introduce a strategy that takes an active enzyme (assuming that its activity is close to the maximum possible activity), design mutations that reduce the catalytic activity, and then try to restore that catalysis by mutating other residues. Here we take as a test case the enzyme haloalkane dehalogenase (DhlA), with a 1,2-dichloroethane substrate. We start by demonstrating our ability to reproduce the results of single mutations. Next, we design mutations that reduce the enzyme activity and finally design double mutations that are aimed at restoring the activity. Using the computational predictions as a guide, we conduct an experimental study that confirms our prediction in one case and leads to inconclusive results in another case with 1,2-dichloroethane as substrate. Interestingly, one of our predicted double mutants catalyzes dehalogenation of 1,2-dibromoethane more efficiently than the wild-type enzyme.
Asunto(s)
Simulación por Computador , Dicloruros de Etileno/química , Hidrolasas/química , Modelos Químicos , Modelos Moleculares , Dominio Catalítico , Especificidad por SustratoRESUMEN
A series of Nb-doped (Ce,Cr)xO2-Nb2O5 mixed oxides with varying (Ce,Cr)xO2/Nb2O5 mass ratio were prepared by a co-precipitation method and evaluated for the catalytic performance of eliminating 1,2-dichloroethane (DCE). The results indicate that there exists a strong synergistic effect between acid sites and redox species in (Ce,Cr)xO2-Nb2O5 improving the catalytic activity for DCE oxidation. Appropriate Nb doping could promote the high dispersion and the interaction of metal oxides in the (Ce,Cr)xO2-Nb2O5 catalysts, resulting in the formation of more Cr6+ species with strong oxidizing ability and excellent mobility of oxygen species from bulk to surface to create more active sites for DCE deep oxidation. The (Ce,Cr)xO2-Nb2O5 catalysts with (Ce,Cr)xO2/Nb2O5 ratios of 2/1~1/2 exhibit excellent catalytic activity and durability for DCE degradation in dry air as well as benzene or water vapor, and less chlorinated byproduct is produced during the degradation of DCE.
Asunto(s)
Cerio/química , Cromo/química , Dicloruros de Etileno/química , Niobio/química , Óxidos/química , Catálisis , Oxidación-ReducciónRESUMEN
Plan B: 1,2-Dichloroethane was recently subject to regulatory controls in the European Union that will severely limit its commercial use. The practitioners of innovative synthetic methods, particularly C-H bond activation, need to investigate alternative solvents if their chemistry is to stay relevant.
Asunto(s)
Dicloruros de Etileno/química , Solventes/químicaRESUMEN
Interface between two immiscible electrolyte solutions (ITIES) supported on the orifice of a pipet have become a powerful platform to detect a broad range of analytes. We present here the detection of γ-aminobutyric acid (GABA) with the nanoITIES pipet electrodes for the first time. GABA has a net charge of zero in an aqueous solution at pH ≈ 7, and it has not previously been detected at ITIES. In this work, we demonstrated GABA detection at ITIES in an aqueous solution at pH ≈ 7, where we introduced a novel detection strategy based on "pH modulation from the oil phase". To the best of our knowledge, this is the first report of such. Current increases linearly with increasing concentrations of GABA, ranging from 0.25 mM to 1.0 mM. The measured half-wave transfer potential of GABA is -0.401 ± 0.010 V ( n = 22) vs E1/2,TBA. The measured diffusion coefficient for GABA detection at nanoITIES pipet electrode is 6.09 (±0.58) × 10-10 m2/s ( n = 5). Experimental results indicate that protons generated from octanoic acid dissociation in the oil phase do not come out from the oil phase into the aqueous phase; neither were protons produced in the aqueous phase. NanoITIES pipet electrodes with radii of 320-340 nm were used in the current study. This new strategy and knowledge presented here lays the groundwork for the future development of ITIES pipet electrodes, especially for the detection of electrochemically nonredox active analytes.
Asunto(s)
Caprilatos/química , Técnicas Electroquímicas/instrumentación , Dicloruros de Etileno/química , Agua/química , Ácido gamma-Aminobutírico/análisis , Técnicas Electroquímicas/métodos , Electrodos , Concentración de Iones de Hidrógeno , Límite de Detección , ProtonesRESUMEN
Molecular association between biocompatible dendritic polymers, dendrigraft poly-l-lysines (DGLs), and an anionic fluorescent probe, 8-anilino-1-naphthalenesulfonate (ANS-), was studied at the polarized water|1,2-dichloroethane (DCE) interface. The fluorescence intensity of ANS measured in aqueous solution was enhanced by the coexistence of DGLs over a wide pH range (2 < pH < 10), where ANS and DGL exist as a monoanionic form and a polycation, respectively. The voltammetric responses indicated that the positively charged DGLs were adsorbed at the water|DCE interface, whereas ANS- was transferred across the interface accompanied by the adsorption process. The interfacial behavior of the DGL-ANS associates was analyzed by potential-modulated fluorescence (PMF) spectroscopy. The PMF results demonstrated that the ion association between DGLs and ANS at the water|DCE interface is strongly affected by the applied potential and the dendritic generation of DGL. By applying appropriate potentials, the ANS anion was dissociated from its ion associate with DGLs at the interface and transferred into the organic phase, whereas DGLs remained in the aqueous phase. The Gibbs free energy of ion association (Δ GD···ANS) was estimated for the second-fourth generation DGLs (DGL-G2-G4) and the G4 polyamidoamine (PAMAM) dendrimer as a control. The highest stability of the DGL-G4-ANS associate manifested itself through Δ GD···ANS: DGL-G4-ANS (>G4 PAMAM dendrimer-ANS) > DGL-G3-ANS > DGL-G2-ANS. The results elucidated the efficient anion-binding ability of higher generation DGLs and its potential dependence at the liquid|liquid interface.