Enantioselectivity of some 1-(benzofuran-2-yl)-1-(1-H-imidazol-1-yl) alkanes as inhibitors of P450Arom

The low stereospecificity of the enantiomers of 1-[(benzofuran-2-yl)-4-chlorophenylmethyl]imidazole (6, R=H, R'=4'-Cl) and the corresponding 4-fluoro compound as inhibitors of aromatase (P450Arom) has been explored using 1-(5,7-dichlorobenzofuran-2-yl)-1-(1H-imidaz-1-yl)ethane (7, R1=R2=Cl, R=CH3), -propane (7, R1=R2=Cl, R=C2H5), and the corresponding 5,7-dibromo compounds resolved as their dibenzoyl-D (or -L) tartrates. Low enantioselectivity ratios of 4.8 (5,7-diCl) and 12.6 (5,7-diBr) were shown for the ethanes. The values for the corresponding propanes were 8.3 and 5.2, respectively, and for these compounds the stereoselectivity was reversed.     

Worldwide Residential Soil Regulatory Guidance Values for Chlorinated Ethanes

Surface soil contamination is often regulated using guidance values that specify the maximum amount of pollutant that can be present without prompting a regulatory response. In the United States, there are at least 89 value sets (and worldwide there are another 29) that provide guidance for at least one of the nine chlorinated ethanes. The most commonly regulated chlorinated ethane is 1,2-dichloroethane (108 values), and it is the third most commonly regulated synthetic organic surface soil contaminant. Pentachloroethane (17 values) is the least regulated chlorinated ethane. Overall, there are at least 690 guidance values for chlorinated ethanes. This analysis explores the origin, magnitude, and form of the variability of these values. Results indicate that the values span from 3.7 to 7.6 orders of magnitude and are distributed in patterns similar to log-normal random variables. Less than 20% of these values are similar to those of national regulatory agencies such as the U.S. EPA or the Canadian Council of Ministers of the Environment, but more than 60% of the values fall within the 95% confidence interval bounds of the uncertainty in U.S. EPA risk model calculations.     

Chlorinated Solvent Cometabolism by Butane-Grown Mixed Culture

A survey of aerobic cometabolism of chlorinated aliphatic hydrocarbons by a butane-grown mixed culture was performed. The transformation of 1,1-dichloroethylene (1,1-DCE) and cis-1,2-dichloroethylene (c-DCE) required O2 and was inhibited by butane and inactivated by acetylene, indicating that a monooxygenase enzyme was likely involved in the transformations. The initial transformation rates and the quantities of chlorinated aliphatic hydrocarbons transformed were inversely proportional to the chlorine contents within each group of chlorinated methanes, ethanes, and ethenes. Lower quantities of chloroform were transformed than chloromethane and dichloromethane, but chloroform transformation resulted in much higher cell inactivation. For the ethane group, chloroethane was most effectively transformed but caused significant cell inactivation. Di- or trichloroethanes that have all chlorines on one carbon were more effectively transformed and caused less cell inactivation than the isomers that have chlorine on both carbons. For chlorinated ethenes, 1,1-DCE was most rapidly transformed, whereas trans-1,2-dichloroethylene was not transformed. Vinyl chloride was transformed to the greatest extent, and very limited transformation of trichloroethylene was observed. The 1,1-DCE transformation caused greater cell inactivation than the transformation of the other chlorinated ethenes. Chloride release studies showed nearly complete oxidative dechlorination of chlorinated methanes and chloroethane, vinyl chloride and c-DCE (86% ～ 100%), and incomplete dechlorination of 1,1-dichloroethane, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2-trichloroethane, and 1,1-DCE (37% ～ 75%) was observed.     

Modeling Pd-Catalyzed Destruction of Chlorinated Ethenes in Groundwater

Groundwater contamination by chlorinated ethenes is a widespread environmental problem. Shortcomings in conventional remediation methods have motivated research into novel treatment technologies. A palladium/alumina catalyst in the presence of molecular hydrogen gas (referred to hereafter as the Pd/H2 system) has been demonstrated to destroy chlorinated ethenes in contaminated groundwater. This study presents a model for aqueous-phase destruction of chlorinated ethenes in contaminated groundwater using the Pd/H2 system that includes catalyst deactivation and regeneration. The model is validated using published data from laboratory column experiments from Stanford University. The model is then coupled with an analytical groundwater flow model to simulate application of in-well Pd/H2 reactors for in situ treatment of chlorinated ethene contaminated groundwater in a recirculating horizontal flow treatment Well (HFTW) system. Applying the model under realistic conditions results in approximately 130 days of HFTW system operation without significant catalyst deactivation. This suggests catalyst deactivation will not significantly affect system performance in a real remediation scenario. The model presented in this study, which simulates deactivation kinetics and regeneration of an in-well catalyst that is a component of a recirculating well system designed for in situ treatment of contaminated groundwater, represents an important step in transitioning the Pd/H2 technology to the field.     

Nonenzymatic and enzymatic hydrolysis of alkyl halides: a theoretical study of the SN2 reactions of acetate and hydroxide ions with alkyl chlorides

The SN2 displacements of chloride ion from CH3Cl, C2H5Cl, and C2H4Cl2 by acetate and hydroxide ions have been investigated, using ab initio molecular orbital theory at the HF/6-31+G(d), MP2/6-31+G(d), and MP4/6-31+G(d) levels of theory. The central barriers (calculated from the initial ion-molecule complex) of the reactions, the differences of the overall reaction energies, and the geometries of the transition states are compared. Essential stereochemical changes before and after the displacement reactions are described for selected cases. The gas phase reactions of hydroxide with CH3Cl, C2H5Cl, and C2H4Cl2 have no overall barrier, but there is a small overall barrier for the reactions of acetate with CH3Cl, C2H5Cl, and C2H4Cl2. A self-consistent reaction field solvation model was used to examine the SN2 reactions between methyl chloride and hydroxide ion and between 1,2-dichloroethane and acetate in solution. As expected, the reactions in polar solvent have a large barrier. However, the transition state structures determined by ab initio calculations change only slightly in the presence of a highly polar solvent as compared with the gas phase. We also calibrated the PM3 method for future study of an enzymatic SN2 displacement of halogen.     

担载双金属催化剂对Heck反应的作用

制备了0．5％Pd／C催化剂和含钯担载双金属催化剂3％Cu．0．5％Pd／C，3％Mo-0．5％Pd／C，3％Ni-0．5％Pd／C，3％Co-0．5％Pd／C．3％Mn-0．5％Pd／C，用XRD法和XPS法进行了表征。结果表明，室温下，以KBH4还原剂制备的含钯担载双金属催化剂，在碘苯与丙烯酸的Heck偶合反应中，催化活性高于Pd／C（0．5h的转化率高，完成反应所需时问少），显示出添加贱金属的协同效应。其中，3％Mo-0．5％Pd／C显示出最高的催化活性，在0．5h时的转化率（67．4％）和收率（52．6％）比0．5％Pd／C分别高54．5％和42．2％，完成反应的时问最短，表明钼的协同效应最高。     

Transformation of DDT and Its Metabolites by Various Abiotic Methods

This work looks at several new abiotic treatment methods for transformation of DDT in an aqueous solution. Various combinations of calcium peroxide (CaO2), zero-valent iron (Fe0), iron sulfide (FeS), and hydrogen peroxide (H2O2) were utilized to promote the abiotic transformation of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) in electrolyte, hydroquinone, and nonionic surfactant (Triton X-114) systems. Treatment with CaO2 resulted in 86% DDT mass reduction within 10?days of treatment with only traces of 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane (DDD) , 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE), and 1,1-dichloro-2,2-bis(4-chlorophenyl)ethylene (DDMU) being generated. Treatments with 1:1 mixtures of Fe0:CaO2 and FeS:CaO2 resulted in 86 and 85% DDT mass transformation, respectively, within 8?days. A mixture of 0.75?g?Fe0:0.1?g?CaO2 showed similar results with 79% DDT mass transformed within 8?days. A mixture of 0.75–0.1?g of Fe0:FeS resulted in 85 and 97% transformation in the total mass of DDT in an electrolyte solution and a hydroquinone solution, respectively. The treatment of DDT in aqueous solution by CaO2, in the presence of Triton X-114, resulted in the transformation of 97% of the total mass of DDT within 30?days, albeit, large amounts of DDE (402?μM) were generated.     

Cardiac chronotropic mechanisms of dimethyl sulphoxide: inhibition of acetylcholinesterase and antagonism of negative chronotropy by atropine

Phenobarbital, 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT), benzpyrene, 3-methylcholanthrene (3-MC) or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) were administered i.p. for 1 or 3 days to genetically "responsive" (C57BL/6J) and genetically "non-responsive" (DBA/2J) mice. 3-MC or benzpyrene stimulated aryl hydrocarbon hydroxylase (AHH) activity in C57BL/6J (B6) mice but not in DBA/2J (D2) mice. TCDD induced AHH activity in both B6 and D2 mice. Time-course studies showed that in the first 12 h after a single injection of 3-MC to B6 mice there was no shift in the reduced cytochrome P-450-CO complex absorption spectra from 450 to 448 nm, although AHH activity increased 4-5 times over (above) that of the control group. The relationship between induction of AHH activity by polycyclic hydrocarbons in B6 mice and the concomitant synthesis of cytochrome P-448 is discussed.     

High-Density Polyethylene Membrane Containing Fe0 as a Contaminant Barrier

To improve the performance of polymer-based containment barriers with respect to the breakthrough of chlorinated solvents, a high-density polyethylene (HDPE) membrane containing zero-valent iron (Fe0) nanoparticles was developed as a reactive barrier. The performance of the reactive membrane was evaluated by challenging it with carbon tetrachloride in a diaphragm cell apparatus. In a Fe0/HDPE system, reaction between carbon tetrachloride and Fe0 did not occur due to a lack of water in the polymer matrix. A glycerol-modified Fe0/HDPE membrane successfully increased the lag time before breakthrough by 13–16 fold compared to HDPE alone. Calculations estimate that only 2.5–3.0% of the Fe0 initially present in the membrane reacted before breakthrough of carbon tetrachloride. Extrapolations of these results to practical situations with larger membrane thicknesses and lower contaminant concentrations predict lag times on the order of years.     

Multiyear Temporal Changes in Chlorinated Solvent Concentrations at 23 Monitored Natural Attenuation Sites

Long-term (e.g., 5–15 years) groundwater concentration versus time records were compiled from 47 near-source zone monitoring wells at 23 chlorinated solvent sites (52 total records). Chlorinated volatile organic compound (CVOC) concentrations decreased significantly in most of the 52 temporal records, with a median reduction in concentration of 74%. A statistical method based on a Mann–Kendall analysis also showed that most sites had statistically significant decreasing concentration trends over time. Median point decay rate constants (kpoint) values were calculated for nine sites containing tetrachloroethene (PCE); 13 sites containing trichloroethene (TCE); two sites containing cis-1,2-dichloroethene (DCE); and six sites containing 1,1,1-trichloroethane (TCA). The TCA sites had the highest kpoint values (0.34/year) followed by PCE, DCE, and TCE (0.23/year, 0.16/year, and 0.11/year, respectively) (equal to decay half-lives of 2.0, 3.0, 4.3, and 6.1 years, respectively). If the median point decay rates from these sites are maintained over a 20 year period, the resulting reduction in concentration will be similar to the reported reduction in source zone concentrations achieved by active in situ source remediation technologies (typical project length: 1–2 years).     

Degradation of Lindane by Zero-Valent Iron Nanoparticles

Thus far, zero-valent iron has been studied mostly for the degradation of structurally simple one- and two-carbon halogenated organic contaminants such as chlorinated methanes, ethanes, and ethenes. In this research, laboratory synthesized particles of nanoscale iron were explored to degrade lindane, also known as γ-hexachlorocyclohexane, a formerly widely utilized pesticide and well-documented persistent organic pollutant. In general, lindane disappeared from aqueous solution within 24?h in the presence of nanoiron concentrations ranging from 0.015?to?0.39?g/L. By comparison, approximately 40% of the initial lindane dose remained in solution after 24?h in the presence of 0.53?g/L of larger microscale iron particles. However, the surface area normalized first-order rate constants were all within the same order of magnitude regardless of dose or iron type. A key reaction intermediate, γ-3,4,5,6-tetrachlorocyclohexene from dihaloelimination of lindane was identified and quantified. Trace levels of additional degradation products including benzene and biphenyl were detected but only in the high concentration experiments conducted in 50% ethanol. While up to 80% of the chlorine from the lindane molecules ended as chloride in water, only 38% of the expected chloride concentration was observed for the microscale iron experiment. This work together with previous published studies on the degradation of polychlorinated biphenyl, chlorinated benzenes, and phenols suggest that zero-valent iron nanoparticles can be effective in the treatment of more structurally complex and environmentally persistent organic pollutants such as lindane.     

Construction of bimetallic Pt-Pd/CeO2-ZrO2-La2O3 catalysts with different Pt/Pd ratios and its structure-activity correlations for three-way catalytic performance

A series of Pt-Pd bimetallic catalysts supported on CeO₂-ZrO₂-La₂O₃ mixed oxides were synthesized through the conventional impregnation method.Three-way catalytic performance evaluations along with detailed physio-chemical characterizations were carried out to establish possible structure-activity correlations.Results show that on the one hand,different Pt/Pd ratios can strongly affect the TWC behaviors of Pt-Pd/CZL catalysts by modulating the synergis...     

Investigations of hydrogen storage in palladium decorated graphene nanoplatelets

Carbon based nanomaterials are ideal media for hydrogen storage due to their highly porous structure, low density, and large surface area. The hydrogen uptake capacity of different carbon nanomaterials can be enhanced by spill over mechanism from a supported transition metal catalyst. In the present work graphene nanoplatelets (GNP) were prepared by thermal exfoliation method and decorated with palladium nanoparticles (Pd/GNP) by ethylene glycol reduction method. The high pressure hydrogen adsorption/desorption measurements were carried out for GNP and Pd/GNP using Sieverts apparatus in the temperature and pressure ranges of 25–100°C and 0.1–4 MPa, respectively. The hydrogen storage capacity of GNP and Pd/GNP were found to be 0.28 wt% and 1.21 wt% respectively at 25°C and 3.2 MPa pressure. Uniform dispersion of palladium nanoparticles over the surface of GNP enhances the hydrogen storage capacity of GNP by 70% due to spill over mechanism.     

Stepwise Chlorination-Chemical Vapor Transport Reactions for Bastnaesite Concentrate

Vapor phase extraction and mutual separation of rare earth (RE) elements from bastnaesite concentrate were investigated using stepwise chlorination-chemical vapor transport reactions mediated by vapor complexes LnAlnC13n 3(Ln = RE elements). The bastnaesite was heated to 800 K and chlorinated between 800- 1300 K with ,C C12 SiClr to remove CO2, SiF4 and high volatile chlorides. At the temperature of 1300 K for 6 h, the resulted RE chlorides were chemically transported and mutual separated with the vapor complexes while CaC12 and BaC12 were remained in the residues. Significantly different CVT characteristics were observed for gradually decreased and wave form temperature gradients.     

Transition metal doping effect and high catalytic activity of CeO2–TiO2 for chlorinated VOCs degradation

A series of transition metals (Fe, Co, Ni, Cu, Cr and Mn)-doped CeO₂–TiO₂ catalysts were prepared by the sol–gel method and applied for the catalytic removal of 1,2-dichloroethane (DCE) as a model for chlorinated VOCs (CVOCs). The various characterization methods including X-ray diffraction (XRD), N₂ adsorption–desorption, UV-Raman, NH₃ temperature-programmed desorption (NH₃-TPD) and H₂ temperature-programmed reduction (H₂-TPR) were utilized to investigate the physicochemical properties of the catalysts. The results show that doping Fe, Co, Ni or Mn can obviously promote the activity of CeO₂–TiO₂ mixed oxides for DCE degradation, which is related to their improved texture properties, acid sites (especially for strong acidity) and low-temperature reducibility. Particularly, CeTi–Fe doped with moderate Fe exhibits excellent activity for 1,2-dichloroethane (DCE) degradation, giving a T_90% value as low as 250 °C. More importantly, only trace chlorinated byproducts were produced during the low-temperature degradation of various CVOCs (dichloromethane (DCM), trichloroethylene (TCE) and chlorobenzene (CB)) over CeTi–Fe1/9 catalyst with high durability.     

Cis-Dichloro(diaminosuccinate diethyl ester)palladium (II) as Pd(II)/Pt(II) model compound for DNA-binding and antitumor properties: solution equilibria of their aqua-, hydroxo-, and/or chloro-species

Cis-Dichloro(diaminosuccinic acid)palladium(II), cis-[Pd(H2dasa)Cl2] (I), or cis-dichloro(diaminosuccinate diethyl ester)palladium(II), cis-[Pd(Et2dasa)Cl2] (II) reacts with two equivalents of AgClO4 to give insoluble Pd(dasa) or an aqueous solution of [Pd(Et2dasa) (H2O)2](ClO4)2, respectively. Three solutions of this salt were titrated with NaOH (I = NaClO4 (0.15M),37 degrees C), and 133 E(H+) data (3.5 < or = pH < or = 7) were treated by SUPERQUAD to fit log beta pqr of cis-aquahydroxo-(pqr = 10-1, -5.25(3)) and di-mu-hydroxo-species (20-2, -6.55(1)). At pH > 7 the ester hydrolysis prevents the calculation of log beta 10-2 for the cis-dihydroxo-complex. Another three solutions of such salt were titrated (I = 0.15M (NaClO4), 37 degrees C) with NaOH and NaCl simultaneously using two potentiometric systems (which measure H+ or Cl-). From 147 E(H+) and E(Cl-) data pairs and the above fixed log beta pqr, SUPERQUAD calculations yield log beta pqr for cis-chloro-aqua (pqr = 110, 3.65(1)), cis-chloro-hydroxo (11-1, -2.68 (4)), and cis-dichloro-species (120, 5.86(3)). Simulated and experimental titrations are in good agreement. Circular dichroism spectra of native DNA and drug:DNA complexes suggest that cis-Pd(H2dasa) and cis-Pd(Et2dasa) chelate moieties induce an opening and rotation of the stacked bases in the double helix. This finding is explained by the abundance of each one and of the total neutral and charged species of II in the tested CD solution.     

Metabolism of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)-ethane and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane in the mouse

The metabolites of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane (DDD) found in the urine of female Swiss mice are reported. The metabolites of DDT are DDD, 1-chloro-2,2-bis(p-chlorophenyl)ethene (DDMU), 1,1-dichloro-2-bis(p-chlorophenyl)ethene (DDE), 2,2-bis(p-chlorophenyl)acetic acid (DDA), 2-hydroxy-2,2-bis(p-chlorophenyl)acetic acid (alpha OH-DDA) and 2,2-bis(p-chlorophenyl)ethanol (DDOH), while DDD afforded DDMU, DDE, DDA, alpha OH-DDA and DDOH. The relative excreted levels of DDA and DDOH and the absence of 2,2-bis(p-chlorophenyl)acetaldehyde (DDCHO) are not consistent with the generally accepted pathway for DDA formation, which involves sequential metabolism of DDT and DDD via DDOH to afford DDA. The quantitative results are interpreted to mean that DDA is formed by hydroxylation at the chlorinated sp3-side chain carbon of DDD to give 2,2-bis(p-chlorophenyl)acetyl chloride (DDA-Cl), which in turn is hydrolyzed to DDA. The excretion of alpha OH-DDA from both DDT- and DDD-treated mice has never been previously observed. It is suggested that this metabolite arises from the initial epoxidation of DDMU, a metabolite of DDT and DDD, to yield 1,2-epoxy-1-chloro-2,2-bis(p-chlorophenyl)ethane (DDMU-epoxide). This chloroepoxide is then hydrolyzed and oxidized to produce the alpha OH-DDA.     

Transformation of Chlorinated Methanes by Nanoscale Iron Particles

This paper examines the potential of using laboratory-synthesized nanoscale iron particles to transform chlorinated methanes. The iron particles have diameters on the order of 1–100 nm (0.001–0.1 μm). Palladized iron particles were prepared by depositing palladium (0.05–1% Pd by weight) on the surface of iron. Batch experiments were conducted to compare reactions of chlorinated methanes with palladized nanoscale iron, nanoscale iron, and commercial grade iron particles (～10 μm). Rapid transformations of tetrachloromethane (CT) and trichloromethane (CF) were achieved with the palladized nanoscale iron particles. Typically 0.1 mM CT or CF was reduced below detection limits within 1 h. Methane and dichloromethane (DCM) were the major end products. Yields of methane and DCM from CT were 52% and 23%, respectively. Little degradation of DCM was observed within 72 h. With the nanoscale iron and commercial-grade iron particles, much slower reactions of chlorinated methanes were observed. Kinetic analyses indicated that the surface area-normalized rate coefficients kSA of the nanoscale iron and commercial grade iron particles were one to two orders of magnitude lower than those of the palladized nanoscale iron.     

Effects of Selected Good’s pH Buffers on Nitrate Reduction by Iron Powder

The effects of three selected Good’s pH buffers on the performance of an Fe0/nitrate/H2O system were evaluated. The Good’s pH buffer itself did not reduce nitrate directly. Nitrate reduction by iron powder at near-neutral pH was negligible in an unbuffered system, but it was greatly enhanced with the presence of the buffer. A significant amount of aqueous Fe2+ (or Fe3+) was released after adding the Good’s pH buffer into the Fe0/H2O system with or without nitrate. In general, the pH of the buffered solution increased from the initial pH ( = ～ 4.6–5.3, depending on buffer’s pKa) to near-neutral pH. After the initial pH hiking, the pH in the system was more or less stable for a period of time ( ～ 5–10?h, usually concurrent with a fairly stable aqueous Fe2+). The pH then drifted to ～ 7.1 to 8.6, depending on the buffer’s initial concentration, the buffer’s pKa, and the consumption of Fe2+ concurrent with nitrate reduction. While a common assumption made by researchers is that Good’s pH buffers do not directly participate in reaction processes involved in contaminant remediation, this study shows that as side effects, the Good’s pH buffer may react with iron powder.     

银电解过程中钯的回收

针对金银冶金过程中铂钯的分布特点,提出了采用黄药富集分离、氯钯酸铵—二氯二氨络亚钯联合沉淀、水合肼还原的方法从银电解阳极泥中回收钯的新工艺。结果表明,所得海绵钯纯度大于99.95%,直收率大于97%。该工艺具有选择性分离钯效果好、过程无需赶硝、产品质量稳定等优点。