Double bond isomerization of 5-vinylbicyclo[2.2.1]hept-2-ene to 5-ethylidenebicyclo[2.2.1]hept-2-ene over alkaline earth oxides

All the alkaline earth oxides exhibit activities for double, bond isomerization of 5-vinylbicyclo[2.2.1]hept-2-ene (VBH) to 5-ethylidenebicyclo[2.2.1]hept-2-ene (EBH) at a reaction temperature of 273 K. The order of the activity on the basis of unit weight of catalyst was CaO>MgO>SrO>BaO when compared under optimum pretreatment conditions. The E/Z ratio in the products is determined by the reaction temperature regardless of the type of catalyst; the ratios were 82/18 and 88/12 for the reaction temperatures of 323 and 273 K, respectively.     

Partial Hydrolysis of Cyanide Coordination Polymers Induced by a Pillar Ligand with Optimized Electrochemical Kinetics for Rechargeable Alkaline Batteries

Coordination polymers are promising cathode materials for rechargeable alkaline batteries. Therefore, the precise modulation of these cathodes by chemical structure and in-depth structure transform study is necessary. Here, two model coordination polymer battery cathodes were designed to demonstrate the dynamic structure–performance relationship. We studied the electrochemical performance of two kinds of nickel-based coordination polymer, comprising a planar 2D cyanide-bridged network and a 3D cyanide-bridged network pillared by pyrazine molecules. The 2D coordination polymer showed serious voltage degradation with poor rate capability, whereas the 3D coordination polymer exhibited stable voltage output coupled with high rate at various current densities. The investigation revealed the underlining relationship of plateau voltage degradation and hydrolysis process of electrodes. It was revealed that the pyrazine pillar molecules in the 3D coordination polymer could suppress the hydrolysis and lead to the in situ formation of partially hydrolyzed structure with excellent electrochemical kinetics; this exhibited obvious smaller peak separation (27 mV compared with 149 mV) and hence an almost twofold increase in capacity retention (31.9 to 50.0 %) and energy density retention (18.2 to 35.9 %) at 10 A g⁻¹.     

Uranium Dissolution in Hyperalkaline TMA-OH Solutions: Preliminary Results

Leaching experiments were performed with depleted UO₂ powders in tetramethylammonium solutions (TMA-OH) at pH 13.5 and 12.5, and at different UO₂ surface area to volume of solution (SA/V) ratio's to determine the solubility and the dissolution kinetics of UO₂ at high pH in absence of cations dominating cementitious waters (Ca,Na, K).The solubility of UO₂ increased from pH 12.5 to 13.5 and by increasing the SA/V ratio up to 100 m^-1. However, no known U secondary-phases were predicted by geochemical calculations to control the measured U-concentrations. A two-step dissolution process was put forward: 1-a fast initial rate, surface controlled and hydroxo promoted and 2-a sorption process at low SA/V ratio or a continuous residual dissolution process at high SA/V ratio.     

Minireview: Advances in Germanium Isotope Analysis by Multiple Collector–Inductively Coupled Plasma–Mass Spectrometry

The advent of multiple collector–inductively coupled plasma–mass spectrometry (MC-ICP-MS) has made the high-precision determination of Ge isotopes possible, which leads to the widespread application of Ge isotopes in earth, ocean, and cosmochemistry fields. This paper reviews the history of Ge isotope analysis, chemical dissolution and purification, and mass spectrometry measurements. Concentrated HNO₃ is sufficient to dissolve nearly all types of samples and HF is also involved for Si-rich samples. Low-temperature ashing prior to dissolution is an alternative way to preconcentrate Ge in organic-rich samples. For different matrices, Ge isotopes can be determined by MC-ICP-MS coupled with a traditional nebulizer system or hydride generation system after two-step separation, one step cation/anion-exchange separation, or Mg/Fe co-precipitation protocols. Ion-exchange column methods are suitable for samples with elevated matrix and Ge content such as sulfides, iron oxides, silicate rocks, and coals, whereas Mg or Fe coprecipitation methods are particularly suitable for all kinds of water. Hydride generation systems are improved over traditional nebulizer system due to the smaller sample quantity and fewer matrix-related interferences. Sample-standard bracketing, double spike, and external Ga isotope normalization are used to mass bias correction and yield consistent results. Analytical methods involving Ge-poor samples and Ge isotope analyses based on different Ge species or specific Ge compound in natural environment will be important prospects in the further study. For further applications of Ge isotopes in mineral deposits such as sulfide and iron oxide deposits, sulfides, and iron oxides reference materials should be developed in the future.     

Structures of oxaliplatin‐oligonucleotide adducts from DNA

Oxaliplatin, [(1R,2R)‐cyclohexane‐1,2‐diamine](ethanedioato‐O,O')platinum(II) shows a great efficiency against colorectal cancer. Although the mode of action of oxaliplatin is not yet understood, it is commonly accepted that binding of oxaliplatin to DNA prevents DNA synthesis and alters protein to DNA binding. In order to elucidate the modified DNA–protein interaction and thus to understand the mechanisms leading to cellular misinterpretation of DNA information and apoptosis, we have identified the preferential binding sites and the dynamics of the oxaliplatin‐DNA intrastrand and interstrand adducts at the oligomer level using high‐performance liquid chromatography/electrospray ionization‐tandem mass spectrometry (HPLC/ESI‐MS/MS) and HPLC/inductively coupled plasma‐MS for quantitative studies. We used a combination of benzonase, alkaline phosphatase and Nuclease S1 for digestion. This digestion procedure allows the study of platinated oligomeric nucleotides and more complex interstrand adducts. The digestion products were mostly chromatographically separated and characterized using HPLC/ESI‐ion trap MS/MS experiments. We could show that the adducts to guanine and adenine are quite dynamic; that is, the ratios are changing for several days. In addition, the resulting adducts provide evidence for the action of the digesting enzymes and indicate that the adduct spectrum at the oligomeric level is different to that at the commonly studies dinucleotide level. Copyright © 2012 John Wiley & Sons, Ltd.     

Substituted Quinolinones. Part 19. New and Unexpected Results from Oxidation of 3-Acetyl-1-Alkyl- 4-Hydroxyquinolin-2(1H)-Ones Using Selenium Dioxide

Abstract

Oxidation of 3-acetyl-1-alkyl-4-hydroxyquinolin-2(1H)-ones using selenium dioxide under Riley conditions was described. The oxidation reaction produced a mixture of 2 unexpected α-keto acid and its dehydrated dimer derivatives. The oxidation reaction was studied under different reaction conditions in order to maximize the yields and optimize reaction conditions. Also, 1-alkyl-4-hydroxy-3-(2-nitroacetyl)quinolin-2(1H)-one and/or 3-acetyl-1-alkyl-4-diflouro-boryloxyquinolin-2(1H)-one derivatives were subjected to the same oxidation reaction giving rise improved reaction yields and selectivity in case of the boron-complex. Alkaline degradation of the dehydrated dimers led to formation of the 4-hydroxy-2-oxoquinoline-3-carboxylic acids while under the same conditions the α-keto acids underwent deoxalylation.

[Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the following free supplemental files: Additional figures].     

Highly alkaline stable anion exchange membranes from nonplanar polybenzimidazole with steric hindrance backbone

The anion exchange membranes (AEMs) with both high ionic conductivity and alkali stability are always the research focus of the AEM fuel cells. Here, a novel nonplanar polymer for AEMs manufacture, mPBI‐TP‐x‐R, with excellent hydroxide stability and satisfactory processability is reported for the first time. The serial mPBI‐TP‐x resins with steric hindrance were prepared by copolymerization among 3,3′,4,4′‐tetraaminobiphenyl, isophthalic acid and tetraphenyl‐terephthalic acid (TP) in different ratios under microwave condensation. The copolymers mPBI‐TP‐x were quaternized at N1/N3‐sites of benzimidazole unit in backbone with alkyl groups (R?CH₃, C₂H₅, n‐C₃H₇, or n‐C₄H₉) to prepare soluble ionomers, and the corresponding membranes in hydroxyl ion form were prepared by a solution casting method and subsequent ion‐exchange process. The chemical structure of all membranes was characterized using FTIR and ¹H NMR spectroscopy. The properties of ion exchange capacity, water uptake, swelling ratio, tensile strength, ionic conductivity, and alkaline stability were measured. Among the prepared membranes, the mPBI‐TP‐15%‐(n‐Bu) exhibited the excellent alkaline stability (only degradation ca. 5% under 1M NaOH aqueous solution at 60 °C for 800 h) and satisfactory OH^? conductivity (46.66 mS/cm at 80 °C). The current research provides a useful exploration to commercial application of alkaline fuel cell. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 1087–1096     

自动石墨消解–电感耦合等离子体质谱法同时测定左氧氟沙星胶囊中7种金属元素

建立自动石墨消解-电感耦合等离子体质谱法(ICP-MS)同时测定左氧氟沙星胶囊中铅、铬、砷、镉、锡、铝、铁7种金属元素含量的方法。以HNO3-H2O2()体积比为1∶1为消解体系,采用自动石墨消解法消解左氧氟沙星胶囊样品,消解液除酸后,用5%硝酸溶液定容至50 mL,采用电感耦合等离子体质谱法对消解液进行测定,以内标法定量。铅、铬、砷、镉、锡、铝、铁的质量浓度在0.05~20.0μg/mL范围内与质谱响应值成良好的线性关系,相关系数均大于0.998,方法检出限为0.119~1.323μg/kg。样品加标回收率为91.2%~105.5%,测定结果的相对标准偏差为1.67%~3.46%(n=6)。该方法样品前处理简单,检出限低,测定结果准确,适用于左氧氟沙星胶囊等沙星类抗生素中多种金属元素残留的测定。     

Reversible M−M Bonding by Alkaline Earth Metals (Mg,Ca, Sr,Ba) in Graphite Intercalation Compounds

The alkaline earth metals (M=Mg, Ca, Sr, and Ba) exhibit a +2 oxidation state in nearly all known stable compounds, but M^I dimeric complexes with M−M bonding, [M₂(en)₂]²⁺, (en=ethylenediamine) of all these metals can be stabilized within the galleries of donor-type graphite intercalation compounds (GICs). These metals can also form GICs with more conventional metal (II) ion complexes, [M(en)₂]²⁺. Here, the facile interconversion between dimeric-M^I and monomeric-M^II intercalates upon the addition/removal of en are reported. Thermogravimetry, powder X-ray diffraction, and pair distribution function analysis of total scattering data support the presence of either [M₂(en)₂]²⁺ or [M(en)₂]²⁺ guests. This phase conversion requires coupling graphene and metal redox centers, with associated reversible M−M bond formation within graphene galleries. This chemistry allows the facile isolation of unusual oxidation states, reveals M⁰→M²⁺ reaction pathways, and present new opportunities in the design of hybrid conversion/intercalation materials for applications such as charge storage.     

Exploratory Analysis for Elemental Characterization of Biomass Residues From Biodiesel Production by Inductively Coupled Plasma Optical Emission Spectrometry

Edible and non-edible seeds with high oil content are used as the main raw material for biodiesel production. The residual biomass (press cake or oil cake) can be used as animal feed, to aggregate value to the biodiesel production cycle. In this work, a microwave-assisted-digestion procedure for elementary determination by inductively coupled plasma optical emission spectrometry (ICP OES) using dilute nitric acid was developed. Inter-laboratorial reference material was used to check the accuracy. A full factorial design in addition to exploratory analysis through principal component analysis (PCA) and hierarchical cluster analysis (HCA) were used to classify the samples: press cakes from castor (Ricinus communis), jatropha (Jatropha curcas), radish (Raphanus sativus), sunflower (Heliantus annus), and coffee (Coffe arabica), according to their similarities.