Rapid synthesis of the low thermal expansion phase of Al<Subscript>2</Subscript>Mo<Subscript>3</Subscript>O<Subscript>12</Subscript> via a sol–gel method using polyvinyl alcohol

Aluminum molybdate was successfully synthesized using a simplified PVA assisted sol–gel method resulting in highly crystalline, monophasic (monoclinic P2₁/a) samples. These materials could readily be obtained at temperatures of 600 and 700 °C after calcining for as little as 15–20 min. Scanning electron microscopy and X-ray powder diffraction indicated that even the sample calcined at 600 °C for 20 min was free of impurities and composed of submicron sized particles (~300 nm). Transmission electron microscopy was used to confirm the monophasic character and submicron dimensions of the as-prepared powders. In addition to producing high quality samples, it was also observed that the metal to PVA ratio used during this simplified synthesis, could be used as a control parameter for tailoring the particle sizes of the final product.     

The effect of additives on the speed of the crystallization front of xylitol with various degrees of supercooling

Some liquids can be kept in a supercooled or supersaturated metastable state for substantially long periods. Such liquids can be applied as long-term heat storage where the latent heat can be released when needed. As xylitol possesses a relatively high value of latent heat and as it can be easily supercooled, it has promising properties for this application. However, the speed of the crystallization of xylitol is low, leading to a low release rate of latent heat.Several additives have been experimentally tested for the purpose of accelerating the crystallization speed. The effect of the additives on the latent heat, on the melting temperatures, and on the long-term durability of the supercooled state was also measured.The highest speeds of the crystallization front, at a temperature of 22 °C, were achieved with methanol as an additive leading to speeds 33 times higher in vertical experiments and in 170 times higher in horizontal ones than with pure xylitol. The improved speed of the crystallization front is mostly caused by the methanol flow currents generated as a result of the separation of methanol during crystallization, and to a lesser extent, as a result of the increase in the speed of the growth of the crystals.     

Sorption of metal ions to untreated,alkali-treated and peroxide-bleached TMP

Knowledge about how different metal ions are bound to pulp fibers is very important for optimal metal management in pulping processes. A column chromatographic method was used to assess the differences in affinity of 14 metal ions to untreated, alkali-treated and peroxide-bleached thermomechanical pulp (TMP). A method of competition between cations in the column chromatographic experiments was used in the sorption experiments, with an excess of each metal ion compared to the total capacity of the pulp studied. The method is very sensitive and even small differences in affinities can be detected. By combining the results from sorption experiments with four different metal ion mixtures the following order of affinity was obtained: Pb²⁺ ≫ Cu²⁺ ≫ Cd²⁺ > Zn²⁺ > Ni²⁺ > Ba²⁺ > Ca²⁺ > Mn²⁺ > Sr²⁺ > Mg²⁺ ≫ Rb⁺ ≈ K⁺ > Na⁺ > Li⁺. All three types of pulps showed the same affinity order. Lead and copper ions were clearly most strongly bound to the pulp fibers. Within the alkali and alkaline earth metal groups the differences in affinity were quite small. The sorption of metal ions to pulp fibers takes place mainly by complexation, where the divalent metal ions are coordinated to functional groups (acid groups) in the fiber phase. Protonation constants and concentrations of acid groups were determined by potentiometric titration. A model with two carboxyl groups and two phenolic hydroxyl groups satisfied best the experimental data. By treatment with alkali and peroxide new acid groups were created and the total binding capacity of hydrogen ions increased from 137 μeq/g for untreated pulp to 187 and 228 μeq/g for alkali-treated and peroxide-treated pulp, respectively.     

Total synthesis of nor-1,6-germacradien-5-ols

The first total synthesis of (+/-)-nor-1,6-germacradien-5-ols is described. The synthetic route involves the RCM methodology for the ring formation and a selective 1,2 addition of MeLi to cyclodecenone. By altering the order of the last synthetic steps, TBSO-protected (+/-)-(1Z,6E)-nor-1,6-germacradien-5-ols (+/-)-(5S*,8R*)-16 and -(+/-)-(5S*,8S*)-16 were obtained. The synthetic strategy via cyclodecenone offers the possibility of preparing different analogues of the title compounds through addition of other nucleophiles. Moreover, nor-germacrene D could be accessed from the target molecule by methylenation of its carbonyl moiety. (+/-)-nor-1,6-Germacradien-5-ol [(+/-)-(1E,5S*,6E,8S*)-2] was synthesized in eight steps from isovaleric acid. The 10-membered ring was formed by RCM, and the tertiary alcohol moiety was introduced in the last step via a highly diastereoselective addition of MeLi to (+/-)-(1E,6E)-1,6-cyclodecen-5-one (+/-)-E,E-5. Addition of MeLi to cyclodecenone (+/-)-Z,E-5 also occurred with complete selectivity to provide (+/-)-(1Z,5S*,6E,8S*)-2. A slightly different synthetic pathway was also explored, in which the order of the final synthetic steps was switched: the enone formation and the addition of MeLi were conducted prior to the cyclization. When the hydroxy group was protected as a TBS ether, the newly formed olefin had exclusively Z configuration. Thus, TBSO-protected (+/-)-(1Z,6E)-nor-1,6-germacradien-5-ols (+/-)-16 were obtained as a 1:1 (5S*,8S*)/(5R*,8S*) mixture. The NMR spectra of these two diastereomers confirmed the relative stereochemistry of natural (-)-1,6-germacradien-5-ol (1) at C5 and C8.     

“First‐Principles” kinetic monte carlo simulations revisited: CO oxidation over RuO2(110)

First principles‐based kinetic Monte Carlo (kMC) simulations are performed for the CO oxidation on RuO₂(110) under steady‐state reaction conditions. The simulations include a set of elementary reaction steps with activation energies taken from three different ab initio density functional theory studies. Critical comparison of the simulation results reveals that already small variations in the activation energies lead to distinctly different reaction scenarios on the surface, even to the point where the dominating elementary reaction step is substituted by another one. For a critical assessment of the chosen energy parameters, it is not sufficient to compare kMC simulations only to experimental turnover frequency (TOF) as a function of the reactant feed ratio. More appropriate benchmarks for kMC simulations are the actual distribution of reactants on the catalyst's surface during steady‐state reaction, as determined by in situ infrared spectroscopy and in situ scanning tunneling microscopy, and the temperature dependence of TOF in the from of Arrhenius plots. © 2012 Wiley Periodicals, Inc.     

Influence of anionic additive on Hg(2+) interference on Ag(+)-ISEs based on [2.2.2]p,p,p-cyclophane as neutral carrier

The influence of the anionic additive on the Hg²⁺ interference on Ag⁺-ion-selective electrodes (Ag⁺-ISEs) based on [2.2.2]p,p,p-cyclophane as π-coordinating neutral carrier was studied by potentiometric measurements. The weakly coordinating carborane anion (7,8,9,10,11,12-hexabromocarborane, CB₁₁H₆Br₆⁻) was compared with the commonly used tetrakis(4-chlorophenyl borate) (TpClPB⁻) as the anionic additive in plasticized PVC membrane-based Ag⁺-ISEs. The Hg²⁺ interference was reduced by six orders of magnitude when replacing TpClPB⁻ with CB₁₁H₆Br₆⁻ as the anionic additive, resulting in determined by the matched potential method (MPM). This indicates that weakly coordinating carboranes may be particularly useful as anionic additives in ISEs for soft cations.     

Synthesis and ROMP activity of aminophenol-substituted tungsten(VI) and molybdenum(VI) complexes

Tungsten(VI) and molybdenum(VI) complexes [MO(L¹)Cl₂] and [M(X)(L²)Cl₃] (X = O, NPh) with tridentate aminobis(phenolate) ligand L¹ = methylamino-N,N-bis(2-methylene-4,6-dimethylphenolate) and bidentate aminophenolate ligand L² = 2,4-di-tert-butyl-6-((dimethylamino)methyl)phenolate) were prepared and characterised. These complexes are principally stable in open atmosphere under ambient conditions. When activated with Et₂AlCl, they exhibited high activity in ring-opening metathesis polymerisation (ROMP) of 2-norbornene (NBE) and its derivatives. Especially complexes [M(NPh)(L²)Cl₃], which are easily available from corresponding metal oxides MO₃ by a simple three-step synthesis, were found very efficient ROMP catalysts for NBE (M = Mo, W) and 2-norbornen-5-yl acetate (M = Mo).     

Comparison of triple quadrupole,hybrid linear ion trap triple quadrupole,time‐of‐flight and LTQ‐Orbitrap mass spectrometers in drug discovery phase metabolite screening and identification in vitro – amitriptyline and verapamil as model compounds

Liquid chromatography in combination with mass spectrometry (LC/MS) is a superior analytical technique for metabolite profiling and identification studies performed in drug discovery and development laboratories. In the early phase of drug discovery the analytical approach should be both time‐ and cost‐effective, thus providing as much data as possible with only one visit to the laboratory, without the need for further experiments. Recent developments in mass spectrometers have created a situation where many different mass spectrometers are available for the task, each with their specific strengths and drawbacks. We compared the metabolite screening properties of four main types of mass spectrometers used in analytical laboratories, considering both the ability to detect the metabolites and provide structural information, as well as the issues related to time consumption in laboratory and thereafter in data processing. Human liver microsomal incubations with amitriptyline and verapamil were used as test samples, and early‐phase ‘one lab visit only’ approaches were used with all instruments. In total, 28 amitriptyline and 69 verapamil metabolites were found and tentatively identified. Time‐of‐flight mass spectrometry (TOFMS) was the only approach detecting all of them, shown to be the most suitable instrument for elucidating as comprehensive metabolite profile as possible leading also to lowest overall time consumption together with the LTQ‐Orbitrap approach. The latter however suffered from lower detection sensitivity and false negatives, and due to slow data acquisition rate required slower chromatography. Approaches with triple quadrupole mass spectrometry (QqQ) and hybrid linear ion trap triple quadrupole mass spectrometry (Q‐Trap) provided the highest amount of fragment ion data for structural elucidation, but, in addition to being unable to produce very high‐important accurate mass data, they suffered from many false negatives, and especially with the QqQ, from very high overall time consumption. Copyright © 2010 John Wiley & Sons, Ltd.     

Dynamic response of chlorine atoms on a RuO(2)(110) model catalyst surface

The dynamic behavior of surface accommodated chlorine atoms on RuO(2)(110) was studied by a variety of experimental methods including high resolution core level shift, thermal desorption-, and in situ infrared spectroscopy as well as in situ surface X-ray diffraction in combination with state-of-the-art density functional theory calculations. On the chlorinated RuO(2)(110) surface the undercoordinated oxygen atoms have been selectively replaced by chlorine. These strongly bound surface chlorine atoms shift from bridging to on-top sites when the sample is annealed in oxygen, while the reverse shift of Cl from on-top into bridge positions is observed during CO exposure; the vacant bridge position is then occupied by either chlorine or CO. For the CO oxidation reaction over chlorinated RuO(2)(110), the reactant induced site switching of chlorine causes a site-blocking of the catalytically active one-fold coordinatively unsaturated (1f-cus) Ru sites. This site blocking reduces the number of active sites and, even more important, on-top Cl blocks the free migration of the adsorbed reactants along the one-dimensional 1f-cus Ru rows, thus leading to a loss of catalytic activity.     

Electrochemical Behaviour of Poly(benzopyrene) Films Doped with Eriochrome Black T as a Pb2+‐Sensitive Sensors

Poly(benzopyrene) films were electrosynthesized on glassy carbon disk electrodes from benzo(a)pyrene by cyclic voltammetry in the presence of eriochrome black T, which forms strong complexes with lead ions. In consequence, by conditioning the films in high concentration of lead (0.1 mol dm^?3 Pb(NO₃)₂) potentiometric sensitivity to lead ions down to 10^?5 mol dm^?3 Pb²⁺ was induced, and a novel type of lead‐sensitive electrode was obtained. The electrode is characterized by high stability of the potential readouts, good reproducibility of the calibration curves as well as a minor hysteresis effects. The performance of our lead‐sensitive electrode was favourable compared to PEDOT and PPy‐based electrodes doped with eriochrome black T. We conclude that poly(benzopyrene) doped with eriochrome black T is a new electroactive material that may be applied in sensor technology.