Application of a geometric model to the hydrogenation of Ti2Ni and Ti4Fe2O

A geometric model has been used to predict which interstices should be preferred by hydrogen (deuterium) atoms in the hydrides of Ti₂Ni and Ti₄Fe₂O. Crystallographically, both of these intermetallic compounds are closely related to the η carbide structure, but the model predicts significant differences in their preferred hydrogen sites. The most important tetrahedral sites in Ti₂NiH should be those coordinated by four nickel atoms, while in Ti₄Fe₂OH_2.25 the analogous sites coordinated by four iron atoms should be unoccupied. In contrast with Zr₃V₃O, another oxygen-stabilized compound with the η carbide structure, the most important type of tetrahedral interstice in Ti₄Fe₂O should be the one sharing a face with an octahedral interstice containing an oxygen atom. All these predictions of the model are in agreement with published experimental determinations of site occupation.     

Physicochemical Nature of Perfluoroalkyl Compounds Induced by Fluorine

Perfluoroalkyl (R_f) compounds have unique characters represented by a significantly high hydrophobic property, which often makes us consider that R_f groups should be interacted with each other via the ‘hydrophobic interaction’ as found for a normal hydrocarbon. Due to a similar intuitive and simplistic speculation, the R_f‐specific material properties have long been enveloped in darkness for comprehensive understanding, which should lucidly be discussed within a framework of physical chemistry. Here, we show studies on the stratified dipole arrays (SDA) theory, which readily explains the R_f‐specific material characters in a comprehensive manner based on only a few fundamental physical parameters of fluorine. The SDA theory encompasses some conventional theories that account for only a part of material properties. In addition, we show that the concept of vibrational spectroscopy of R_f compounds should also be revised, since the mass of fluorine is larger than that of carbon, which is opposite to the hydrocarbon case. In this manner, chemistry of R_f compounds needs another fully revised concept, which cannot be replaced by an extended concept of normal hydrocarbon compounds.     

Nucleophilic cosubstitution of poly(dichlorophosphazene) with alkyl ether and amino acid ester

The nucleophilic substitution reaction of poly(dichlorophosphazene) with sodium 2‐methoxyethoxide and glycine ethyl ester has been studied in detail. Polymers prepared with different methods have been characterized by ¹H NMR, and the results reveal that the addition sequence of the two nucleophilic reagents is an important factor in determining the structure of the resultant polymer. If alkyl ether is added first, the subsequently introduced amino acid ester not only reacts with residual P? Cl but also attacks the alkyl ether side units present by replacing either the whole group or just ? OCH₃. As a result, a new kind of side group (? OCH₂CH₂NHCH₂COOC₂H₅) can be detected in the macromolecule. To obtain polymers with desired compositions {poly[(methoxyethoxy)_x(ethylglycino)_yphosphazene]}, the amino acid ester should be introduced initially to react with poly(dichlorophosphazene), and it should be followed by the alkyl ether. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2417–2425, 2005     

Modified statistical theory of energy transfer in ion-molecule collisions

The modified statistical theory developed previously for potentials appropriate to interactions in neutral-neutral collisions, is now extended to more strongly attractive potentials involved in ion-neutral collisions. The model system is the collisional deactivation of C₅H₉⁺ by a variety of both polar and non-polar neutral molecules. A 12 - 6 - 4 potential is used for ion interaction with non-polar neutrals, and a 12 - 6 - 4 - 2 potential, as modified by Su and Bowers to take into account the rotational energy of the neutral, for interaction with polar neutrals. Calculated is (ΔE), the average energy lost by the ion in a collision, and compared with experiment. For C₅H₉⁺-CH₄ collisions, the calculated (ΔE) agrees with experiment within 5%. Predictions of the theory, namely that (ΔE) should increase with excitation energy and should decrease with the size of the excited reactant, are found to be in fair agreement with the somewhat ambiguous experimental evidence.     

Structural effects in heteroatom systems. II. The calculated influence of steric effects on polymerization–depolymerization equilibria in the siloxane and oxymethylene series. Comparisons with the phosphazene system.

The relative stabilities of symmetrically substituted polysiloxanes and polyoxymethylenes are compared in terms of the side-group steric overlap parameters, by means of a semiempirical method described previously. The results provide a qualitative estimate of the relative thermodynamic ease of polymerization of cyclic siloxanes or monomeric methylene oxides or, conversely, of the relative resistance to depolymerization of the polymers. These calculated values are compared with those reported previously for phosphazenes. In general, for polymers of the type, [R₂Si? O]_n, [R₂C? O]_n, and [R₂P?N]_n, if the side group, R, is small (H, halogen or methyl) the inherent steric and bonding characteristics of the chain should cause the polymer stabilities to decrease in the order phosphazenes ≈ siloxanes ? oxymethylenes. If, however, bulkier side groups are present, the order of decreasing stability to depolymerization should be siloxanes > phosphazenes ? oxymethylenes. In all cases, the depolymerization tendency should increase markedly as the side group overlap parameters increase, and polyoxymethylenes should be the most sensitive to such changes. The calculated results are compared with the limited experimental evidence at present available.     

Semiconductor nanocrystals possessing broadly size‐ and facet‐dependent optical properties

Cu₂O cubes, octahedra, and rhombic dodecahedra have been shown to exhibit continuous light absorption and emission band shifts with increasing particle sizes from 10 nm to sub‐microcrystals. They also possess clear facet‐dependent optical properties. Ag₃PO₄, Ag₂O, SrTiO₃, and CeO₂ crystals show similar optical size and facet effects. Thus, spectral shifts over a broad size range far beyond the quantum‐size regime should be generally observable in many semiconductor materials. Facet‐dependent optical properties of a semiconductor can be understood to arise from the presence of an ultrathin surface layer with subtle bond and orbital level variations for different crystal faces. Although these optical features seem unexpected, they should be the general behaviors of semiconductor crystals. As more examples of these optical effects are available, we will find that these intrinsic properties of semiconductors have been ignored in the past. Furthermore, if valence and conduction band positions are broadly tunable by particle size, the knowledge should have tremendous impacts on the applications of semiconductors, where band energies are important to efficient interfacial charge transfer.     

Chemical consequences of electron scavenging by SF6 in radiolysis experiments

Contrary to the usual assumption that it is unreactive, SF₆^? formed by electron attachment is found to undergo rapid bimolecular reactions with molecules (HX) possessing acidic hydrogen, including HCl, HBr, HCO₂H, CH₃CO₂H, H₂S, and HCN. It is clear for many systems that meaningful mechanistic inferences about radiolytic processes occurring in the presence of SF₆ should consider a wide variety of non-scavenging reactions. Appropriate caution should be exercised in any experiment in which SF₆ is used to scavenge and detect low energy electrons. The reaction sequences observed are interesting in that they provide convenient bimolecular pathways for the formation of a variety of anionic dimers of the type XHY^?.     

Influence of Nox on soot combustion with supported molten salt catalysts

Diesel soot is combusted simultaneously by two reactions: combustion with NO₂ and combustion with O₂ with the aid of a molten salt catalyst. Both reaction pathways should always be considered to avoid misinterpretation of experimental data.     

A particle growth theory for heterogeneous Ziegler polymerization

Samples of “as produced” polypropylene particles at progressively higher yield levels (grams polymer/gram catalyst) were sliced and examined by electron microscopy. In the polymerization of propylene with the TiCl₃–(C₂H₅)₂AlCl catalyst system the catalyst breaks up immediately into basic 100–1000 Å particles. As the yield increases, the catalyst particles gradually disappear and finally become completely dispersed in the polymer particle. These results are compatible with a theory which views the catalyst as a porous crystal containing a single species of active sites uniformly distributed. As polymerization progresses, all sites should eventually initiate a polymer chain whose length should be inversely proportional to the depth of the site below the surface of the particle. Two apparently equivalent statistical models were developed on the basis of this concept. Both models predict a slow increase in the X?_w/X?_n ration (Q) with increasing molecular weight, after an initial rapid increase. The most useful of these models states that Q is equal to the sum of X?_w terms of the simple harmonic series, and that a complete spectrum of x-mers should be present in the product. This agrees satisfactorily with analytically determined values.     

Characterization of the active phase of NiMo/Al2O3 hydrodesulfurization catalysts

The active phase of the NiMo/Al₂O₃ catalyst for hydrodesulfurization reactions has been investigated in this work. Special attention has been focused on the effect of the order of metal impregnation on the formation of the active phase in the reaction. The Mo and Ni oxides and their sulfides on the alumina were investigated by XPS and DRS analyses. The Ni-Mo oxides or precursor of the active phase which are chemically bonded between Mo and Ni were also confirmed from the binding energy shifts of the XPS peaks. The amount of Ni-Mo oxides was determined after the formation of metal oxides during calcination. The Ni-Mo sulfide (active phase) was then induced through sulfidation. It was important that Mo should be located at the tetrahedral sites on the alumina with a high Mo dispersion. These results indicated that there are two important factors in preparing highly efficient Ni-Mo catalysts; one is that Mo should be located at the tetrahedral coordination on Al₂O₃ in high dispersion (Mo/Al₂O₃) and the other is that the Ni species should be supported on MoAl₂O₄ to form Ni-Mo oxides which change into the Ni-Mo sulfide active sites by sulfidation.     

Solvent-free mechanochemical synthesis of diacylfuroxans

Acetophenones with a variety of substituents could be converted to diacylfuroxans in a solvent-free reaction by combining the reagents Fe(NO₃)₃·9H₂O and P₂O₅ under high-speed ball milling. This reaction was facile and eco-friendly, and exhibits advantages in terms of better toleration, safety, and easier operation. The nitrate acid and nitrogen dioxide generated in situ should play a major role in this mechanochemical reaction.     

Selective reduction of NOX with C3H6 over Cu incorporated into silicoalumino-phosphate (SAPO)

Cu ion-exchanged SAPO-34 which is a highly active catalyst for selective reduction of NO with C₃H₆, was synthesized and the Cu ion was characterized in the SAPO-34 by ESR, XPS, IR, and XAFS. ESR study indicated that two kinds of Cu(II) with different environments exist in SAPO-34. The Cu(II) species disappeared immediately by C₃H₆ treatment and recovered by oxygen treatment. XAFS study indicated that most of the Cu(II) was reduced to Cu(I) under the presence of C₃H₆. These studies revealed that a selective NO reduction by C₃H₆ over SAPO-34 should proceed by the redox reaction of a copper ion between Cu(I) and Cu(II).     

Synthesis,Structure, and Reactivity of Metal Complexes with Alkoxysilylmethyl Ligands

The synthesis and properties of the new metal complexes 1 , 6 – 12 with alkoxysilylmethy substituents (RO–SiR′₂–CH₂–ML_n) is described. The complexes 14 , 15 and 18 with a chloromethylsiloxy ligand were also prepared. These molecules should serve as starting compounds for the synthesis of metallasilaoxetanes. Several reactions which should lead to these new metallacycles have been performed, but it was never possible to isolate them or to proof their existence spectroscopically. However, chloride abstraction from (C₅H₅)₂Ti(Cl)CH₂Si(CH₃)₂O^tBu ( 7 ) by silver cations led to the activation of the Si–O–R group. This indicates an interaction of the oxygen atom with the metal atom, but there was no proof for the intermediate formation of a four membered metallacycle.     

Theoretical study on the atmospheric reaction of CH3SH with O2

A detailed study on the reaction mechanism of CH₃SH with O₂ was carried out using quantum chemical methods. Eleven singlet pathways and four triplet pathways were found based on CCSD(T)//M06-2x calculations. The nature of chemical bonding evolution was also studied using electron localization function and atoms in molecules analysis. Moreover, reaction rate constants were calculated between 200 and 800 K at the level of the transition state theory by Wigner tunneling correction. The results suggest that the main products should be CH₂SO, H₂O, CH₃OH, SO, CH₄, and SO₂, respectively, basically coinciding with the experimental results. The corresponding feasible pathways are channels R7, R8, and R9, respectively, with an effective energy barrier of 56.21 kJ/mol. Obviously, given the low energy barrier similar to the main paths mentioned above, the products CH₂SH and HO₂ should assume a definite proportion in all possible products, although such species were not yet detected in experiment.     

The hollandite-related structure of Ba2Ti9O20

The crystal structure of Ba₂Ti₉O₂₀ has been determined by comparison of experimental high-resolution electron micrographs with images simulated using structural models deduced from the micrographs in conjunction with crystallochemical principles. The structure consists of lamellae of hollandite-type structure alternating with BaTiO₃-like units, which effectively immobilize the Ba ions. This material should be relatively more leach resistant to attack by aqueous sodium chloride solutions. The structure determination clarifies the observation that this material has unique properties as a microwave resonator, compared with other barium and alkali titanate structures.     

Hydrogenation of Hexene-1 by Gas Phase Spillover Hydrogen. Influence of Substances Added in the Reaction Chamber, Without Contact to the Catalyst

The activation and reaction zone in a gas phase hydrogen spillover experiment were separated by a frit as in [1]. In the activation zone hydrogen was activated by a Pt/Al₂O₃ catalyst, the activated hydrogen reacted in the reaction zone with hexene-1, leading to a strong increase in conversion. A further increase was caused by addition of oxygen into the reaction zone without contact with the catalyst, which may be interpreted as the effect of branched radical chains or an activation of the glass surface. Water does not alter the reaction. NO, a radical capturing substance, lowers the reaction rate, while N₂ shows no effect, an indication that the activation is not caused by vibrationally excited hydrogen, which should be effected similarly by NO and N₂.     

New semiconducting oxide photoanodes for water splitting in a photoelectrochemical cell Electrochemistry of n-type NiTiO3

The electrochemical behaviour of NiTiO₃ has been studied. The interest in this mixed-metal oxide lays in its possible use for solar-energy conversion. Anodic oxidation of NiTi0₃ was very irreversible. The electrode became aged, probably due to formation of a porous film of an irreducible higher oxide. The stirring-independent Cottrell behaviour of the anodic oxidation of NiTiO₃ should be due to current limitation by diffusion of a reaction product away from the NiTi0₃ surface through this irreducible higher oxide, which should be of a porous nature. The diffusion-limiting species could not be OH^?, as the Cottrell slopes only increased by about five times for a pH increase from 3 to 14. Five and two processes were involved in the anodic oxidation of NiTiO₃ at pH 14 and 3 respectively, as determined by chronopotentiometry. The same number of processes appeared upon inversion of the current.     

Unusual Structures of the Parent Molecules Diarsene,Distibene, and Dibismuthene: Toward Their Observation

There is considerable interest, from both experimental and theoretical perspectives, in molecules incorporating multiple bonds between main group elements. Herein, we not only consider the parent molecules HE=EH (E=As, Sb, Bi), but also a number of their isomers. For each E₂H₂ molecule, a number of different structures were optimized with four different DFT methods. Final structures were determined with the coupled cluster method CCSD(T) using large basis sets, namely cc-pVQZ-PP, incorporating relativistic psuedopotentials. All feasible dissociation pathways are examined. For all three E₂H₂ molecules the trans isomer lies lowest in energy, with the cis isomer higher by 2.7 (As), 2.1 (Sb), and 1.8 (Bi) kcal mol⁻¹, respectively. However, both cis and trans structures should be observable, as large barriers (27.7, 20.5, and 17.7 kcal mol⁻¹) separate them. For both the cis and trans structures, in the infrared the strong E-H stretching frequencies should also be observable. Only the cis structures have dipole moments (0.62, 0.01, and 0.83 debye, respectively), and their observation by microwave spectroscopy would be stunning. Also considered were the higher energy vinylidene-like, pyramidal, monobridged, and linear structures. We conclude that molecules such as HSb=SbH-Fe(CO)₄, HBi=BiH-Fe(CO)₄, and related systems, should be feasible synthetic targets.     

Screening of allergic components mediated by H1R in homoharringtonine injection through H1R/CMC‐HPLC/MS

It has been reported that the histamine H₁ receptor (H₁R) gene is up‐regulated in patients with allergic rhinitis and H₁R expression level strongly correlates with the severity of allergy symptoms. Drugs for therapy should avoid allergy symptoms, especially for patients with over‐expressed H₁R. Therefore, screening of the components which could induce H₁R activation is urgently needed for drug safety evaluation. Homoharringtonine injection is a preparation for acute nonlymphocytic leukemia, which is approved by China Food and Drug Administration (CFDA) and US Food and Drug Administration. However, severely adverse reactions often occur with intravenous injection of the preparation. In present study, an H₁R/CMC model was applied for capturing membrane retained components which could induce H₁R activation. Retention components were enriched and analyzed by H₁R/CMC‐HPLC/MS. Homoharringtonine was recognized, separated and identified in homoharringtonine injection. Ca²⁺ flux assay and p‐IP3R expression founded that homoharringtonine retained by the H₁R/CMC model increased phosphorylation of IP3R and promoted cytosolic free Ca²⁺ elevation in a dose‐dependent manner which further verified the activity of homoharringtonine in activating the H₁R. In conclusion, homoharringtonine was screened and identified as a potential allergic factor. This provides an indication that a patient with over‐expressed H₁R should be aware of possible allergic reaction when applying homoharringtonine injection. Copyright © 2014 John Wiley & Sons, Ltd.