A Computational Study of the Combinatorial Addition of Oxygen to Buckminsterfullerene

All possible isomers of C₆₀O _x have been investigated for x=1, 2, and 3. The method used is a modified extended Hückel method. There is a single C₆₀O isomer, 8 unique C₆₀O₂ isomers, and 47 unique C₆₀O₃ isomers. It is found that a single C₆₀O₂ isomer is much more stable than the remaining 7 and that 3 C₆₀O₃ isomers are more stable than the remaining 44. A qualitative reason for these results is proposed. The results indicate that the three lowest-energy C₆₀O₃ isomers should exist in equilibrium at room temperature.     

臭氧氧化结合湿法喷淋对玻璃窑炉烟气同时脱硫脱硝实验研究

采用臭氧氧化结合湿法喷淋对模拟玻璃窑炉烟气开展了同时脱硫脱硝实验研究.采用不同溶液(NaOH、Na₂S)进行了喷淋实验.结果表明,保证溶液pH值在10以上,NaOH浓度对NO_x脱除效率无影响,SO₂的存在促进了NO_x吸收.当O₃/NO物质的量比为1.6、溶液NaOH浓度为0.5%时,NO_x脱除效率可达70%,SO₂脱除效率在99%以上.往喷淋液中添加Na₂S,NO_x脱除效率随Na₂S浓度增加而提高,SO₂的存在对NO_x脱除效率无影响.当O₃/NO物质的量比为1.2、溶液中NaOH浓度为0.5%、添加剂Na₂S浓度为0.6%时,NO_x脱除效率可达70%,SO₂脱除效率在95%以上.60 min长时间运行实验证明,模拟烟气中的NO_x经碱液和添加剂吸收后主要以NO^-₂的形式存在于喷淋液中,且NO_x脱除效率不随溶液pH值的变化而变化.     

Calcium-containing cathodic material for solid oxide fuel cells

Using the citrate sol-gel method, a new complex oxide Ca_0.75Y_0.25Co_0.15Mn_0.85O_2.92 is synthesized. It is shown that this compound is crystallized in the rhombically distorted version of perovskite structure (a = 0.53397(8), b = 0.7470(1), c = 0.52810(6) nm). The phase is characterized by a low coefficient of thermal expansion (CTE) (13.8 ppm K^?1) and high electric conductivity (135 S/cm at 900°C). The chemical reaction between Ca_0.75Y_0.25Co_0.15Mn_0.85O_2.92 and the YSZ and GDC electrolyte materials is studied. The material is highly reactive and reacts with YSZ and GDC at 900°C and 1070°C, respectively. It is concluded that Ca_0.75Y_0.25Co_0.15Mn_0.85O_2.92 is a promising cathodic material for solid oxide fuel cells, provided a reliable protection SDC sublayer is formed between the cathode and the YSZ membrane.     

Efficient Reduction of Aryl Azides and Aryl Nitro Compounds to Their Corresponding Amines with Sulfurated Calcium Borohydride CA(BH2S3)2. A New Modified Borohydride Agent

Ca(BH₂S₃)₂ is easily prepared by metathetical reaction between NaBH₂S₃ and CaCl₂ in THF. Ca(BH₂S₃)₂ is much more stable than NaBH₂S₃ therefore, is a more practical reagent. Sulfurated calcium borohydride can easily reduce aryl nitro and aryl azido functions to their amines in high yields in refluxing THF. Reduction of nitro groups is accompanied with regioselectivity. Very high chemoselectivity is also observed for the reduction of an azido functional group in the presence of nitro functionality.     

Complex copper(II) fluorides. XV. The Ternary System BaF2?CuF2?ScF3

The liquid-solid phase diagram of the binary system BaF₂? ScF₃ is established by D.T.A. and radiocrystallography. Three fluorides are disclosed: Ba₃Sc₂F₁₂, Ba₅Sc₃F₁₉ and a cubic high temperature phase Ba_1?xSc_xF_2+x (x = 0.17), the structure of which derives from that of BaF₂. A solid solution between BaF₂ and ScF₃ is also evidenced at high temperature. The ternary system BaF₂? CuF₂? ScF₃ is investigated by radiocrystallography and an isothermal section at 670°C is given. It shows the existence of four phases: a complex quaternary fluoride Ba₁₀Cu₁₂ScF₄₇, two “polytypic” phases the structure of which derives from that of BaCuF₄ and a tetragonal solid solution Ba₅Sc_3?xCu_xF_19?x with 0 ≤ x ≤ 1.     

Metal–Organic Framework (MOF)-Derived Carbon-Mediated Interfacial Reaction for the Synthesis of CeO2−MnO2 Catalysts

CeO₂-based catalysts are widely studied in catalysis fields. Developing one novel synthetic approach to increase the intimate contact between CeO₂ and secondary species is of particular importance for enhancing catalytic activities. Herein, an interfacial reaction between metal–organic framework (MOF)-derived carbon and KMnO₄ to synthesize CeO₂−MnO₂, in which carbon is derived from the pyrolysis of Ce-MOFs under an inert atmosphere, is described. The MOF-derived carbon is found to restrain the growth of CeO₂ crystallites under a high calcination temperature and, more importantly, intimate contact within CeO₂/C is conveyed to CeO₂/MnO₂ after the interfacial reaction; this is responsible for the high catalytic activity of CeO₂−MnO₂ towards CO oxidation.     

Catalysis of heteropoly acidic salts for synthesis of diethylene glycol ethyl ether with diethylene glycol and ethanol

Ag₃PW₁₂O₄₀ and Ag₄SiW₁₂O₄₀ showed high activity and stability in the synthesis of diethylene glycol ethyl ether with diethylene glycol and ethanol, on which the conversion is 80.2% and 78.4%, respectively, and the selectivity of diethylene glycol ether is 75.4% and 80.6%, respectively. After the third reaction cycle, Ag₃PW₁₂O₄₀ and Ag₄SiW₁₂O₄₀) still showed higher activity and selectivity, on which the conversion is 72. 6% and 77.5% respectively. But the activity of Ag₃PMo₁₂O₄₀ is lower, the conversion is only 21.0%. IR, XRD, TG and n‐butylamine titrimetry showed that the catalysis may be connected with two kinds of acidic centers owned by heteropoly acidic salt.     

Bildung siliciumorganischer Verbindungen. 89. Selektive Photobromierung von Si-methylierten Carbosilanen

Formation of Organosilicon Compounds. 89. Selective Photobromination of Si-methylated Carbosilanes A selective photobromination of the C atoms in the skeleton of Si-methylated carbosilanes is reported. (me₃Si? CH₂)₂Sime₂ reacts to me₃Si? CBr₂? Sime₂? CH₂? Sime₃ in good yields (me = CH₃); the second CH₂ group is considerably slower brominated. Photobromination of (me₂Si? CH₂)₃ consecutively yields a and b . Also from (me₂Si? CH₂)₄ the derivative with one CBr₂ group is accessible. Bromination of tertiary CH groups is highly preferred; this is shown by the selective formation of c . The C-bromination of SiBr-substituted carbosilanes is significantly more difficult; nevertheless (Brme₂Si)₂CH₂ selectively forms (Brme₂Si)₂CBr₂. Brme₂Si? CH₂? Sime₂? CH₂? Sime₃ forms Brme₂Si? CH₂? Sime₂? CBr₂? Sime₃, i. e., only the CH₂ group non-adjacent to SiBr is attacked. The formation of CHBr groups could not be detected. Higher temperatures and longer reaction times increase the formation of polymers.     

Substituent effects on the disproportionation—combination rate constant ratios for gas‐phase halocarbon radicals,Part 5: Reactions of CF3 + CF3CH2CHCH3 and CF3CH2CHCH3 + CF3CH2CHCH3

Rate constant ratios, k_d/k_c for the disproportionation/combination reaction have been measured as 0.07 ± 0.02 when an H is removed from the CH₂ position of the CF₃CH₂CHCH₃ radical and as 0.24 ± 0.03 when the H is removed from the CH₃ position in the reaction with the CF₃ radical. For the self‐reaction between two CF₃CH₂CHCH₃ radicals, k_d/k_c has been measured as 0.27 ± 0.03 when the H is removed from the CH₂ position and as 0.47 ± 0.04 when the H is removed from the CH₃ position. The branching fraction, corrected for the number of hydrogens at each site, is 0.70 favoring the methyl position when the acceptor radical is CF₃ and 0.54 when CF₃CH₂CHCH₃ is the acceptor radical. Branching fraction results show that the CF₃ substituent on the CF₃CH₂CHCH₃ radical hinders disproportionation when CF₃ is the acceptor radical. When the accepting radical is CF₃CH₂CHCH₃ the CF₃ substituent may slightly impede the disproportionation reaction, but the branching ratio is nearly statistical. The effect of substituents on the donor radical, CF₃CH₂CHX, will be discussed for the series X = H, CF₃, Cl, and CH₃ when the acceptor radical is CF₃. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 549–557, 2001     

Oxidative Dehydrogenation of 1-Butene Over Magnetite

Magnetite (FC₃O₄), a partially reduced iron oxide, has long been considered as inactive in the oxidative dehydrogenation of butene. By studying a clean Fe₃O₄ powder, we found that Fe₃O₄, similar to other spinel ferrites, is not only active, but also more active and selective than α-Fe₂O₃. The active site densities and the desorption temperatures of oxidation products on Fe₃O₄ were also measured. Fe₃O₄ is, however, unstable under flow reaction conditions. Even if the bulk of the oxide is stabilized in the form of Fe₃O₄ at high temperatures and low O₂/C₄ ratios, its surface is gradually oxidized to a form close to α-Fe₂O₃, resulting in a decrease in both the activity and selectivity. The restructuring of the FC₃O₄ surface is temperature dependent. At 300°C, the high selectivity and activity of a low-surface-area Fe₃O₄ can be long preserved even if the bulk is oxidized to α-Fe₂O₃.     

Formation mechanisms of Si3N4 and Si2N2O in silicon powder nitridation

Commercial silicon powders are nitrided at constant temperatures (1453 K; 1513 K; 1633 K; 1693 K). The X-ray diffraction results show that small amounts of Si₃N₄ and Si₂N₂O are formed as the nitridation products in the samples. Fibroid and short columnar Si₃N₄ are detected in the samples. The formation mechanisms of Si₃N₄ and Si₂N₂O are analyzed. During the initial stage of silicon powder nitridation, Si on the outside of sample captures slight amount of O₂ in N₂ atmosphere, forming a thin film of SiO₂ on the surface which seals the residual silicon inside. And the oxygen partial pressure between the SiO₂ film and free silicon is decreasing gradually, so passive oxidation transforms to active oxidation and metastable SiO(g) is produced. When the SiO(g) partial pressure is high enough, the SiO₂ film will crack, and N₂ is infiltrated into the central section of the sample through cracks, generating Si₂N₂O and short columnar Si₃N₄ in situ. At the same time, metastable SiO(g) reacts with N₂ and form fibroid Si₃N₄. In the regions where the oxygen partial pressure is high, Si₃N₄ is oxidized into Si₂N₂O.     

Photolytically Induced Reaction of Monomeric AlCl with Dihydrogen in a Solid Ar Matrix at 12 K: Generation and Characterization of the Previously Unknown Monomeric Aluminium Hydride ClAlH2

Monomeric AlCl is shown to react with H₂ under photoactivation to yield the new monomeric aluminium hydride ClAlH₂. The planar, C_2v symmetric molecule is characterized by its IR spectra, taking in the effects of isotopic substitution (H₂, D₂ and HD), allied with detailed quantum chemical calculations. A normal coordinate analysis is performed to calculate accurate force constants. The properties of this species are compared to the ones of other related compounds featuring either an Al‐H or an Al‐Cl bond. Finally, the dimerization to give the D_2h symmetric H₂Al(μ‐Cl)₂AlH₂ is investigated theoretically. This dimer is of interest as a possible reagent to prepare dialane, Al₂H₆. The enthalpy for the reaction of H₂Al(μ‐Cl)₂AlH₂ in the gas‐phase with solid LiAlH₄ to give gaseous Al₂H₆ and solid LiCl is calculated.     

New process for preparing aqueous solutions of Mo-V-phosphoric heteropoly acids

A new ecofriendly process is proposed for the synthesis of aqueous solutions of Mo-V-phosphoric Keggin heteropoly acids H_{3 + x} PV _x Mo_{12 ? x} O₄₀(HPA_?x ). First, V₂O₅ is dissolved in cooled H₂O₂ to form peroxyvanadium compounds, which then spontaneously decompose to yield the H₆V₁₀O₂₈ solution. The latter is stabilized by the addition of H₃PO₄ to yield an H₉PV₁₄O₄₂ solution. This solution is gradually added to a boiling H₃PO₄ + MoO₃ aqueous suspension. This suspension is gradually evaporated that is followed by dissolution of MoO₃ to produce an HPA_?x solution. This process is reliable and almost non-waste and is promising for preparing HPA_?x solutions with x = 2–6 on pilot and large scales.     

Investigation of CF2 carbene on the surface of activated charcoal in the synthesis of trifluoroiodomethane via vapor-phase catalytic reaction

This paper investigates the synthetic mechanism of trifluoroiodomethane (CF₃I) in the reaction of trifluoromethane and iodine via vapor-phase catalytic reaction. It is suggested that CF₂ carbene is the key intermediate and is formed in the pyrolysis process of CHF₃ at high temperature. However, in pyrolysis of CHF₃ under activated charcoal (AC) existing conditions, no C₂F₄ was detected. H₂ and 2-methyl-2-butene could not trap the CF₂ carbene. When treating the remained compounds on the used AC with H₂, CH₄ is formed on the process. It is proposed that CF₂ carbene combines with AC strongly and transfers into CF₃ radical on heat. In addition, it is found that the AC is not only the catalyst supporter to form CF₃I, but also a co-catalyst to promote the formation of CF₂ carbene and CF₃ radical.     

Thermodynamically Favourable States in the Reaction of Nitrogenase without Dissociation of any Sulfide Ligand

We have used combined quantum mechanical and molecular mechanical (QM/MM) calculations to study the reaction mechanism of nitrogenase, assuming that none of the sulfide ligands dissociates. To avoid the problem that there is no consensus regarding the structure and protonation of the E₄ state, we start from a state where N₂ is bound to the cluster and is protonated to N₂H₂, after dissociation of H₂. We show that the reaction follows an alternating mechanism with HNNH (possibly protonated to HNNH₂) and H₂NNH₂ as intermediates and the two NH₃ products dissociate at the E₇ and E₈ levels. For all intermediates, coordination to Fe6 is preferred, but for the E₄ and E₈ intermediates, binding to Fe2 is competitive. For the E₄, E₅ and E₇ intermediates we find that the substrate may abstract a proton from the hydroxy group of the homocitrate ligand of the FeMo cluster, thereby forming HNNH₂, H₂NNH₂ and NH₃ intermediates. This may explain why homocitrate is a mandatory component of nitrogenase. All steps in the suggested reaction mechanism are thermodynamically favourable compared to protonation of the nearby His-195 group and in all cases, protonation of the NE2 atom of the latter group is preferred.     

MnS-Ln2S3 (Ln = La, Nd, or Gd) phase diagrams; thermodynamics of phase transitions

The MnS-La₂S₃ phase diagram has been constructed where the incongruently melting compound Mn₂La₆S₁₁ is formed. Complex sulfide Mn₂La₆S₁₁ is characterized by monoclinic structure; its incongruent melting temperature is 1535 K. Eutectic coordinates are 31 mol % La₂S₃, 1490 K. The extent of the ??-La₂S₃ based solid solutions at 1570 K is 8 mol % MnS; at 770 K, ??-La₂S₃ dissolves 3 mol % MnS. The MnS-Gd₂S₃ system is a eutectic with limited solid solutions. Eutectic coordinates are 35.5 mol % Gd₂S₃, 1640 K. Solubility in ??-Gd₂S₃ is 28 mol % MnS at 1570 K, in ??-Gd₂S₃ is 13 mol % MnS at 1170 K, and in MnS is 1 mol % Gd₂S₃. Thermochemical equations have been composed for eutectic and eutectoid phase transformations. A MnS-Nd₂S₃ phase diagram has been predicted.     

The Effect of MoO3 Addition to V2O5/Al2O3 Catalysts for the Selective Catalytic Reduction of NO by NH3

The effect of MoO₃ addition to alumina supported vanadia catalysts on the catalytic activity for the selective catlaytic reduction of NO is investigated. Upon the addition of MoO₃, catalytic activity is enhanced and the particle size of V₂O₅ which is shown by the results of XRD and Raman spectroscopy is decreased. The MoO₃-V₂O₅/Al₂O₃ catalyst also exhibits more resistance to SO₂ deactivation than V₂O₅/Al₂O₃ does.     

A convenient method to reduce hydroxyl-substituted aromatic carboxylic acid with NaBH4/Me2SO4/B(OMe)3

The reduction of hydroxyl-substituted aromatic carboxylic acid with NaBH₄/Me₂SO₄/B(OMe)₃ is described. Borane is generated by the reaction of NaBH₄ with Me₂SO₄ in THF, which is as efficient as the commercial one. B(OMe)₃ has been successfully applied to increase the reactivity and selectivity of this reaction. The optimum ratio of borane/B(OMe)₃/acid is studied, and a variety of hydroxyl-substituted aromatic acids are reduced in good yields.     

白钨酸研究——Ⅶ.K3W2Cl9的制备及反应

用粉状白钨酸作原针,在一般条件下制备K₃W₂Cl₉,产率达53%,证明白钨酸是比黄钨酸优越的钨化学试剂。研究了K₃W₂Cl₉经离子又换转化为酸的形态后与Ndz₂(C0₃)₃的反应。得到了新的化合物NdW₂Cl₉,提出了一条新的制备溶解度大的各种金属离子与W₂Cl₉^3-的化合物的途径。 对K₃W₂Cl₉和NdW₂Cl₉进行了紫外可见尤谱和X针线粉末衍射的测定。     

Concomitant Carboxylate and Oxalate Formation From the Activation of CO2 by a Thorium(III) Complex

Improving our comprehension of diverse CO₂ activation pathways is of vital importance for the widespread future utilization of this abundant greenhouse gas. CO₂ activation by uranium(III) complexes is now relatively well understood, with oxo/carbonate formation predominating as CO₂ is readily reduced to CO, but isolated thorium(III) CO₂ activation is unprecedented. We show that the thorium(III) complex, [Th(Cp′′)₃] ( 1 , Cp′′={C₅H₃(SiMe₃)₂‐1,3}), reacts with CO₂ to give the mixed oxalate‐carboxylate thorium(IV) complex [{Th(Cp′′)₂[κ²‐O₂C{C₅H₃‐3,3′‐(SiMe₃)₂}]}₂(μ‐κ²:κ²‐C₂O₄)] ( 3 ). The concomitant formation of oxalate and carboxylate is unique for CO₂ activation, as in previous examples either reduction or insertion is favored to yield a single product. Therefore, thorium(III) CO₂ activation can differ from better understood uranium(III) chemistry.