N-芳亚甲基-1-丙烯-1-胺与醇钠的反应

研究了N-芳亚甲基-1-丙烯-1-胺与醇钠(甲醇钠,乙醇钠)的加成反应,该反应具有高度的区域选择性,提出了可能的反应机理。     

Preparation of high surface area ZrO2 and ZrO2-Y2O3 from the alkoxide

In order to obtain a catalyst support with a high surface area, ZrO₂ and ZrO₂-Y₂O₃ were prepared by the hydrolytic decomposition of the corresponding isopropoxide dissolved in benzene. The hydrolysis was carried out at 80°C using an excess amount of distilled water in flowing dry nitrogen. The precipitates thus obtained were dried at 100°C followed by calcination at 500°C in air or nitrogen for 1 h. The specific surface areas for both of the ZrO₂ and ZrO₂-Y₂O₃ increased with increasing amount of water added for hydrolysis, and the surface areas for ZrO₂-Y₂O₃ increased with increasing yttrium content. A ZrO₂ having a surface area of 130 m²/g was produced, and a stabilized tetragonal ZrO₂ with 15 mol% Y³⁺ having a surface area of 200 m²/g was produced. Furthermore, despite the difference in the ZrO₂ and ZrO₂-Y₂O₃ crystal structures, the lattice-strain of ZrO₂ has been unequivocally related to the surface area.     

Ultraviolet spectroscopic study of ferric hydroxide complexation

Ultraviolet absorbance spectra of ferric ions in 0.68m NaClO₄ were studied as a function of pH at 4.0, 14.9, and 25.0°C. The results provided an evaluation of the stability constant for the formation of FeOH²⁺ which is *₁=[FeOH ⁺][H ⁺]/[Fe ³⁺]. The enthalpy change for the reaction Fe³⁺+H₂O FeOH²⁺+H⁺ was calculated as 10.0±0.3 kcal-mole^–1. Increasing temperature was also found to promote the reaction Fe³⁺+2H₂O Fe(OH) ₂ ⁺ +2H⁺. Our results were combined with the results of other to produce an expression describing the first hydrolysis equilibrium at ionic strengths between 0 and 3m and temperatures between 4.0 and 45.0°C at 1 atm total pressure. At 25°C and 0.68m the ionic strength *₁=1.90×10^-3     

A promiscuous dicopper(II) system promoting the hydrolysis of bis(2,4‐dinitrophenyl)phosphate: Gaining mechanistic insight by means of structural and spectroscopic DFT studies

Catechol oxidases (COs) are plant enzymes that belong to the oxidoreductases class. They contain a dinuclear copper center in their active site. In this article, we have investigated the dicopper(II) model complex [Cu₂(μ‐OH)(C₂₁H₃₃ON₆)]²⁺ (Complex‐A) under a computational perspective, using the DFT method, since this approach has been very useful in the treatment of bimetallic copper systems. The structural and spectroscopic study of Complex‐A as well as the structural analysis of the BDNPP/Complex‐A (Complex‐B) adduct have been carried out. The calculated parameters for Complex‐A are in good accordance with the experimental X‐ray data. Some remarkable points can be observed from the calculated UV–vis relative excitations. The Complex‐B computed structure verifies its identity as a key intermediate species in the BDNPP hydrolysis mechanism. The Cu^II···Cu^II calculated distance in Complex‐B (3.026 Å) is shorter than the calculated for Complex‐A (3.080 Å); one copper atom is bonded to the oxygen of phosphate [Cu (2)···O64–P] at 2.511 Å. These arguments clearly suggest a monodentate interaction and lead to a new mechanism involving terminal substrate coordination and subsequent intramolecular nucleophilic attack by a bridging hydroxide. Such a hypothesis is completely new in terms of homobimetallic copper systems, and may have important implications regarding the chemistry of several biological dinuclear catalytic sites. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Synthesis and Hydrolysis of Hybridized Silicon Alkoxide: Si(OEt)x(OBut)4-x. Part II: Hydrolysis of the Si(OEt)x(OBut)4-x

The hydrolyzation behavior of the Si(OEt)_x(OBu^t)_4-x synthesized in part I was investigated by gas chromatogram/mass spectrum (GC/MS) technique. In the Si(OEt)_x(OBu^t)_4-x, Si(OEt)(OBu^t)₃ showed more rapid hydrolysis than Si(OEt)₂(OBu^t)₂, especially in the initial stages of the hydrolyzation. The dimer and trimer formations along with the sol-gel course were followed during the hydrolyzation process.     

磷酰化组氨酸形成六配位磷中间体的理论研究

用MNDO方法对磷酰化组氨酸磷上酯交换反应侧链咪唑基所参与的六配位磷机理进行了研究。六配位磷中间体形成后,使咪唑基对面的异丙氧基反应活性提高。当磷上酯交换反应发生时,异丙氧基离去和另一分子醇进攻磷,从咪唑基的对面发生,在能量上和空间上都是有利的。六配位磷机理比较好地解释了咪唑的催化作用。     

一步法合成的FeOOH/黑磷纳米复合材料协同实现体系优异的析氧性能

通过水热法,在黑磷(BP)纳米片表面生长FeOOH纳米材料,制备出FeOOH/BP纳米复合材料。作为电化学析氧反应(OER)催化剂,该复合材料在20 mA·cm^-2时的过电位仅为191 mV,Tafel斜率为49.9 mV·dec^-1;在循环1 000圈后,过电位仅仅增加了3 mV,且循环过程中元素价态不变,表现出优秀的稳定性。纳米FeOOH负载于BP表面,客观上能隔断氧气对BP的氧化,保护BP的载流子传导性能。同时,生长的FeOOH颗粒尺度小,结晶性弱,这有利于丰富其活性位点,增大活性面积。     

电感耦合等离子体发射光谱法测定二氧化铀中痕量磷和硅元素

研究了电感偶合等离子体发射光谱法测定二氧化铀(UO2)中痕量磷和硅元素含量的方法。经过对HNO3,H2O等试剂的多级纯化,获得超低空白的高纯试剂。对样品溶解、待测杂质元素与铀基体分离等过程从机理方面进行了研究。在分离铀基体与硅元素时用磷酸三丁酯(TBP)作萃取剂,二甲苯作为稀释剂;在分离铀基体与磷元素时用三辛胺(TOA)作萃取剂,二甲苯作稀释剂。二氧化铀中磷、硅元素检出限分别为0.012,0.078μg/g,加标回收率分别为98%,96%,相对标准偏差小于4%(n=6)。该方法重现性好、检出限低,满足生产和科研检测要求。     

Sol-gel preparation and spectroscopic study of the pyrophanite MnTiO_3 nanoparticles

Titanium dioxide (TiO2) is one of the green cata-lysts, which has attracted much attention due to its promising applications in the purification of air, the bactericidal action of water, and environmental photocatalytic degradation of organic pollutant co…     

甲基三氯硅烷水解反应机理的密度泛函研究

采用量子化学密度泛函方法研究了甲基三氯硅烷的结构性质和水解反应机理,发现水的O原子进攻Si原子取代Cl原子的同时,水的另一个H原子逐渐与Cl结合形成相应的羟基硅烷和HCl.甲基三氯硅烷水解按亲核取代--消除的协同反应机理完成.     

氧空位和磷掺杂协同增强铁钴基材料电解水催化性能

为了研发高效、稳定的电解水催化剂,我们以氧空位和磷掺杂为基础,通过原位浸泡生长和两步热处理的方法,在泡沫铁上合成具有氧空位和磷掺杂的纳米花结构作为析氢反应(HER)和析氧反应(OER)双功能电催化剂。CoFe₂O₄已被报道为一种很有前途的OER和氧还原反应(ORR)电催化剂,然而CoFe₂O₄在HER中表现出电导率差、电催化反应慢的特性。CoFe₂O₄中氧空位(Ov)的形成可以有效调控催化剂表面的电子结构,有助于产生更多的缺陷和空位,从而提高OER的活性。随后,引入磷原子填充在空位中,制备的P-Ov-CoFe₂O₄/IF在碱性电催化测试中展现出优异的HER和OER性能,在10 mA·cm^-2电流密度下HER和OER过电位仅为54和191 mV,Tafel斜率分别为57和54 mV·dec^-1,并具有良好的循环稳定性。     

Binuclear and polymeric Hg(II) complexes of an ambidentate phosphorus ylide: Synthesis,crystal structure,antibacterial activity,and theoretical studies

The new α-keto-stabilized phosphorus ylide Ph₃PCHC(O)PhCN ( Y ) was synthesized by addition of triphenylphosphine to 2-bromo-4′-cyanoacetophenone, followed by treatment with NaOH 10%. Reaction of ligand ( Y ) with methanolic solution of mercury(II) halides under mild conditions yielded the binuclear complexes [Y·HgX₂]₂ [X=Cl ( 1 ), Br ( 2 ), I ( 3 )]. The new organic/inorganic composite polymer [Hg(NO₃)₂(Y)]_n ( 4 ) was synthesized by the reaction of mercury(II) nitrate with the phosphorus ylide Y . Compounds synthesized were characterized by Fourier-transform infrared, ¹H, ³¹P, and ¹³C nuclear magnetic resonance spectroscopic methods, which confirmed the coordination of ylide to the metal center through the ylidic carbon atom. Single-crystal X-ray structures of phosphorus ylide Y and polymeric complex 4 were also determined and the crystallographic data of complex 4 showed that the title complex has an infinite one-dimensional structure. Furthermore, the electronic and molecular structures of complexes 1 – 3 were investigated at the BP86/def2-SVP level of theory, indicating an increasing trend for C→M bond lengths: Hg₂I₂ > Hg₂Br₂ > Hg₂Cl₂ in [Y→HgX₂]₂ (X = Cl, Br, I) complexes. In addition, the antibacterial activity of ligand Y and all complexes using the agar disc diffusion method was examined against both selected gram-positive and gram-negative bacteria. Results indicated that the ligand Y and complexes 1 and 4 show good antibacterial effect against gram-positive bacteria tested; besides, the inhibition zones of complexes were significantly larger than those of chloramphenicol as standard.     

Theoretical study on the degradation mechanism of methamidophos and chloramine phosphorus with OH radicals

Theoretical investigation on the gas‐phase degradation reaction mechanism of methamidophos (MAP) and chloramine phosphorus (CHP) with OH radicals is performed. The equilibrium geometries and the harmonic vibration frequencies of the stationary points are obtained at M06‐2x/6‐31+G(d,p) level, and the higher‐level energetic information is further refined at M06‐2x/6–311++G(3df,2p) level. The rate constants for the 14 reaction channels are calculated by the improved canonical variational transition state theory with small‐curvature tunneling correction over the temperature range 200–2000 K. The three‐parameter expressions of k₁(T) = 1.53 × 10^?19T^2.74exp(?1005.12/T), k₂(T) = 1.36 × 10^?20T^3.02exp(?1259.56/T) are given. The total rate constants of all reaction channels of MAP with OH radicals are in good agreement with the available experimental data. Our results indicate that the H‐abstraction reactions on methyl are the major channels for the reaction of MAP and CHP with OH radicals. © 2015 Wiley Periodicals, Inc.     

A first‐principles study of diatomic NiAl: Ground state,structure, and spectroscopic constants

A computational study of diatomic NiAl is reported. Molecular properties evaluated include the equilibrium bond length (r_e), equilibrium stretching frequency (ω_e), doublet‐quartet energy splitting, and nickel‐aluminum bond strength. Several interesting conclusions have resulted from this research. First, convergence in calculated properties is smoother with recently reported correlation consistent basis sets than earlier basis sets for Ni and Al. Second, with the exception of bond strength, basis set limit properties extrapolated using correlation basis sets are in agreement with reported data. Third, this research suggests that caution may be needed with regard to the use of DFT for developing interatomic potentials for larger scale simulations. For example, B97‐1 showed better agreement with reported r_e for ²NiAl than B3LYP. However, the situation was reversed for the calculation of ω_e. With respect to bond strength, the situation is unclear due to the scatter among experiment and calculations. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Molecular interaction study of the diisopropyl ether-propionic acid mixture by spectroscopic and dielectric studies

FTIR and 13C NMR spectral studies have been carried out on diisopropyl ether-propionic acid binary mixture to probe the molecular interactions and stoichiometry of complexation. Density functional theory (DFT) calculations of vibrational frequencies of pure acid and ether-acid binary mixtures have also been performed. In addition, Kirkwood-correlation factors, excess permittivity and excess free energy of mixing have been obtained at various concentrations and at four different temperatures from the dielectric measurements. Excess permittivity is found to have positive deviation and excess free energy deviates negatively from ideal behaviour.     

Theoretical study of tetrahydrofuran: Comparative investigation of spectroscopic and structural properties between gas and liquid phases

Rovibrational spectroscopic constant of tetrahydrofuran (THF) dimer have been calculated starting from three potential energy curves, each one obtained in a different way: (i) by ab initio calculations at MP2/aug‐cc‐pVDZ level; (ii) using Lennard‐Jones liquid parameters available in the literature, and (iii) from the pair obtained through Monte Carlo Simulation of liquid THF. The comparison among these results allowed the characterization of many solvent effect contributions. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Hydrolysis of cyclic phosphates by ribonuclease A: a computational study using a simplified ab initio quantum model

The second step in the enzyme-catalyzed hydrolysis of phosphate esters by ribonuclease A (RNase A) was studied using an ab initio quantum-based model of the active site including constrained parts of three critical residues, His-12, His-119, and Lys-41, and a small substrate. The competition between release of the cyclic phosphate intermediate and subsequent hydrolysis following transphosphorylation was explored to determine the electronic factors that contribute to preferential intermediate product release observed experimentally. The structural and energetic results obtained at both the RHF and MP2 levels reveal several contributing factors consistent with experimental observation. Although the intrinsic electronic effects tend to favor hydrolysis slightly with an overall activation free energy of approximately 70 kJ mol(-1), entropic and environmental effects favor release of the cyclic phosphate intermediate over hydrolysis. Exploration of the second, hydrolysis step also revealed interesting similarity with the transphosphorylation step, including the observation of autocatalysis by the substrate. Moreover, both steps of the overall RNase A reaction reveal multiple pathways involving proton transfers to sites of similar proton affinities. The anionic phosphate in both steps can act as a stable proton binding site as protons are moved around the active site throughout the progress of the reaction. These results suggest autocatalysis may be representative of more general behavior in enzymes containing highly charged substrates, especially phosphates.     

Addition reactions of a phosphorus triamide to nitrosoarenes and acylpyridines

Abstract

Tricoordinate phosphorus compounds react with a wide variety of double bonds through addition reactions. The dipolar and cyclic products formed are important intermediates in organophosphorus chemistry. We investigated the reactivity between phosphorus triamide 1 and nitrosoarenes and 2-acylpyridines. For sterically congested substrates, the formation of σ⁵ Aroyan, C. E.; Dermenci, A.; Miller, S. J. The Rauhut–Currier Reaction: A History and Its Synthetic Application. Tetrahedron 2009, 65, 4069–4084. DOI: 10.1016/j.tet.2009.02.066.[Crossref], [Web of Science ®] , [Google Scholar],λ⁵-phosphorus products is observed. DFT calculations indicate this product is formed through a concerted [4?+?1] mechanism. For less sterically congested substrates, products are observed arising from cleavage of the N?=?O or C?=?O bond with formation of a terminal P?=?O bond and aryl nitrene or carbene migration into a P–N bond of the phosphorus triamide core. DFT calculations are consistent with an initial [2?+?1] addition to phosphorus followed by formal carbene/nitrene migration in these cases.     

Fundamental studies of novel inorganic–organic charged zwitterionic hybrids: 3. New hybrid charged mosaic membranes prepared by modified metal alkoxide and zwitterionic process

A series of novel hybrid charged mosaic membranes have been prepared through a coupling reaction and zwitterionic process. This kind of coupling reaction was conducted between phenylaminomethyl trimethoxysilane (PAMTMS) and Ti(O-nBu)₄ modified by acetylacetone, which was proved by FTIR spectra and the conventional properties of the membranes. Ion-exchange capacity (IEC) measurements indicate that both anion-exchange capacities (an-IECs) and cation-exchange capacities (cat-IECs) of the membranes coated one to three times are in the range of 4.62 × 10⁻⁴ to 1.48 × 10⁻² and 1.57 × 10⁻² to 3.2 × 10⁻² meq. cm⁻², respectively; while these IECs increase with the elevating Ti-content. Streaming potentials exhibit that the isoelectric points (IEPs) of the membranes coated one time are in the range of pH 6–7.5 and decrease with the increasing Ti-content; but for those coated two times, the IEPs are in the range of pH 6–7.0 and increase with the rising Ti-content. Water content demonstrates a decline tendency with the rising pH whether for the membranes coated one or two times. Pure water flux reveals a downward trend with both the increasing coating times and the ingredients of hybrid precursors. The surface morphologies of the membranes coated three times show that the membrane microstructures can be affected by the compositions of coating solutions, while cross-section SEM images suggests that the membrane thickness elevates with the increasing coating times.