硼中子捕获疗法中使用的1,2-C2B10H12异腈衍生物的结构和电子特性

利用密度泛函方法在B3LYP/6-31G(d)水平上对1,2-C2B10H12的两种异腈类衍生物的结构特性进行了研究. 结果表明, 1,2-C2B10H11NC的活性较强; 1,2-C2B10H11NC和1,2-C2B10H11CH2NC可以通过结构中的C4原子与过渡金属原子成键而形成碳硼烷异腈金属配合物. 1,2-C2B10H11NC和1,2-C2B10H11CH2NC的分子极性均比1,2-C2B10H12的弱, 这不利于它们在硼中子捕获疗法中的应用.     

Computational elucidation of mechanisms of alkaline hydrolysis of nitrocellulose: dimer and trimer models with comparison to the corresponding monomer

Density functional theory (DFT) investigation has been undertaken to explore alkaline hydrolysis mechanisms for nitrocellulose in the gas phase and in bulk water solution by considering the dimer and trimer forms of 2,3,6-trinitro-β-d-glucopyranose in the (4)C(1) chair conformation and by comparing the computed results with the monomer. Ground and transition state geometries were optimized using the B3LYP functional and the 6-311G(d,p) basis set both in the gas phase and in the bulk water solution. The nature of respective potential energy surfaces was ascertained through harmonic vibrational frequency analysis. Intrinsic reaction coordinate calculations were performed to ensure that computed transition state connects to the respective reactants and products. Single-point energy calculations were also performed using the recently developed M06-2X functional and the cc-pVTZ basis set using the B3LYP/6-311G(d,p) optimized geometries. Effect of the bulk water solution was modeled using the polarizable continuum model (PCM) approach. It has been suggested that the dimeric form of 2,3,6-trinitro-β-d-glucopyranose can be considered as the smallest model to study the nitrocellulose system regarding the alkaline hydrolysis reaction. It was predicted that the peeling-off reaction will start after the denitration of various sites, which will follow a C3 → C6 → C2 denitration route. Further, it was determined that the peeling-off reaction will be more preferred than the ring cleavage through the ring CO bond.     

XPS spectra of some transition metal and alkaline earth monochalcogenides

The first-row transition-metal monosulfides and alkaline-earth chalcogenides were studied by means of X-ray photoelectron spectroscopy. It is shown that the bonding in the alkaline earth compounds is relatively ionic with XPS evidence for significant charge separation. On the other hand, transition metal sulfides, with the exception of MnS, appear to be principally metallic with little or no charge separation. Values for the inner orbital binding energy shifts are reported for a large number of monochalcogenides.     

金属石墨层间化合物的量子化学和热力学研究

采用量子化学密度泛函B3LYP方法,对碱金属、碱土金属和过渡金属石墨层间化合物(A-GIC,AE-GIC和T-GIC)进行计算.从原子净电荷、Mulliken重叠布居和轨道电子数等角度讨论了A-GIC和AE-GIC的电子结构与成键特性,初步阐明了结构与性能的关系.根据计算结果,结合热力学分析,讨论实验上尚未知的过渡金属石墨层间化合物合成的可能性.     

Alkaline proteins of Bacillus subtilis: first steps towards a two-dimensional alkaline master gel

The genomic sequence of Bacillus subtilis, which is the best studied Gram-positive bacterium, enabled us to obtain a theoretical two-dimensional (2-D) map, demonstrating that about one-third of this proteome has a theoretical alkaline isoelectric point (pI). This represents an important part of the entire proteome, which is not detectable in conventional 2-D gels (pH range 4-7). Sequence analysis revealed that 91% of the ribosomal proteins and a high amount of theoretical membrane proteins should be localized in the alkaline pH range requiring different protein extraction procedures. In order to find the pH range which gives the best resolution results for the alkaline proteins of B. subtilis, immobilized pH gradients (IPGs) with different pH ranges (pH 6-10, 6-11, 4-12, 9-12, and 3-10) were tested and optimized for IPG 4-12. Here we present a version of a first alkaline master 2-D gel for B. subtilis, which is a further complement of the already existing master gel (pH 4-7) in the Sub2D database. Almost 150 spots could be detected and 41 proteins have already been identified.     

Ultra‐high performance supercritical fluid chromatography of lignin‐derived phenols from alkaline cupric oxide oxidation

Traditional chromatographic methods for the analysis of lignin‐derived phenolic compounds in environmental samples are generally time consuming. In this work, an ultra‐high performance supercritical fluid chromatography method with a diode array detector for the analysis of major lignin‐derived phenolic compounds produced by alkaline cupric oxide oxidation was developed. In an analysis of a collection of 11 representative monomeric lignin phenolic compounds, all compounds were clearly separated within 6 min with excellent peak shapes, with a limit of detection of 0.5–2.5 μM, a limit of quantification of 2.5–5.0 μM, and a dynamic range of 5.0–2.0 mM (R² > 0.997). The new ultra‐high performance supercritical fluid chromatography method was also applied for the qualitative and quantitative analysis of lignin‐derived phenolic compounds obtained upon alkaline cupric oxide oxidation of a commercial humic acid. Ten out of the previous eleven model compounds could be quantified in the oxidized humic acid sample. The high separation power and short analysis time obtained demonstrate for the first time that supercritical fluid chromatography is a fast and reliable technique for the analysis of lignin‐derived phenols in complex environmental samples.     

Limits for alkaline detoxification of dilute-acid lignocellulose hydrolysates

In addition to fermentable sugars, dilute-acid hydrolysates of lignocellulose contain compounds that inhibit fermenting microorganisms, such as Saccharomyces cerevisiae. Previous results show that phenolic compounds and furan aldehydes, and to some extent aliphatic acids, act as inhibitors during fermentation of dilute-acid hydrolysates of spruce. Treatment of lignocellulose hydrolysates with alkali, usually in the form of overliming to pH 10.0, has been frequently employed as a detoxification method to improve fermentability. A spruce dilute-acid hydrolysate was treated with NaOH in a factorial design experiment, in which the pH was varied between 9.0 and 12.0, the temperature between 5 and 80°C, and the time between 1 and 7 h. Already at pH 9.0, >25% of the glucose was lost when the hydrolysate was treated at 80°C for 1 h. Among the monosaccharides, xylose was degraded faster under alkaline conditions than the hexoses (glucose, mannose, and galactose), which, in turn, were degraded faster than arabinose. The results suggest that alkali treatment of hydrolysates can be performed at temperatures below 30°C at any pH between 9.0 and 12.0 without problems with sugar degradation or formation of inhibiting aliphatic acids. Treatment with Ca(OH)₂ instead of NaOH resulted in more substantial degradation of sugars. Under the harsher conditions of the factorial design experiment, the concentrations of furfural and 5-hydroxymethylfurfural decreased while the total phenolic content increased. The latter phenomenon was tentatively attributed to fragmentation of soluble aromatic oligomers in the hydrolysate. Separate phenolic compounds were affected in different ways by the alkaline conditions with some compounds showing an increase in concentration while others decreased. In conclusion, the conditions used for detoxification with alkali should be carefully controlled to optimize the positive effects and minimize the degradation of fermentable sugars.     

Reactive incompatibility of cumene hydroperoxide mixedwith alkaline solutions

Cumene hydroperoxide (CHP) is classified as a flammable hazard in NFPA 43B. Fires or explosions induced by thermal hazards ascribed to the unstable hydroperoxyl or peroxyl groups are often reported. This sequence studies is aimed at the decomposition phenomena associated with the reactive and incompatible characteristics of CHP mixed with alkaline solutions. Various alkalines were used for comparing the relative impact of bases and effects on concentrations. Exothermic onset temperatures and heats of decomposition of these incompatible mixtures were performed by differential scanning calorimetry (DSC). Comparisons of exothermic onset temperature, peak power, heat of decomposition, etc., were assessed to verify the severity of incompatible hazards in these systems. When mixed with a small amount of the hydroxides (in the production or storage of CHP), CHP will be more labile or unstable because of lower exothermic temperature. In addition, to elucidate the final products and propose mechanisms of the reaction of CHP mixed with alkaline solution, the analytical results were carried out by GC/MS and IR. The exhibited reactivity was complicated and significantly affected by the alkaline solutions. The reaction schemes have been proposed in this study. These results are especially important in process safety design for producing CHP and its related compounds, such as phenol, α-cumyl alcohol (CA), acetophenone (AP), and dicumyl peroxide (DCPO).     

Influence of alkaline earth metals on molecular structure of 3-nitrobenzoic acid in comparison with alkali metals effect

The influence of beryllium, magnesium, calcium, strontium and barium cations on the electronic system of 3-nitrobenzoic acid was studied in comparison with studied earlier alkali metal ions [1]. The vibrational FT-IR (in KBr and ATR techniques) and ¹H and ¹³C NMR spectra were recorded for 3-nitrobenzoic acid and its salts. Characteristic shifts in IR and NMR spectra along 3-nitrobenzoates of divalent metal series Mg → Ba were compared with series of univalent metal Li → Cs salts. Good correlations between the wavenumbers of the vibrational bands in the IR spectra for 3-nitrobenzoates and ionic potential, electronegativity, inverse of atomic mass, atomic radius and ionization energy of metals were found for alkaline earth metals as well as for alkali metals. The density functional (DFT) hybrid method B3LYP with two basis sets: 6-311++G** and LANL2DZ were used to calculate optimized geometrical structures of studied compounds. The theoretical wavenumbers and intensities of IR spectra as well as chemical shifts in NMR spectra were obtained. Geometric aromaticity indices, atomic charges, dipole moments and energies were also calculated. The calculated parameters were compared to experimental characteristic of studied compounds.     

Hydrothermal synthesis and crystal structure of two new hydrated alkaline earth metal borates Sr3B6O11(OH)2 and Ba3B6O11(OH)2

Two new hydrated borates Sr(3)B(6)O(11)(OH)(2) (1) and Ba(3)B(6)O(11)(OH)(2) (2) were hydrothermally synthesized. Their structures were determined by single-crystal X-ray diffraction and further characterized by IR, powder XRD, and DSC/TGA. Compound 1 crystallizes in the triclinic space group P-1 with unit cell parameters of a = 6.6275(13) ?, b = 6.6706(13) ?, c = 11.393(2) ?, α = 91.06(3)°, β = 94.50(3)°, and γ = 93.12(3)°, while compound 2 crystallizes in the noncentrosymmetric monoclinic space group Pc with a = 6.958(14) ?, b = 7.024(14) ?, c = 11.346(2) ?, and β = 90.10(3)°. In spite of the differences in symmetry and packing of the borate chains, both structures consist of the same fundamental building block (FBB) of a [B(6)O(11)(OH)(2)](-6) unit and three unique alkaline earth metal atoms.     

On the 1,3-dipolar cycloaddition reactions of indenone with N-N-C dipoles: density functional theory calculations

Density functional theory (DFT) calculations at the B3LYP/6-311G* theoretical level have been performed to study the 1,3-dipolar cycloaddition (1,3-DC) reactions between indenone (1) and different 1,3-dipoles (diazomethane and N-methyl C-methoxy carbonyl nitrilimine, compounds 2 and 3, respectively). The geometrical and energetic properties were analysed for the different reactives, transition states and cycloadducts formed (compounds 4-11). The reactions proceed in the gas-phase by an asynchronous concerted mechanism, yielding different regiochemistry dependent on the 1,3-dipole chosen, although with dipole 3 some degree of synchrony was found in the formation of cycloadduct 5. The 1,3-DC between 1 and 3 was regioselective, being the cycloadduct 11 favoured against 9. The NMR chemical shift parameters (GIAO method) were also calculated for the reactives and cycloadducts.     

Rat osseous plate alkaline phosphatase as Langmuir monolayer--an infrared study at the air-water interface

A glycosylphosphatidylinositol (GPI)-anchored enzyme (rat osseous plate alkaline phosphatase-OAP) was studied as monolayer (pure and mixed with lipids) at the air-water interface. Surface pressure and surface potential-area isotherms showed that the enzyme forms a stable monolayer and exhibits a liquid-expanded state even at surface pressure as high as 30 mN m(-1). Isotherms for mixed dimyristoylphosphatidic acid (DMPA)-OAP monolayer showed the absence of a liquid-expanded/liquid-condensed phase transition as observed for pure DMPA monolayer. In both cases, pure or mixed monolayer, the enzyme preserves its native conformation under compression at the air-water interface as observed from in situ p-polarized light Fourier transform-infrared reflection-absorption spectroscopic (FT-IRRAS) measurements. Changes in orientation and conformation of the enzyme due to the presence or absence of DMPA, as well as due to the surface compression, are discussed.     

Thermal behaviour of organochlorine pesticides in the presence of alkaline substances

Selected organochlorine pesticides, namely lindane, PCNB,p,p′-DDT andp,p′-methoxychlor, and some related compounds (p,p′-DDE andp,p′-DMDE) were heated in the presence of powdered KOH, Na₂CO₃, CaO and CaCO₃ in order to check whether degradation of the compounds is feasible in moderate conditions and temperatures. Thermal analyses, as well as investigations concerning the search for the reaction products revealed that processes occurring at atmospheric pressure are either simple volatilization of organic molecules, observed upon heating of mixtures containing lindane, PCNB,p,p′-DDE andp,p′-DMDE, or volatilization accompanied with decomposition towards HCl andp,p′-DDE andp,p′-DMDE, noted when heating mixtures ofp,p′-DDT andp,p′-methoxychlor with alkaline substances, respectively. Complementary theoretical calculations enabled insight into the mechanism of HCl elimination fromp,p′-DDT andp,p′-methoxychlor.     

Construction of strong alkaline hydrothermal environment for synthesis of copper telluride nanowires

Strong alkaline hydrothermal environment was constructed through adjusting the KOH concentration in solution for the synthesis of Cu_2−xTe nanocrystals. The Cu_2−xTe nanowires were successfully obtained by hydrothermal method without using any template or capping agent. The as-synthesized nanowires were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution TEM (HRTEM). The Cu_2−xTe nanowires with lengths up to hundreds of micrometers have a single crystal hexagonal structure and grow along the [11], [12], [13], [14], [15], [16], [17], [18] , [19] and [20] direction. A growth mechanism was proposed based on the characterization results. The energy gap of as-synthesized Cu_2−xTe nanowires is ca.1.1 eV for direct band transition or 0.7 eV for indirect band transition. The structural phase transformations occur at 322, 353 and 477 °C. And the Cu_2−xTe nanowires exhibit the metal electrical conductivity.     

Advances in alkaline earth-nitrogen chemistry

This article provides a concise summary of alkaline earth metal nitrogen chemistry. This important area of s-block metal chemistry is shedding important light on the recent development of alkaline earth metal chemistry, as the preparation of the target compounds utilizes a large variety of synthetic methodology. Further, the compounds have been utilized in a range of applications, including polymerization initiation, catalysis, as solid-state precursors, and even high energy materials.     

Enzymatic synthesis of phosphoric monoesters with alkaline phosphatase in reverse hydrolysis conditions

Title compounds were synthesized on a preparative scale using alkaline phosphatase, orthophosphoric monoester phosphohydrolase B.C. 3.1.3.1, in reverse hydrolysis conditions. Optimization for one of the 25 phosphoryl acceptors investigated (glycerol) shows that up to 55% synthesis yield can be obtained using a large excess of substrate, conditions in which the enzymatic activity remains high. From the results obtained with different phosphoryl group donors, phosphate, pyrophosphate and polyphosphates and with enzymes of different sources, it comes up that the best results are obtained with pyrophosphate and with the weakly purified calf intestine alkaline phosphatase. The extent of enzymatic hydrolysis of the donor can be reduced owing to the existence of two different pH optima for the two reactions, phosphorylation and hydrolysis. The synthesis can be also performed using inert co-solvents which allow to reduce the amount of acceptor used, as long as Zn⁺⁺ is added to the reaction medium. The results are discussed in terms of the catalytic mechanism of alkaline phosphatase.     

Enhancement of oxygen surface exchange kinetics of SrTiO(3) by alkaline earth metal oxides

The oxygen incorporation reaction in undoped SrTiO(3) was investigated by electrical measurements (pressure modulation technique) in the temperature range from 650-920 degrees C and by means of tracer exchange experiments in the temperature range from 458-600 degrees C. The surface of the undoped SrTiO(3) single crystals was modified by alkaline earth metal compounds leading to a tremendous enhancement of the effective surface exchange rate for oxygen incorporation as compared to the uncoated surface.     

An accurate theoretical study of energy barriers of alkaline hydrolysis of carboxylic esters

Hydrolysis of esters is one of the most important and frequently used reactions in both organic synthesis and biochemistry. While the reaction mechanism in solution is reasonably well understood, many questions still remain to be answered. In the present study, the combination method, MPW1B95/6-311++G(3df,2p)//B3LYP/6-31+G(d)//HF//CPCM/UA0, was found to be reliably predict the energy barriers of alkaline hydrolysis of various esters. The MAD and RMSE were equal to 1.03 and 1.06?kcal/mol, respectively. With this authorized theoretical protocol in hand, we systematically studied the mechanisms of alkaline hydrolysis of ethyl benzoate. The acyl-oxygen cleavage B_AC2 route is preferred over the alkyl-oxygen cleavage B_AL2 route. Then, the total activation energy barriers of B_AC2 and B_AL2 routes of over 40 esters have been calculated. And this large body of data allows us to systematically study the various effects controlling the alkaline ester hydrolysis, including the polar effect, the steric effect, and the remote substituent effect. Also, the solvent effect has been extensively studied in this work. Furthermore, the differences between B_AC2 and B_AL2 routes of these effects are also discussed. The results enable us to predict the energy barrier of the hydrolysis of cyhalofop-butyl in aquatic solution.     

Thermodynamics of double oxides. I. Some aspects of the use of CaF2-type electrolyte for thermodynamic study of compounds based on oxides of alkaline earth metals

The theory of the potentials of the cells with CaF₂-type electrolyte and electrodes based on oxides of alkaline earth metals

$\text{O}{}_2\text{Pt}\text{|〈M}{}_1\text{O}\text{〉|}\text{CaF}{}_2\text{|〈M}{}_{11}\text{O}\text{〉|}\text{Pt, O}{}_2$

is proposed. The limits of utilization of CaF₂ as a function of partial oxygen pressure over electrodes are considered. The conditions of reversibility of the cells are analyzed for obtaining the thermodynamic parameters of the cell reactions under study. The theoretical analysis and experimental results demonstrate the possibilities of using such cells for thermodynamic study of new classes of refractory compounds based on oxides of alkaline earth and rare-earth or transition metals.     

Homoleptic alkaline earth metal bis(trifluoromethanesulfonyl)imide complex compounds obtained from an ionic liquid

The first homoleptic alkaline earth bis(trifluoromethanesulfonyl)imide (Tf2N) complexes [mppyr]2[Ca(Tf2N)4], [mppyr]2[Sr(Tf2N)4], and [mppyr][Ba(Tf2N)3] were crystallized from a solution of the respective alkaline earth bis(trifluoromethanesulfonyl)imide and the ionic liquid [mppyr][Tf2N] (mppyr = 1,1-N-methyl-N-propylpyrrolidinium). In the calcium and strontium compounds, the alkaline earth metal (AE) is coordinated by four bidentately chelating Tf2N ligands to form isolated (distorted) square antiprismatic [AE(Tf2N)4]2- complexes which are separated by N-methyl-N-propylpyrrolidinium cations. In contrast, the barium compound, [mppyr][Ba(Tf2N)3], forms an extended structure. Here the alkaline earth cation is surrounded by six oxygen atoms belonging to three Tf2N- anions which coordinate in a bidentate chelating fashion. Three further oxygen atoms of the same ligands are linking the Ba2+ cations to infinite (infinity)(1)[Ba(Tf2N)3] chains.