Anhydrous lead(II) heptanoate

The title compound, catena‐poly­[[(heptanoato‐O,O′)­lead(II)]‐μ‐heptanoato‐O,O′:O:O′], [Pb(C₇H₁₃O₂)₂], is a metallic soap which can be used as a corrosion inhibitor since it forms a passive film at the Pb surface. Its structure is characterized by two‐dimensional layers parallel to the bc plane. The layers are packed through van der Waals interactions along the a direction and form blocks parallel to (001). The 6s² lone pair of electrons on Pb^II is stereochemically active in this compound, which leads to a hemidirected octahedral geometry for the O‐environment around the Pb atoms.     

Two-dimensional Anhydrous Cadmium(II) Phthalate

The in situ hydrolysis of phthalyl-γ-glutaminyl-histidine with Cd(ClO₄)₂·6H₂O in the presence of water and methanol affords a novel two-dimensional cadmium coordination polymer, a new phase, anhydrous cadmium(II) phthalate, ( 1 ). The structure was determined by single crystal X-ray diffraction. Crystal data: P2₁/c, a = 13.8168(14), b = 7.0351(7), c = 8.2054(8) Å, β = 105.540(2)°, V = 768.43(13) ų, Z = 4, R₁ = 0.0380, wR₂ = 0.1111.     

Anhydrous polymeric zinc(II) octanoate

The structure of the title compound, poly­[zinc(II)‐bis(μ‐octanoato‐O:O′)], [Zn(C₈H₁₅O₂)₂]_n, consists of polymeric sheets parallel to (100) in which tetrahedrally coordinated Zn²⁺ cations are connected by carboxyl­ate bridges in a syn–anti arrangement.     

Anhydrous tin and lead hexacyanoferrates (II). Part II. Electronic structure and chemical bonding

The electronic structure and chemical bonding of anhydrous tin and lead hexacyanoferrates (II) have been studied using the linear muffin-tin orbital method in the tight-binding minimal basis set approximation and semi-empirical Hückel method. The hybridised s- and p-states of CN-groups were shown to have a dominant influence on the electronic structure of these compounds, that results in strong splitting of iron d-states. The chemical bonding C–N and Fe–C in the [Fe(CN)₆]^4–-complex are mainly covalent. Bonds between Pb(Sn) and N atoms are more weak covalent and anisotropic. The low stability of tin hexacyanoferrate is due to high anisotropy of Sn–N bonding.     

Initial Mass Loss in Anhydrous Manganese(II) Pyrrolidinedithiocarbamate. Decomposition or sublimation

Investigation on the nature of an initial mass loss observed for Mn(II)pyrrolidinedithiocarbamate complex is described. No evidences of decomposition are observed in infrared or mass spectra, elemental analysis and scanning electron microscopy of the residue at the end of the first thermal event, when compared with the same data for the original complex. Partial sublimation is assigned as the physical event after several experiments. The results are comparable with the findings for other complexes of the first transition series with pirrolidinedithiocarbamate. This revised version was published online in July 2006 with corrections to the Cover Date.     

微波辐射下可可碱的N-烃基化

在微波辐射下以无水碳酸钾作为碱性试剂和载体,可可碱和卤代烃在固相能迅速发生反应生成相应的N－烃基化产物。     

Anhydrous tin and lead hexacyanoferrates (II).: Part I. Synthesis and crystal structure.

The crystal structure of Pb₂Fe(CN)₆ and Sn₂Fe(CN)₆ has been first determined and refined using the Rietveld method with combined CuKα₁ X-ray and constant-wavelength neutron powder diffraction data in space group P-3 (147, Z=1). The unit cell constants are a=7.1346(1) and 7.1805(1) Å, c=5.4531(2) and 5.3639(1) Å, respectively. The compounds are layered, groups of three nearest [Fe(CN)₆]⁴⁻-complexes are joined to layers by means of Pb or Sn atoms. The same Pb or Sn atoms (c.n.=3+3) joint three nearest complexes from the next layer. The jointing goes through ‘nitrogenlead(tin)nitrogen’ bonds.     

Anhydrous tetrabutylammonium fluoride

Tetrabutylammonium fluoride (TBAF) is prepared at low temperature by nucleophilic aromatic substitution of hexafluorobenzene with tetrabutylammonium cyanide. Adventitious water is scavenged during this synthesis by the generated hexacyanobenzene, which readily adds water under basic conditions. Contrary to expectations, TBAF is stable to Hofmann elimination in polar aprotic solvents under anhydrous conditions. Added hydroxylic solvents are shown to catalyze the decomposition of TBAF and to catalyze proton exchange with DMSO. The synthetic utility of this salt is described briefly.     

Peculiarities of Chemical Binding in Anhydrous Lead(II) and Tin(II) Hexacyanoferrates(II,III)

The electronic structure and chemical binding of anhydrous lead and tin hexacyanoferrates(II,III) Pb₂Fe(CN)₆, Pb_1.5Fe(CN)₆, and Sn₂Fe(CN)₆ were studied by the linear muffm-tin orbital (tight binding approximation) and extended Hückel theory methods. The general tendencies of variation for the stability of the Pb–N, Sn–N, Fe–C, and C–N bonds were determined for Pb₂Fe(CN)₆, Pb_1.5Fe(CN)₆, and Sn₂Fe(CN)₆ crystals. Peculiarities of Pb(Sn)–N chemical interactions in the structure of the phases have been found.     

ChemInform Abstract: Anhydrous Tin and Lead Hexacyanoferrates(II). Part 2. Electronic Structure and Chemical Bonding

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Thermosynthesis of Anhydrous Phosphates

Abstract

Thermosynthesis is a direct and, in the majority of cases, a shorter way of obtaining anhydrous phosphates. In the present paper oxides (carbonates) of multivalent metals and ammonium dihydrogen phosphate were used as initial components. However, the complicated and incessantly changing composition of decomposition products of ammonium dihydrogen phosphate in a wide temperature range virtually excludes the possibility to investigate the systems under equilibrium conditions (in some cases one can investigate only metastable state systems, in which the “equilibrium” is reached “from below”). With the aim, regardless of the above-mentioned, to retain the opportunity to summarize all basic chemical processes (leading reactions) of solid-phase interaction of the initial components we have made use of complex schemes of solid-phase reactions under dynamic (nonequilibrium) conditions with different phosphorus-metal ratios and temperature rate. It does not exclude application of state diagrams (in more narrow composition ranges or at higher temperatures) when possible. Such complex approach enhances the probability of forecasting compounds and development of optimum synthesis course. Solid-phase reactions of obtaining condesated phosphates by the method of heating oxides (carbonates) of metals with ammonium dihydrogen phosphate were studied for such multivalent metals as magnium, calcium, zinc, copper, cadmium, manganese, cobalt, nickel, scandium, titanium, vanadium, chromium, cerium.     

可可碱与牛血清白蛋白作用光谱特性的研究

本文应用荧光光谱法研究了可可碱（TB）与牛血清白蛋白（BSA）相互作用的光谱特性。测定了18℃、30℃、40℃温度下的结合常数KA分别为1．68×10^4、1．58×10^4、1．45×10^4L／mol,结合位点数咒分别为1．04、1．03、1．03。实验结果表明：TB对BSA内源荧光的猝灭机理主要为静态猝灭;热力学参数探讨其相互作用机理,TB主要以静电力与BSA相互作用;研究了TB对BSA构象的影响,BSA的荧光主要源于色氨酸残基。同时研究了Cu^2＋存在下TB与BSA的相互作用。     

The HPLC Analysis of Caffeine and Theobromine in Animal Diets

Abstract

An HPLC method is described for the analysis of added caffeine and theobromine in animal diets using HPLC with samples extracted in CHC1₃ and interferences eliminated with a Sep-pak^tm. This method has good accuracy and precision but is not suitable for matrixes where the methylxanthines exist as a integral part of the matrix (e.g., foods).     

Comparison of Adsorption Isotherms of Methylxanthines on C18 Column

A comparison of the adsorption isotherms of caffeine, theophylline and theobromine and the competitive adsorption of the three compounds on a C 18 column were investigated. The experimental parameters of the equilibrium isotherms were estimated by linear and nonlinear regression analyses. The linear equation as a function of the adsorption concentration of the single compound in its solution and the competitive adsorption of a single compound in a mixed solution were then determined. The adsorption equilibrium data were then correlated to the linear, Langmuir, Freundlich, Langmuir-Freundlich and stoichiometric displacement theory for adsorption(SDT-A) isotherm models. The mixed compounds of the three compounds were competitively adsorbed on the C 18 particles. The expression of stoichiometric displacement theory for adsorption was found to be more suitable for adsorption of methylxanthines on a C 18 column.     

Chemoselective Synthesis of 1,1-Diacetates from Aldehydes Using Anhydrous Cobalt(II) Bromide Under Solvent-Free Conditions

A mild and efficient method has been developed for the chemoselective preparation of 1,1-diacetates (acylals) from aldehydes catalyzed in the presence of a catalytic amount (0.1 mmol) of anhydrous cobalt(II) bromide under solvent-free conditions. The remarkable selectivity under mild and neutral conditions, excellent yields, short reaction time, and easily available and inexpensive catalyst are important features of this method.