Determination of copper by its catalytic effect on the oxidation of hydroquinone by hydrogen peroxide on supports

The reaction of oxidation of hydroquinone by hydrogen peroxide catalyzed by copper(II) in the presence of 2,2’-dipyridyl is activated by hexamethylenediamino groups that are bonded to the surface of filter paper; additional activating effect is produced by 2,2′-dipyridyl. The introduction of malonic acid dinitrile into the indicator reaction improves the sensitivity of the determination of copper and the contrast of the reaction in solution because of the formation of a blue product. Differently colored compounds are formed on a paper support at different concentrations of copper, which makes it possible to visually distinguish the quantities of copper that differ by an order of magnitude in the range 1 × 10^-5-0.5 μg. Quantitative detection is possible in the range 5 × 10^-6-0.1 μg (c_min = 3 × 10^-6 μg). The concentration of copper (0.2-1.5 μg/mL) is determined in blood serum; the consumption of the sample per one determination is 3 μL     

The Effect of the Chain Length on MMA Free Radicl Polymerization

It has been known that the propagation rate coefficient (kp) will change with monomer conversion, Friss, Hamielec et al.1-5 have proposed many formulas about kp to fit this change. In order to obtain the relation between Arrhenius parameters and monomer conversion, a group of kp values at the same monomer conversion must be measured. We adopted a new method through analysis of kp values measured by usual experimental techniques for this purpose. Firstly, we chose a value of monomer convers…     

KINETIC AND APPLICATION: STUDIES ON THE REACTION SYSTEM OF OSMIUM(Ⅳ)-ARSENIC(Ⅲ)-CHLORATE

The experiments have proved that Os(Ⅳ) has very strong catalytic effect on the chlorate oxidation of As(Ⅲ) in perchloric acid media, and As(Ⅲ) exhibits a sensitive single-sweep oscillopolarographic wave at-0.75 V vs. SCE. The kinetics of this catalytic reaction has been investigated by the initial rate procedure. The mechanism has been proposed. A new and highly sensitive catalytic reaction-oscillopolarographic method for the determination of ultratrace amounts of osmium has been described, based on the Os(Ⅳ) catalytic effect on the reaction. The linear range of 5.0×10~(-11)-4.4×10~(-9) mol/L and 6.0×10~(-9)-1.3×10~(-7) mol/L Os was obtained using the fixed-time procedure and the initial rate procedure, respectively. Osmium in refined ore was analysed by this method.     

STUDIES OF UNUSUAL OXIDATION STATES OF TRANSITION METALS (Ⅰ)——KINETICS AND MECHANISM OF OXIDATION OF POTASSIUM THIOCYANATE BY DIPERIODATOARGENTATE(Ⅲ) ION IN ALKALINE MEDIUM

The kinetics of oxidation of potassium thiocyanate by diperiodatoargentate (Ⅲ) (DPA) ions was studied in aqueous alkaline medium ([OH~-]=7.00×10~(-3)—0.200 mol. dm~(-3)) at a constant ionic strength (μ=0.30 mol. dm~(-3)). It is found that the reaction order in DPA is unity. The dependence of the rate on [OH~-] implies that there are two pathways through which the reaction proceeds. In each pathway, the order in NCS-is fractional and the kinetic data fit well in with Michaelis-Menten process. The influence of ligand on the reaction is examined and the reactive species are inferred. Two pathways of inner-sphere two-electrons transfer are believed to be involved in the oxidation. The rate equations are derived and all the equilibrium constants and rate constants are evaluated. Activation parameters of one pathway are determined.     

THEORETICAL STUDY ON THE 1,4-CYCLO-ADDITION REACTION BETWEEN SINGLET OXYGEN (~(1)O_(2)) AND IMIDAZOLE

Quantum chemical ab initio method has been used to study the cycloaddition reaction between singlet oxygen and imidazole theoretically. The intermediate product, an endoper-oxide, of which the structure has not yet been found experimentally was optimized by using energy gradient method. The transition state (TS) structure of this reaction was also located on the potential energy surface and characterized. From the structural features of the TS, e.g. the transition vector of the imaginary vibration mode, as well as the interaction of orbitals, it is realized that this cycloaddition is a synchronous concerted reaction. The activation barriers calculated are 69.5 kJ·mol (forward reaction) and 140.4 kJ·mol-1 (backward reaction) respectively (6-31G results).     

POLYBINAPHTHYLS INCORPORATING (R)-2,2''''-BINAPHTHO-20-CROWN-6 AND NAPHTHYL MOITIES

Chiral polymer was synthesized by the polymerization of (R)-6,6'-bistributylstannyl-2,2'-binaphtho-20-crown-6 (M-1) with 1,4-dibromo-2,3-bisbutoxy-naphthyl (M-2) by Pd(PPh3)4 catalyzed Stille coupling reaction. Both monomer and polymer were analyzed by NMR, MS, FT-IR, UV, polarimetry, DSC-TGA, CD, fluorescent spectroscopy and GPC. The major difference between monomer and polymer is that a long wavelength Cotton Effect was observed for the polymer due to its more extended conjugation in the repeating unit and a highly rigid backbone in the polymer chain. Polymer has strong blue fluorescence due to the efficient energy migration from the extended n-electronic structure of the repeating unit of the polymer to the chiral binaphthyl core and is expected to have potential application in the materials of fluorescent sensors and chiral chromatographic packing for resolution of racemic amino acid.     

PREPARATION AND CHARACTERIZATION OF POLY[STYRENE-co-4-(2-PHENYLTHIOETHYLTHIOMETHYL)STYRENE]

Sulfur-containing monomers have received special interest from researchers because of their outstanding opticalperformance. Using the reaction between 2-phenylthioethyl-1-mercaptan and p-chloromethylstyrene, a new vinyl monomer4-(2-phenylthioethylthiomethyl)styrene (PTETMSt) was synthesized. Its structure was characterized by FT-IR and NMR.Copolymerization of styrene and PTETMSt was investigated. The data show that poly(styrene-co-PTETMSt) has higher refractive index, lower density and percentage of water absorption. The copolymer can be used on optical materials.     

8-羟基喹啉单体及二聚体质子转移反应的理论研究

Density functional theory （DFT） of quantum chemistry method was employed to investigate proton transfer reactions of 8-hydroxyquinoline （8-HQ） monomers and dimers. By studying the potential energy curves of the isomerization, the most possible reaction pathway was found. The total energy of 8-hydroxyquinoline was lower than that of quinolin-8（1H）-one, whereas the order was reversed in dimers. The findings explained the contrary experimental phenomena. The minimum reaction barrier of intramolecular proton transfer was 47.3 kJ/mol while that in dimer was only 25.7 kJ/mol. Hence it is obvious that proton transfer reactions of 8-HQ monomer have a considerable rate but it is easier to proceed for 8-HQ dimer than monomers. It implied that the hydrogen bond played an important role in depressing the activation energy of reaction. The mechanism of the tautomerization was discussed on the basis of theoretical results.     

四氯化钛配合物/甲基锂体系催化降冰片烯开环移位聚合的研究

The ring opening metathesis polymerization of cyclic monomers is relatively a newcomer to the field of polymer chemistry. Depending on the monomer and the catalyst used, this type of reaction yields a wide range of products that have found important industrial applications.     

分子内桥连有机钴配合物的合成及热稳定性研究

The intramolecularly bridged alkyl cobaltic complexes are one of important coenzyme B₁₂ model coplexes. In this paper, study on the thermolytic reaction of aqua(3-bromopropyl)cobaloximes in solution revealed that a new intramolecularly bridged alkyl cobaloximes complex was formed and the reaction is influenced by tempertature and solvent. Adding cyclodxtrin has no obvious effect to the rate of the reaction, but various products with different axial bases were obtained. The intramolecularly bridged alkyl cobaloxime complex (bromo(O-trimethylene-dimethy- lglyoxime)(dimethylglyoximate)cobalt(Ⅲ)) was characterized by EA and ESI-MS. Thermogravimetric analysis of this complex found that a carbon radical that from homolysis of the Co-C bond is retained in the proximity of Co^Ⅱ- complex, which is very similar to the behavior of coenzyme B₁₂.