Polarographic behaviour of 1,3-bis[(2-pyridyl)methyleneamino]thiourea (PMAT) in absence and presence of Triton X-100

The polarographic behaviour of 1,3-bis[(2-pyridyl)methyleneamino]thiourea (PMAT) in solutions of varyingpH has been studied both in the absence and presence of Triton X-100 (T.X-100). The mechanism for the reduction process is discussed. The adsorption effect of electrochemically inactive T.X-100 on the polarographic waves ofPMAT has been investigated. The values of the kinetic parameters for the electrode reaction at differentpH values have been computed. The applicability of the polarographic method for determination ofPMAT is also discussed.

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Das polarographische Verhalten von 1,3-Bis[(2-pyridyl)methylenamino]-thioharnstoff (PMAT) in Anwesenheit und Abwesenheit von Triton X-100. Die polarographische Bestimmung vonPMAT

Zusammenfassung Es wurde das polarographische Verhalten vonPMAT in Lösungen mit verschiedenempH sowohl in Gegenwart als auch ohne Triton X-100 (T.X-100) untersucht. Es wird ein Mechanismus für den Reduktionsprozeß diskutiert. Der Adsorptionseffekt des elektrochemisch inaktiven T.X-100 wurde hinsichtlich der polarographischen Wellen vonPMAT untersucht. Die kinetischen Parameter der Elektrodenreaktion wurden für verschiedenepH-Werte ermittelt. Ebenso wird die Anwendbarkeit der polarographischen Methode für die Bestimmung vonPMAT diskutiert.

     

Single‐electron‐transfer/degenerative‐chain‐transfer mediated living radical polymerization of vinyl chloride catalyzed by thiourea dioxide/octyl viologen in water/tetrahydrofuran at 25 °C

The single‐electron‐transfer/degenerative‐chain‐transfer mediated living radical polymerization (SET–DTLRP) of vinyl chloride (VC) in H₂O/tetrahydrofuran at 25 °C catalyzed by thiourea dioxide [(NH₂)₂C?SO₂] is reported. This polymerization occurs only in the presence of a basic sodium bicarbonate (NaHCO₃) buffer and the electron‐transfer cocatalyst octyl viologen. The resulting poly(vinyl chloride) (PVC) has a number‐average molecular weight of 1500–7000 and a weight‐average molecular weight/number‐average molecular weight ratio of 1.5. This PVC does not contain detectable amounts of structural defects and has both active chloroiodomethyl and inactive chloromethyl chain ends. Because of possible side reactions caused by the primary sulfoxylate anion (SO), the catalytic activity of (NH₂)₂C?SO₂ in the SET–DTLRP of VC is lower than that of the single‐electron‐transfer agent sodium dithionite. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 287–295, 2005     

Optimization of alkali-alkalkine earth cation separation on weak cation-exchangers

Summary The elution behavior of alkali and earth alkaline cations has been studied on a newly synthesized weak cationexchanger (WCX). Applying this stationary phase isocratic separation of these cations is possible. The dependence of retention on competing ion concentration is described via a simple model. The influence of crown ethers as well as organic eluent additives on selectivity and peak efficiency is demonstrated. With optimized separation such cations can be determined with detection limits of about 0.5 ppm using a conductivity detector without ion suppression.     

碱土金属掺杂纳米TiO2催化剂的制备与光催化活性的评价

The nanometer TiO₂ were prepared by the hydrolyze-gel method and fellowed by doping alkaline-earth metals (Mg, Ca, Sr, Ba). XRD, SEM, diffuse reflection spectra were used to investigate their characteristices. The result indicates that the average particles size of the TiO₂ is about 80 nm and keep uniformity in distributing. The product was mainly anatase in 300～400 ℃ calcinations, the einstein shift of absorption spectrum was observed after doping the alkaline-earth metals. The best mole percentages of Mg, Ca, Sr and Ba are 0.5%, 1.0%, 1.5%, 1.5% respectively. Under the same reaction conditions, it is more effective to the UV-catalyed degradation reaction that the catalysts containing Mg and Ca were calcined at 300 ℃ for 1h or containing Sr and Ba were calcined at 400 ℃ for 1 h. The photocatalystic activity is considerably depondent on pH and the concentration of the oxidant. Using the sunlight to do the degradation experimental, the result also show that the doping catalysts has higher degradation efficiency than that of pure TiO₂.     

Complex formation equilibria between Ag(I) and thioureas in n-propanol

Complex formation equilibria between Ag(I) and thiourea or N-alkyl-substituted thioureas have been investigated in n-propanol by potentiometry at 10 °C intervals from 5 to 50 °C. Stepwise formation of tris-coordinated AgL_n (n = 1-3) complexes has been found for the majority of the ligands. ΔH and ΔS values for the complex formation reactions have been evaluated from the dependence of ln β_n on temperature. The alkyl-substituents affect the ligand affinities in different ways in relation with the coordination level n.The reactions are exothermic with few exceptions. Enthalpy favoured complex formation with negative dependence of ΔG on temperature (ΔS > 0) have been found.The enthalpy and entropy changes for the stepwise complex formation equilibria are correlated by two linear compensative relationships with the same isoequilibrium temperature 50-51 °C.     

Reaction of benzothiazol-2-one with 4-hydroxy-4-methyl-2-pentynonitrile

Reaction between the title compounds gave the unexpected 3-[5,5-dimethyl-2,5-dihydrofur-4-yl-2-(3-isopropanol-2-propenonitrile)imino]benzothiazol-2-one, as a result of the addition of two cyanoacetylene molecules.Irkutsk Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences, Irkutsk 664033. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 4, pp. 1003–1005, April, 1992.     

Thioureas from 3-aminoquinazolin-4(3H)-one. 2. Unusual alkaline recyclization of 3-(N",N",S-trialkylisothioureido)quinazolin-4(3H)-ones into new 1,3,4-oxadiazoles

3-(N",N",S-trialkylisothioureido)quinazolin-4(3H)-ones obtained by the reactions of 3-(N",N"-dialkylthioureido)quinazolin-4(3H)-ones with alkyl halides undergo unusual recyclization into 5-(2-aminophenyl)-2-dialkylamino-1,3,4-oxadiazoles under the action of aqueous solutions of alkali, hydrazine, and primary aliphatic amines. A plausible mechanism of the recyclization was proposed.     

Study of the Influence of Alkaline Ions (Li, Na and K) on the Structure of the Silicate Entities in Silico Alkaline Sol and on the Formation of the Silico-Calco-Alkaline Gel

The study of silico-calco-alkaline gel is essential to warn against the degradation of concrete due to the alkali-silica reaction. In the laboratory, those gels are simulated by the destabilization of a silico-alkaline sol by calcium ions. Their speed of formation depends on the alkali species. The influence of alkaline ions (Li, Na and K) on the structure of silicate entities in sol and on the gel formation has been studied. The state of polymerization of the silico-alkaline sol was determined by NMR and depends on the alkali species and the molar ratio (Rm = [SiO2]/[A2O] with A = Li, Na or K). It appears that lithium enhances the polymerization. By scattering techniques (SAXS and ELS), the evolution of size and number of scattering particles during gelation can be determined from scattering curves with Guinier approximation. The mechanism of gelation appears as a hierarchic structure composed of several discrete sizes.     

Double bond isomerization of 5-vinylbicyclo[2.2.1]hept-2-ene to 5-ethylidenebicyclo[2.2.1]hept-2-ene over alkaline earth oxides

All the alkaline earth oxides exhibit activities for double, bond isomerization of 5-vinylbicyclo[2.2.1]hept-2-ene (VBH) to 5-ethylidenebicyclo[2.2.1]hept-2-ene (EBH) at a reaction temperature of 273 K. The order of the activity on the basis of unit weight of catalyst was CaO>MgO>SrO>BaO when compared under optimum pretreatment conditions. The E/Z ratio in the products is determined by the reaction temperature regardless of the type of catalyst; the ratios were 82/18 and 88/12 for the reaction temperatures of 323 and 273 K, respectively.     

Na2SiO3对碱性硫脲溶液选择性溶金的影响

采用电化学方法研究Na2SiO3浓度对碱性硫脲浸金的影响和金及其常见伴生元素银、铜、镍、铁在含有Na2SiO3的碱性硫脲溶液中的电化学行为.研究结果表明:加入Na2SiO3在很大程度上提高了金的溶解电流,Na2SiO3的最佳浓度为0.15mol/L.分析不同电势时lgJ与lgc(Na2SiO3)之间的关系可得:在电势为0.42V时,Na2SiO3对碱性硫脲溶液电化学溶金的促进作用最显著,含Na2SiO3的碱性硫脲溶液对金的溶解具有一定的选择性;在电势为0.58V时溶金效果最佳,金、银、镍和铁的阳极电流密度分别为2.49,1.22,1.03和0.09mA/cm2;而同时加入Na2SiO3和Na2SO3时碱性硫脲溶液选择性溶金的最佳电势负移至0.42V,对金的选择性溶解更为明显,金、银、铜、镍和铁的溶解电流密度依次为3.83,1.13,0.73,0.14和0.09mA/cm2,金的溶解电流密度分别是银、铜、镍和铁的3.4,5.2,27.3和42.6倍.