Triazoles and Fused Triazoles II: Synthesis of Certain Substituted s-Triazoles,s-Triazolo[3,4-b]-1,3,4-Thiadiazoles and s-Triazolo [3,4-b]-1, 3,4-Thiadiazines

The synthesis of a certain series of s-triazoles and fused s-triazoles namely: 3-(3,4-dimethoxyphenyl)-4-arylideneamino-5-mercapto-s-triazoles 3.8 , 3-(3,4-dimethoxyphenyl)-6-substituted-s-triazolo[3,4-b]-1,3,4-thiadiazoles 11-17 , 3-(3,4-dimethoxyphenyl)-6-substituted thio-s-triazolo[3,4-b]-1,3,4-thiadiazoles 19, 20 and 3-(3,4-dimethoxyphenyl)-6-substituted-7H-s-triazolo[3,4-b]-1,3,4-thiadiazines 21, 22 , is described.     

Medium effects on the initial and the transition states upon the solvolysis of trans‐dichlorobis(N‐methyl‐ethylenediamine)cobalt(III) complex in water‐mixed solvents

The kinetics of solvolysis of trans‐dichlorobis(N‐methylethylenediamine)cobalt(III) complex have been investigated in aqua‐organic solvent media (0–60% (v/v) cosolvent) at 25 ≤ t°C ≤ 60, using n‐propanol and tert‐butyl alcohol as cosolvents. The first‐order rate constant increased nonlinearly with the reciprocal of the dielectric constant D_s^?1, and x_org, reflecting the individuality of the cosolvents and thereby suggesting that the relative stabilities of the transition state and initial state were governed by the preferential solvation effect. The thermodynamic parameters (ΔH^≠ and ΔS^≠) were sensitive to the structural changes in the bulk solvent phase. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 495–499, 2002     

Pseudoheterogeneous polymerization of methyl methacrylate initiated by sodium bisulfite in presence of glassy powder of PbO?SiO2

The aqueous polymerization of methyl methacrylate with sodium bisulfite as initiator was catalyzed by PbO? SiO₂, PbO (70 mole %)? SiO₂ (30 mole %) with a particle size < 200 mesh had the highest catalytic effect. The average molecular weight obtained in the presence of amorphous PbO? SiO₂ glass was higher than that obtained in the presence of crystalline PbO—SiO₂ glass powder. In this system mild shaking increased the rate of polymerization. Silicon dioxide catalyzed the rate of polymerization to a higher extent than PbO, which had a slightly higher catalytic effect than lead silicate powder. The average molecular weight formed in the presence of PbO was higher than that formed in the presence of lead silicate, which in turn was higher than that formed in the presence of silicon dioxide. Increasing the initiator concentration decreased the average molecular weight. Mild shaking decreased the average molecular weight obtained when polymerization was carried out in air but increased it in a nitrogen atmosphere. Methanol decreased the conversion percentage of monomer to polymer and the average molecular weight due to its transfer reaction.     

Chelation of somebisazophenyl-β-diketone derivatives with lanthanide metal ions

Summary The chelation behaviour ofbisazo--diketone compounds with La, Ce, Nd, Sm, Gd, Er, and Lu ions was investigated. Composition and stability constants of the chelates have been determined by conductometric and potentiometric techniques. Electronic absorption, IR, and¹H NMR spectra as well as molar conductance and elemental and thermal analyses were used to characterize the complexes.

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Komplexierung einiger Lanthaniden mitBisazophenyl--diketon-Derivaten

Zusammenfassung Das Komplexierungsverhalten einigerBisazophenyl--diketone mit La, Ce, Nd, Sm, Gd, Er und Lu wurde untersucht. Zusammensetzung und Stabilitätskonstanten der Chelate wurden mit konduktometrischen und potentiometrischen Methoden bestimmt. Zur Charakterisierung der Komplexe wurden UV/Vis-, IR- und¹H-NMR-Spektroskopie sowie molare Leitfähigkeit, Elementaranalyse und thermische Analyse herangezogen.

     

Omega chrome green BLL: A new analytical reagent

Summary Omega Chrome Green BLL was used as a metal indicator for the direct complexometric titration of copper, lead, thorium and for the back titration of aluminium using thorium as a back titrant. It was also used as a colorimetric reagent for the microdetermination of copper and vanadium. A large number of anions and cations do not interfere in such a determination even if they are present in 10 folds the amount of copper or vanadium. Interference due to ferric iron is simply eliminated by the addition of few crystals of ascorbic acid to reduce it to the ferrous state.     

Validated UPLC method for the determination of guaiphenesin,oxeladin citrate,diphenhydramine, and sodium benzoate in their quaternary mixture used in treatment of cough,in the presence of guaiphenesin-related substance (guaiacol)

Accurate, precise, and sensitive UPLC method was developed and validated for the simultaneous determination of a quaternary mixture containing guaiphenesin (GUP), oxeladin citrate (OXC), diphenhydramine (DPH), and sodium benzoate (SOB) in the presence of GUP-related substance, guaiacol (GUA). Chromatographic separation was achieved using NUCLEOSHELL^® column—C₁₈ (4.0?×?50.0 mm, 2.7 μm). Isocratic elution at a flow rate 1.0 mL/min was performed using a mobile phase consisting of acetonitrile:phosphate buffer pH 3.5?±?0.1 (25.0:75.0, v/v). The specificity of the developed method was investigated by analyzing of laboratory-prepared mixtures containing different ratios of the four drugs, in the presence of GUA as well as their combined pharmaceutical formulation. The obtained results were statistically compared with those obtained by the official or reported methods, showing no significant difference with respect to accuracy and precision at p?=?0.05.     

The Reaction of Cyclohexan-1,3-dione with Cyanomethylenes: Synthesis of Thiophenes and Their Fused Derivatives with Antifungal Activities

Abstract

2-Amino-7-oxotetrahydrobenzo[b]thiophenes 3a,b were prepared according to the Gewald procedure. Their reactivity toward a variety of chemical reagents was studied to give annulated heterocycles with potential bio-responses.     

Electrochemical Behaviour of Iron in a Third‐Generation Ionic Liquid: Cyclic Voltammetry and Micromachining Investigations

The electrochemical behaviour of Fe in 1‐ethyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide ([Emim]⁺Ntf2^?) and mixtures with Cl^? is studied with the aim of investigating the applicability of ionic liquids (IL) for the electrochemical machining of iron. Whereas in pure IL iron could not be significantly dissolved, the addition of Cl^? enables the active dissolution with anodic current densities up to several mA cm^?2. Although several anodic peaks appear in the cyclic voltammograms (CV), the distinct assignment of those electrochemical processes remain difficult. In particular no proof for the formation of FeCl_x^2?x complexes during Fe dissolution are deduced from the CV, although such complexes are shown to be stable in the employed electrolyte. In addition, we present electrochemical drilling experiments with short potential pulses, which demonstrate that electrochemical machining of Fe is, in principle, possible in IL based electrolytes, even though hampered by slow machining speed.     

Ytterbium triflate catalyzed synthesis of alkoxy-substituted donor-acceptor cyclobutanes and their formal [4 + 2] cycloaddition with imines: stereoselective synthesis of piperidines

A new synthesis of 2-alkoxy-1,1-cyclobutane diesters and their first use in dipolar cycloadditions is reported. Both the formation of the donor-acceptor cyclobutanes and their subsequent annulation with in situ formed imines are catalyzed by Yb(OTf)(3). Cyclobutanes with carbon donor groups give piperidines with high trans stereoselectivity.