Determination of titanium by adsorption-voltammetry with 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol (5-Br-PADAP)

Summary The 1:1 complex between titanium (IV) and 5-Br-PADAP can be used to determine titanium by adsorption voltammetry at a stationary Hg-electrode. The experimental conditions for the determination are described. The detection limit is 3×10^–10 mol/l Ti (0.015 ppb). Calibration curves are linear for solutions containing 4×10^–10 to 5×10^–8 mol/l Ti(IV) and an enrichment time of 3 min. The influence of foreign ions was investigated. The determination can be carried out in the presence of a 5000-fold excess of iron.     

Rapid spectrophotometric determination of palladium in titanium alloys with 2-(5-bromo-2-pyridylazo)-5-(diethylamino)phenol

A rapid spectrophotometric method for the determination of Pd in titanium alloys is proposed. It is based on the reaction of 2-(5-bromo-2-pyridylazo)-5-(diethylamino)phenol with Pd(II) in a sulphuric acid medium in the presence of ethanol. Beer's law is obeyed up to 40 mug of Pd. The molar absorptivity is 4.5 x 10(4) 1.mole(-1).cm(-1). The standard deviation is 0.3 mug of Pd and the coefficient of variation varies from 0.8 to 3.3%. The elements ordinarily present in such alloys do not interfere. High selectivity is achieved by using fluoroboric acid as masking agent. Improvements in the method of sample decomposition also contribute to the rapidity of the method.     

Crystal and molecular structures of isomeric 2-morpholino-2-thiono-4-methyl-1,3,2-dioxaphosphinane and 2-morpholino-2-oxo-4-methyl-1,3,2-dioxaphosphinane

Two isomeric pairs of compounds, cis- and trans-2-morpholino-2-thiono-4-methyl-1,3,2-dioxaphosphinane ( 1A + 1B ) and 2-morpholino-2-oxo-4-methyl-1,3,2-dioxaphosphinane ( 2A + 2B ) were obtained and separated into the pure compounds by silica gel chromatography. Attempts at crystallization afforded 1A , 1B , and 2B . Each crystalline isomer was studied by the X-ray technique, and each crystal and molecular structures assigned. These studies revealed that 1B and 2B have exocyclic 4-CH₃ and sulfur (for 1B ) or 4-CH₃ and oxygen (for 2B ) in the diequatorial position (cis-geometry), while compound 1A possesses the 4-CH₃ group in equatorial position while sulfur is in an axial position (trans-geometry). For all the examined compounds, all the basic geometrical parameters, such as bond lengths, bond and torsion angles, and the deformation of a chair conformation of the six-membered heterocyclic rings, have been established. Such unambiguous assignment of cis-trans geometry in both pairs of 1 and 2 allowed us to confirm the stereoretentive PS → PO conversion by means of OXONE® and the stereoinvertive mechanism of formic-acid catalyzed hydrolysis of phosphorothiomorpholidates. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:271–279, 1998     

Synthesis of Bis(2-benzofuranyl) Diselenides from 4-(2-Hydroxyaryl)-1,2,3-selenadiazoles

4-(2-Hydroxyaryl)-1,2,3-selenadiazoles obtained by the action of selenium(IV) oxide on o-hydroxyacetophenone semicarbazones are readily converted into the corresponding potassium benzofuran- 2-selenolates via reaction with potassium carbonate. Oxidation of potassium benzofuran-2-selenolates with iodine gives bis(2-benzofuranyl) diselenides in good yields.     

Synthesis and Crystal Structure of Cis 2-（6-Chloro-3-pyridylmethylamino）-4-chlorophenyl- 5,5-dimethyl- 1,3,2-dioxaphosphinane 2-Oxides

1 INTRODUCTION Neonicotinioid insecticides as nicotinic acetyl-choline receptor inhibitors have attracted increasingattention because of its safety, low toxicity, wide andhigh activities[1, . A lot of new insecticides such as 2]imidacloprid, acetamiprd and nitenpyram have beencommercialized. It is found that most biologicallyactive nicotinic compounds contain 3-aminomethyl-pyridine moiety[3]. Due to their wide biological acti-vities, organic phosphorus heterocyclic compoundsplay an import…     

Synthesis of 2-(1,2,3-Thiadiazol-5-yl)-1H-benzimidazoles

We have developed a convenient preparative method for synthesis of previously unknown 2-(1,2,3-thiadiazol-5-yl)-1H-benzimidazoles based on reaction of benzoylhydrazones of 2-acylmethyl-1H-benzimidazoles with thionyl chloride. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1391–1393, September, 2005.     

Synthesis of some 4-substituted-2-(o-halogenophenyl)-1,2,3-triazoles

Mesoaldehyde 1,3-dioxime was treated with either 2,4,6-trichlorophenyl- (a), o-fluorophenyl- (b), or o-bromophenyl- (c) hydrazine to give the corresponding mesoaldehyde 1,3-dioxime-2-halogenophenylhydrazones (1a,b,c). The latter were O-acetylated with acetic anhydride, and cyclized to triazole 4-oximes (3b, c) or triazole 4-O-acetyloximes ( 6a,b,c ) with cesium carbonate, then converted to nitriles ( 7a,b,c ) by refluxing with acetic anhydride followed by pyrolysis, or to aldehydes ( 4a,b,c ) by hydrolysis. The nitriles ( 7a,b,c ) were also converted to acids ( 9a,b,c ), esters ( 10a,b,c ), amides ( 8a,c ), an alcohol (11a), and an amine ( 12a ). In addition, tetrazoles of two types were prepared. The first ( 13d,e ) were obtained from the acid chlorides by the action of 5-aminotetrazole, whereas the second ( 14f ) was produced from the respective nitrile by the action of ammonium azide.     

(Organylsulfanyl)chloroacetylenes: VIII. Reaction with (diethylamino)trimethylsilane

(Alkylsulfanyl)chloroacetylenes react with (diethylamino)trimethylsilane in diethyl ether (20–22°C) to form dialkyl(alkylsulfanylethynyl)amines (19–29%) and 1,3-bis(alkylsulfanyl)-4-chloro-4-(diethylamino)but-3-en-1-ynes (17–42%). The yield depends on the reagent ratio.     

Selenium heterocycles. XXXVII . Synthesis of 4-(thiazol-4-yl)-1,2,3-selenadiazoles and 4-(selenazol-4-yl)-1,2,3-selenadiazoles

Starting from readily available 2-substituted-4-formylthiazoles and selenazoles, a series of 4-(2-aryl-4-selenazolyl)-1,2,3-selenadiazoles I and 4-(2-substituted-4-thiazolyl)-1,2,3-selenadiazoles II were prepared. Pyrolysis of compound II afforded (2-substituted-4-thiazolyl) acetylenes VII. Addition of potassium hydroxide pellets to an alcoholic solution of II gave 2-substituted-1,4-diselenafulvenes VIII. Decomposition of compound II with base followed by the addition of carbon disulfide gave 5-substituted 2-thioxo-1,3-thiaselenoles XI.     

Synthesis of 4-(diethylamino)-3-methylbutan-2-ol under conditions of phase-transfer catalysis

Russian Journal of Organic Chemistry -     

4-(2-Hydroxyaryl)-1,2,3-selenadiazoles as Precursors of Benzofuran-2-selenolates

The reaction of selenium dioxide with o-hydroxyacetophenone semicarbazones gives 4-(2-hydroxyaryl)-1,2,3-selenadiazoles which undergo ready decomposition by the action of potassium carbonate to form benzofuran-2-selenolates. The latter can be alkylated with methyl iodide and benzyl chloride and arylated with 2,4-dinitrochlorobenzene. Intermediate formation of 2-(o-hydroxyphenyl)ethyneselenolate during decomposition of 1,2,3-selenadiazoles was proved by the isolation of methyl o-methoxyphenylethynyl selenide when the substrate was treated with potassium carbonate in the presence of methyl iodide.     

4-(2-Hydroxyaryl)-1,2,3-thiadiazoles as a Source of 2-Benzofuranthiolates

Following the Hurd-Mori procedure, 4-(2-hydroxyaryl)-1,2,3-thiadiazoles were synthesized from o-hydroxyacetophenones. Treatment of the products with bases gives 2-benzofuranthiolates which can be involved in alkylation and arylation reactions.     

Reactions of 3-(Polyfluoroalkyl)propane-1,2,3-trione-2-oximes with Diaminoarenes

Novel quinoxaline derivatives have been synthesized via the reaction of 3-trifhioromethyl-1,2,3-propanetrione-2-oximes with 1,2-diaminobenzene or 2,3-diaminonaphthalene: 2-trifluoromethyl-3-aroylquinoxaline and 2-trifluoromethyl-3-aroylbenzo[g]quinoxaline. Under similar conditions, 3-R^F-1,2,3-propanetrione-2-oximes [R^F = C₃F₇, H(CF₂)₄, C₄F₉, and C₆F₁₃] with the same diaminoarenes have given a mixture of the condensation and fragmentation products in different ratios. The structure of (4-methylphenyl)[3-(tri-fluoromethyl)benzo[g]quinoxalin-2-yl]methanone has been elucidated by means of X-ray diffraction analysis.

     

Preparation and characterization of chelating resins loaded with 2-(5-bromo-2-pyridylazo)-5-(diethylamino)phenol for preconcentration of rare earth elements

 Chelating resins prepared by sorption of 2-(5-bromo-2-pyridylazo)-5-(diethylamino)phenol (5-BrPADAP) on macroporous resins (Amberlite XAD-4 and XAD-7) were characterized. The adsorption properties (amount of chelating agent adsorbed per gram of resin, sorption kinetics, retention capacity, etc.) and the thermodynamic quantities of each adsorption process were determined. The retention of some rare earth elements (e.g. Er, Yb and Lu) on these chelating resins was studied in order to preconcentrate them for their determination by X-Ray fluorescence spectrometry. Received: 7 September 1995/Revised: 2 January 1996/Accepted: 10 January 1996