Determination of explosive vapor concentrations with remote sampling in the control of objects

A procedure is proposed for the determination of the vapor concentration of 2,4,6-trinitrotoluene (TNT) in air at a level of 10^–16 g/cm³ in the control of objects for the presence of TNT. The procedure includes preconcentration of TNT vapors and gas chromatographic determination with a limit of TNT detection at a level of 0.08 ± 0.02 pg in a sample. The procedure was applied to the control objects in cells of typical automatic luggage locker with sampling through sampling air ducts. A measure of sample losses as the breakthrough of vapors through sampling air ducts and gas dynamic conditions for the reduction of vapor losses as the ratio of diffusion coefficient to the air duct flow rate were proposed. The time constant of the saturation of the sampling system with TNT vapors and the time constant of its cleaning were determined. It was shown that TNT vapors can be detected virtually satisfactorily near TNT-containing objects with sampling through long channels.     

Primary photophysical and photochemical processes for Pt(SCN)<Subscript>6</Subscript><Superscript>2–</Superscript> complex

Photosolvation of a Pt^IV hexathiocyanate complex Pt(SCN)₆ ^2– in water and ethanol was studied by steady-state photolysis, nanosecond laser flash photolysis, and ultrafast kinetic spectroscopy. Complexes Pt(SCN)₅(H₂O)^– and Pt(SCN)₅(C₂H₅OH)^– were found to be the only reaction products. The quantum yields of photosolvation are independent of the excitation wavelength, being equal to 0.25 and 0.5 for the solutions of the complex in water and ethanol, respectively. Photosolvation proceeds by the mechanism of heterolytic metal—ligand bond dissociation without involvement of redox processes. The characteristic time of formation of the end products for both solvents is about 10 ps. Three successive intermediates detected on the picosecond time scale were interpreted as Pt^IV complexes. The nature of the intermediates and possible mechanisms of photosolvation are discussed.     

Solution state and complexing ability of 1,4-bis(amidomethylsulfinyl)butane toward iron(III), copper(II), cobalt(II), nickel(II), and manganese(II)

The solution state and thermodynamic stability of complexes of the new antituberculosis agent 1,4-bis(amidomethylsulfinyl)butane (L) with iron(III), copper(II), cobalt(II), nickel(II), and manganese(II) in an aqueous solution in the presence and in the absence of the nonionic surfactant Brij 35 were studied by spectrophotometry, pH potentiometry, NMR relaxation technique (T = 25 °C; variable ionic strength), and mathematical simulation. The geometry optimization of all structures was carried out by the molecular mechanics method MM2 in order to obtain data on coordination modes. In addition, the structure of 1,4-bis(amidomethylsulfinyl)butane was refined by the DFT/B3LYP/6-311++G(d,p) quantum chemical method using the IEFPCM model to take into account solvent effects. In an aqueous solution (in the concentration range of 1.3?10^–5—1?10^–3 mol L–1) and in the presence of Brij 35, 1,4-bis(amidomethylsulfinyl)butane exists as a neutral monomer. The Beer—Lambert—Bouguer law is obeyed in a wide concentration range for compound L in an aqueous solution, as well as in the presence of the surfactant, which can be used for the quantification of compound L. Iron(III), cobalt(II), and nickel(II) were shown to form 1: 1 mononuclear complexes with L; and copper(II) forms, 1: 1 and 2: 2 complexes. The presence of Brij 35 in the Cu²⁺—L system at a micellar concentration promotes the formation of a dinuclear complex.     

Alkylation of phenol with olefins in the presence of catalysts based on mesoporous aromatic frameworks

Mesoporous polyaromatic frameworks (PAFs) based on tetraphenylmethane were obtained and modified with sulfonic acid groups. The compounds were characterized by solid-state ¹³C NMR and IR spectroscopy, low-temperature nitrogen adsorption-desorption, and transmission electron microscopy. The acidities of the PAF-1-SO₃H and PAF-2-SO₃H samples determined by titration were 3.99 mmol g^–1 and 0.91 mmol g^–1, respectively. The catalytic activity of PAF-SO₃H for alkylation of phenol with linear terminal olefins was investigated. The reaction products were isomeric monoalkylphenols (C-alkylates), and alkyl phenyl ethers (O-alkylates).     

A comparative study of the reactions of fluorinated oxi- and thiiranes with acyl chlorides

The CoCl₂-catalyzed reactions of fluorinated 1,2-oxi- and thiiranes with acyl chlorides were studied. It was found that a regioselective heterocycle opening reaction resulted in two isomers having normal and abnormal structure in a ratio predetermined by the substituents in both the starting heterocycles and acyl chlorides.     

Synthesis of substituted 3-acyl-1-hydroxyindoles and azoles on their basis

A general approach to the synthesis of new 3-acetyl-substituted pyrrolo[3,4-f]indole-5,7-diones, 3-[3-(dimethylamino)acryloyl]-1-methoxypyrrolo[3,4-f]indole-5,7-diones and similar indole-5,6-dicarbonitriles has been developed. Dimethylaminoacryloyl derivatives synthesized on their basis regioselectively reacted with hydrazine hydrochlorides and hydroxylamine with the formation of the corresponding 5-substituted azoles.     

<Emphasis Type="Italic">N</Emphasis>-Allyl-substituted aminomethylene-1,1-bisphosphonates in 1,3-dipolar cycloaddition reaction with aromatic nitrile <Emphasis Type="Italic">N</Emphasis>-oxides

A reaction of N-allyl-substituted aminomethylene-1,1-bisphosphonates with aromatic nitrile N-oxides was used to obtain new aminomethylenebisphosphonates with one or two 3-arylisoxazoline rings at the nitrogen atom. NMR spectroscopy studies showed that the bisphosphonates with two isoxazoline fragments in the molecule exist in solution as a mixture of two diastereomers.     

Conjugation of indole derivatives by copper-catalyzed alkyne-azide cycloaddition

An efficient synthetic procedure to combine biologically active indole derivatives by the triazole-containing spacer in a molecule has been proposed. The procedure was based on a copper-catalyzed alkyne-azide cycloaddition of azide-containing carbazoles and N-propargyl-containing carbazoles, tetrahydrocarbazoles, and tetrahydro-γ-carbolines.     

Synthesis and properties of 1-(R-adamant-1-yl)-3-(1-propionylpiperidin-4-yl)ureas and 4-({4-[3-(R-adamant-1-yl)ureido]cyclohexyl}oxy)benzoic acids,efficient target-oriented human soluble epoxide hydrolase inhibitors

A reaction of R-adamant-1-yl isocyanates with 4-[(4-aminocyclohexyl)oxy]benzoic acid and 1-(4-aminopiperidin-1-yl)propan-1-one in DMF afforded corresponding ureas in 90—95% yield, the target-oriented inhibitors of epoxide hydrolase sEH. The ureas are characterized by reduced melting points and increased solubility in water, as well as by inhibitory activity in the range of 0.5—4.0 nmol L^–1.