A new and facile synthesis of 3-(2-aryl-6-nitro-1H-indol-3-yl)quinoline-2,4(1H,3H)-diones by sodium alginate as biopolymeric catalyst

Research on Chemical Intermediates - New 3-(2-aryl-6-nitro-1H-indol-3-yl)quinoline-2,4(1H,3H)-diones were synthesized, and good-to-excellent yields were achieved through one-pot, three-component...     

Complex polymer architectures through dimethoxymethyl 1,1‐diphenylethylene derivatives

The reactions of polystyryllithium and potassium on dimethoxymethyl 1,1‐diphenylethylene derivatives were studied in different solvents. In a polar medium, A₃ and A₆ star types were formed according to the stoichiometry, whereas in a nonpolar medium, hyperbranched structures were synthesized. Extensions of an already proposed mechanism in polar and nonpolar media were examined. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3329–3335, 2003     

Carbamate Formation and Amine Protonation Constants in 2-Amino-1-Butanol–CO<Subscript>2</Subscript>–H<Subscript>2</Subscript>O System and Their Temperature Dependences

The apparent protonation constant of an amino butanol (AB) and its carbamate formation constant in the CO₂–H₂O–AB system were determined at T = 298.15–328.15 K, and at various ionic strengths up to 0.2 mol·L^?1 by potentiometric titration. The Debye–Hückel equation was used to extrapolate the protonation constants to zero ionic strength. The variation of the thermodynamic equilibrium constant for carbamate formation with temperature was modeled according to the relationship of log₁₀ K₁ = 280.91/T ? 0.1105, while the temperature dependency of the amine protonation constant was correlated by log₁₀ K₂ = 1926.53/T + 2.9482. Van’t Hoff type plots of the pK values showed linear relationships indicating that the standard enthalpy changes of reaction are constant over this range of temperatures. Hence, our current findings are crucial for designing efficient unit operations involving separation of CO₂ from natural or flue gases.     

Determination of gasoline and diesel residues on wool,silk, polyester and cotton materials by SPME–GC–MS

The identification of ignitable liquids is very important and challenging aspect in arson crime investigations. The detection of gasoline and diesel fuel components using solid phase micro-extraction prior to gas chromatography–mass spectrometry for the forensic analysis of fire debris has been carried out. Previous works show that the absorption characteristics of the substrate are one of the most important factors in determining the evaporation rate of the accelerants. In order to determine the presence of the fuel residues, four of the most common substrate materials were tested in this work; wool, cotton, silk and polyester. The obtained results indicate that both gasoline and diesel fuel accelerants persisted longer on wool and silk than on the other selected substrates. Such information illustrates the influence of fuel persistence times after extinguishing and the best materials to be scanned for ignitable liquids at the fire scene.     

Die ionisierenden Potentialwellen beim Funkendurchschlag

Extending earlier studies on spark breakdown, the development of the impulse prebreakdown streamers leading to complete breakdown were investigated. By taking advantage of the proportionality between point potential and length of the positive Lichtenberg figure produced, the potential of the streamer tips progressing from a point anode towards a plane cathode were determined. It was found that the streamer tip potential decreases as streamer advances. At voltages much lower than sparking potential this decrease is rapid. By approaching the sparking potential the loss of tip potential diminishes considerably near the anode. The decrease of potential remains very rapid near the cathode until sparking potential is reached. At the cathode the tip potential increases with the applied potential. At a certain value electrons are emitted from the cathode under the influence of high tip fields. These electrons are accelerated towards the tips forming avalanches by collision. These avalanches appear on the photographic film as minute dots whose number and density depend on the intensity of tip fields. If the applied potential exceeds the sparking voltage, tip potentials are recorded on the cathode between 15 and 25 kV. The avalanches formed in the high intensity field region reach the critical size and form negative, anode — directed streamers. These streamers appear on the film as negative Lichtenberg figures. This ionising potential wave, known as return stroke, travels along the channel of the positive primary streamer. It increases its ionisation to such a degree that the main stroke can take place.     

p-4He elastic scattering at 2.68 GeV

The p-⁴He elastic differential cross section has been measured at a kinetic energy of 2.68 GeV. The momentum transfer region studied is t = 0.15–0.66 (GeV/c)². The cross section displays a shallow first minimum and shape very similar to recent data at 1 GeV.     

Preparation of a deoxynucleoside thiophosphoramidite intermediate in the synthesis of nucleoside phosphorodithioates

A general synthetic scheme for preparation of thiophosphoramidite intermediates, chloro-N,N-diisopropylaminothiomethoxyphosphine, 2, and 3′-O-deoxythymidine derivatives of N,N-diisopropylaminothiomethoxyphosphine, 4, is described. These intermediates can be used to synthesize dithiophosphate deoxyoligonucleotide analogues.