Tomography of high harmonic generation in a cluster jet

Tomographic measurement of high harmonic generation in a cluster jet was demonstrated by programming the cluster density distribution with a laser machining technique. The growth of harmonic energy with the propagation of the pump pulse was resolved by scanning the end of the argon cluster distribution in the path of the pump pulse. A downstream shift of the position of rapid growth and a decrease of the slope with increasing backing pressure as results of changes in the phase-matching condition were observed, which explains the presence of an optimal backing pressure.     

Organoboranes: XXVIII. Convenient procedures for the synthesis of borinane

Convenient syntheses of the six-ring boracyclane, borinane, have been developed. Hydroboration of 1,4-pentadiene with two molar equivalents of 9-borabicyclo-[3.3.1]nonane (9-BBN) in a suitable solvent, followed by reaction of the resulting trialkylborane with one molar equivalent of the borane-tetrahydrofuran complex (BH₃·THF) or the borane-dimethyl sulfide complex (BH₃·SMe₂, BMS), leads to the cyclization of the pentadiene moiety, forming borinane with the regeneration of two molar equivalents of 9-BBN. Complete separation of the two dialkylboranes by fractional crystallization from solvents such as THF, 1,2-dimethoxyethane (DME), 1,3-dioxolane, n-hexane, n-pentane and hexane plus dioxolane was unsuccessful. Treating the reaction mixture in hexane with the requisite amount of triethylamine (Et₃N) led to selective complexation with borinane. By cooling the reaction mixture to ?78°C, it was now possible to crystallize out the uncomplexed 9-BBN almost quantitatively (98%). Alternatively, borinane could be precipitated selectively from the hexane reaction mixture as its bis-adduct with either N, N, N′, N′-tetramethylethylenediamine (TMED) or 1,4-diazabicyclo[2.2.2]octane (DABCO). Free borinane was readily liberated from its amine adducts by treatment with boron trifluoride etherate (BF₃·OEt₂). Finally, the two dialkylboranes were readily separated by fractional distillation, using a specially designed reaction setup. Distillation at about 70–80°C and 0.01 mm pressure led to the clean distillation of borinane, leaving the 9-BBN, as a residue, readily recycled in subsequent preparations. Alternatively, once free borinane has been obtained, it can be used to hydroborate 1,4-pentadiene in place of 9-BBN. Treatment of the product with BH₃·THF or BH₃·SMe₂ converts two moles of borinane into three, without the formation of a by-product.     

Synthesis of (±)-coerulescine and a formal synthesis of (±)-horsfiline

A straightforward synthesis of (±)-coerulescine and (±)-horsfiline has been established from 3-formyl-3-phenylpyrrolidine employing 4-hydroxypiperidine as the starting material. There are two remarkable steps for the synthesis of (±)-coerulescine and (±)-horsfiline. One is the rapid access to produce 3-formyl-3-phenylpyrrolidine by Lewis acid-catalyzed rearrangement of 3,4-dihydroxy-4-phenylpiperidine. The other key step is an intramolecular electrophilic cyclization from 3-benzylcarbamoyl-3-phenylpyrrolidine to the 3,3-spirocyclic 2-oxindole ring skeleton.     

Catalytic epoxidation of α,β-and β,γ-unsaturated bicyclic ketones with hydrogen peroxide

The possibility of preparing epoxides from α,β-and β,γ-unsaturated bicyclic ketones formed as by-products in liquid-phase oxidation of cyclohexane with atmospheric oxygen (a stage in production of caprolactam, adipic acid, and other products) was examined. The reaction products were analyzed by gel chromatography and mass spectrometry.     

Thermal analysis of hydrazinium metal sulphates and their hydrazinates

Thermal analysis of hydrazinium metal sulphates, (N₂H₅)₂ M(SO₄)-I, and their hydrazinates, (N₂H₅)₂−M(SO₄)₂3N₂H₄−II, whereM=Fe, Co and Ni have been investigated using thermogravimetry and differential thermal analysis. Type II compounds on heating decompose through an intermediate I and metal suphlate to the respective metal oxides.     

Synthesis of streptorubin B core

A straightforward synthesis of streptorubin B core structure has been established starting from trans-4-hydroxyproline. The core structure of streptorubin B is constructed in an intramolecular ring-closing metathesis as the key step.     

Parcel model for peak shapes in chromatography numerical verification of the temporal distortion effect to peak asymmetry

The traditional plate concept has been reassessed and improved to a parcel matrix model, which can be used to imitate the chromatographic behavior of a hypothetic column on a computer worksheet. Under programmed conditions, various peak shapes (nearly Gaussian, and with prolonged or fronting tails) are generated. The peak tailing has been separated into two major fractions: spatial and temporal. The former fraction is caused by the retention nature of a column, whereas the latter is induced by the observer's relative position and the changing of the zone broadening rate. The temporal distortion effect can be identified qualitatively and quantitatively through a normalized peak-overlapping process. In general, a chromatographic peak may carry a prolonged (or normal type) tail under linear isotherms, while both prolonged and fronting tails will appear under non-linear conditions. The temporal distortion is proved to be significant, and may be regarded as the major cause of peak asymmetry in most cases. This is in contrast to the conclusions of many previous studies. The model is also eligible to simulate chromatographic peaks for various injection sizes.     

Cooperative Study of Precision and Accuracy on the Determinations of Around-Ppb Levels of Copper and Lead in Environmental Waters

The results of a series of inter-laboratory cross-check on the determinations of ppb and sub-ppb levels of copper and lead in environmental samples are described. Thirteen laboratories participated during a five-stage comparison. Seven analytical methods and two pre-concentration procedures were performed on certified and real samples. For controlled and blind standards at higher concentration levels (10 ppb or above) the data reported by different participants show good agreement for both elements regardless of the method chosen. However, for samples having lower concentrations (1-10 ppb level), the relative standard deviation (R.S.D.) and bias increased. A high degree of scattering on data were demonstrated for a deep ocean water at less than 1 ppb level. The results of the present study give direct comparison between different analytical methods, and also reflect the average aptitude of analytical laboratories in Taiwan on the measurements of copper and lead in environmental samples.     

Synergistic extraction of uranyl ion with 1-phenyl-3-methyl-4-benzoylpyrazolone-5 (HPMBP) and diphenyl sulfoxide (DPSO), tri-n-butyl phosphate (TBP) or tri-n-octylphosphine oxide (TOPO)

Synergistic extraction of uranyl ion with 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (HPMBP) and oxo donors with widely varying basicity, viz. diphenyl sulfoxide (DPSO), tri-n-butyl phosphate (TBP) and tri-n-octylphosphine-oxide (TOPO) has been studied at various fixed temperatures. Results indicate that the equilibrium constants in the organic phase for addition reactions (K_S) with these donors follow their order of basicity (K_H) viz. DPSO (0.033)<TBP (0.16)TOPO (8.9) with log K_S values of 3.70, 4.28 and 6.45, respectively. The thermodynamic parameters associated with the formation of these systems have been evaluted by the temperature coefficient method. The results indicate that the complex in the organic phase for DPSO and TBP is stabilized only by enthalpy, whereas both enthalpy and entropy contribute to the stabilization of the TOPO complex. Also, enthalpy contribution is more prominent as compared with the UO ₂ ²⁺ /HTTA/TOPO system, where both enthalpy and entropy contribute almost equally.