Determination of nickel in standard rocks and glasses by photon activation analysis with 30-MeV bremsstrahlung

The determination of nickel in various silicate rocks and glasses by photon activation analysis with a linear electron accelerator is described. Simultaneous irradiation of the sample and comparative standards produces the ⁵⁸Ni(γ, n)⁵⁷Ni reaction, and a post-irradiation chemical separation is used in conjunction with Ge(Li) γ-spectrometry. Nickel abundances for ten standard silicate rocks and two elementally doped glasses are presented and compared with the data previously published. The method is quite simple and gives good reproducible results for nickel down to sub-p.p.m. levels.     

Atomic absorption spectrometry of traces of tri- and hexavalent chromium

Summary Atomic absorption spectrometry combined with extraction is described for the determination of tri- and hexavalent chromium. The chromium diethyldithiocarbamate chelate was used for chromium (VI), whereas hydroxyquinolate or thenoyltrifluoroacetonate chelate for chromium(III). The method is rapid and precise.

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Zusammenfassung Extraktion und darauffolgende Messung der Atomarabsorption wurden zur Bestimmung von drei- und sechswertigem Chrom verwendet. Die Chelatverbindung mit Diäthyldithiocarbamat wurde für Chrom(VI), der Chelatkomplex mit Hydroxychinolin oder Thenoyltrifluoraceton für Chrom(III) verwendet. Das Verfahren ist rasch und genau.

     

Acylation of heteroaromatic amines . Perbenzoylation of diaminopyridazines

Some diaminopyridazines such as 4,7-diaminoimidazo[4,5-d]pyridazine, 1-methyl-4,7-diaminoimidazo[4,5-d]pyridazine, 5,8-diaminopyrazino[2,3-d]pyridazine, 2,3-dimethyl-5,8-diaminopyrazino[2,3-d]pyridazine and 1,4-diaminophthalazine, all of which were prepared by the reaction of hydrazine with the respective vic-dicyanide as starting material, were reacted with benzoyl chloride in the presence of triethylamine, giving novel perbenzoylated derivatives in good yield. A dibenzoylation mechanism of the amino group has been proposed.     

Light emission from chlorine atoms formed in the dissociative excitation of HCI in a flowing afterglow of discharged argon

Light emission from Cl(5p) atoms (near 440 nm) produced in the reaction of HCl in a discharged flow of argon was investigated with a flowing-afterglow apparatus. Ionic species, most probably argon ions in metastable states, Ar^+M, were found to be responsible for the Cl(5p) production in the dissociative excitation of HCl.     

Novel rearrangement of twisted 2,4-di-alkyl 2-trans-4-trans pentadienals: An approach to cyclopentenones based on molecular mechanical consideration

Rearrangement of 2,4-di-$\text{trans}$-pentadienals $\text{IVa-d}$ was described as a consequence of the successive alkyl substitutions on the C-2 and C-4 positions. ¹H-FT nmr spectroscopy suggested that the reaction involves ketene $\text{VIII}$ as an intermediate.     

Synthesis of bis(alk-3-en-1-ynyl)benzene with either E- or Z-configuration via a one-pot three-component coupling reaction and its optical properties

A convenient, efficient and stereoselective synthesis of a range of bis(alk-3-en-1-ynyl)benzenes with E- and Z-configuration is described. The protocol involves Cu-mediated cross-coupling reaction of (E)- and (Z)-alk-1-enyldisiamylboranes with (trimethylsilyl)ethynyl bromide and Pd/Cu-catalyzed cross-coupling reaction with diiodobenzene. The sequential cross-coupling reaction proceeds readily under extremely mild conditions in a one-pot manner to afford bis(alk-3-en-1-ynyl)benzenes in good to excellent yields. The optical properties of the products are also described.     

OBSERVATION OF THE PICOSECOND TIME-RESOLVED SPECTRUM OF SQUID BATHORHODOPSIN AT ROOM TEMPERATURE

Difference spectra between squid rhodopsin and its bathorhodopsin at room temperature were measured ca. 150 ps and ca. 500 ps after the excitation at 347.2 nm by a double-beam picosecond time-resolved spectrometer. The spectra measured showed a red shift of the isosbestic point between squid rhodopsin and its bathorhodopsin and a lower ΔA_max/ΔA_min value compared with those measured at low temperatures by conventional spectrophotometry.     

Microwave spectroscopic study on the molecular structure and the quadrupole coupling constants of thionyl chloride

Microwave spectra of thionyl chloride, SO³⁵Cl₂ and SO³⁵Cl³⁷Cl, in the frequency range 8–25 GHz have been analyzed. The rotational constants have been obtained from the low J transition frequencies. The r_S coordinates of Cl atoms and the r_o structure have been evaluated with some assumptions: r(S-O) = 1.435 ± 0.011± Å, r(S—Cl) = 2.072 0.005 Å, ∠ OSCl = 108.00 ± 0.06°, ∠ ClSCl = 97.15 ± 0.30°. Nuclear quadrupole coupling constants have been obtained for the SO³⁵Cl₂, species: x_aa = ?25.02 ± 0.04 MHz, x(_bb = ?0.25 ± 0.04 MHz, X_cc = 25.27 ± 0.08 MHz, and X_zz = ?96.75 MHz. The values obtained are compared with those of other workers.     

Radical-initiated homo- and copolymerization of cyanomethyl methacrylate

The kinetics of cyanomethyl methacrylate (CyMA) homopolymerization was investigated in acetonitrile with azobisisobutyronitrile as initiator. The rate of polymerization R_p was expressed by R_p = k[AIBN]^0.49[CyMA]^1.2 and the overall activation energy was calculated as 72.3 kJ/mol. Kinetic constants for CyMA polymerization were obtained as follows: k_p/k = 0.10 L^1/2s^?1/2; 2fk_d = 1.57 × 10^?5s^?. The relative reactivity ratios of CyMA(M₂) copolymerization with styrene (r₁ = 0.15, r₂ = 0.29) and methyl methacrylate (r₁ = 0.43, r₂ = 0.75) in acetonitrile were obtained. Applying the Q-e scheme (in styrene copolymerization) led to Q = 1.64 and e = 0.98. The glass transition temperature T_g of poly(CyMA) was observed to be 91°C by thermomechanical analysis. Thermogravimetry of poly(CyMA) showed a 10% weight loss at 265°C in air.