The rotational and vibrational spectra,structure and dipole moment of 1,3-dioxole-2-thione

Rotational and centrifugal distortion constants are determined for the ground state and several excited states of the lowest vibrational mode of l,3-dioxole-2-thione, the “envelope” ring-bending mode. The structure of the molecule is planar. The A-constant is 1% larger than that of 1,3-dioxole-2-one (vinylene carbonate), which indicates small changes in ring-geometry on substituting CS for CO. The dipole moment of 1,3-dioxole-2-thione deduced from Stark-effect measurements is (1.60 ± 0.02) × 10^?29 Cm (4.81 ± 0.06 D). IR and Raman spectra lead to a complete analysis of the normal modes of vibration, based partially on a normal coordinate calculation.     

An inter-laboratory comparison study for the determination of copper and lead from the wastewater of printed circuit board manufacturing industry in Pakistan

This inter-laboratory comparison study was arranged for 28 laboratories from different public and private sector organizations in Pakistan having wastewater testing capabilities aimed at improving the quality and comparability of test results. This national inter-laboratory study was started in December 2003 and completed in July 2004. Laboratories were invited to analyze the wastewater collected from printed circuit board (PCB) industry for lead and copper contamination. The samples fulfill the criteria for homogeneity and stability as done by the reference laboratory. The results obtained from participating laboratories were analyzed in terms of Hampel Test for outliers, while the performance evaluation of the participating laboratories was done on the basis of Z-score. An assigned value derived from the participant's results was compared with a reference value provided by a reference laboratory. Overall >50% of the participating laboratories have shown good performance in this PT-program     

Synthesis, Characterization, and Biological Activity of n -Tributyltin Derivatives of Pharmaceutically Active Carboxylates

 Tributyltin(IV) derivatives of six different pharmaceutically active carboxylates were synthesized. The complexes were characterized by different analytical techniques (elemental analysis; infrared, NMR, and mass spectroscopy). ¹¹⁹Sn NMR data were also recorded in six different coordinating and non-coordinating solvents. The antibacterial activities of the compounds were tested using ten different bacteria relative to the reference drugs ampicillin and cephalexin.     

Magnetic ordering in doped Cd(1-x)Co(x)Se diluted magnetic quantum dots

In this study, we report structural, vibrational, and magnetic data providing evidence of random ion displacement in the core of CdSe quantum dots on the Cd(2+) sites by Co(2+) ions (between x = 0 and 0.30). Structural evidence for core doping is obtained by analyzing the powder X-ray diffraction (pXRD), data which exhibits a linear lattice compression with increasing Co(2+) concentration, in accord with Vegard's law. Correlated with the pXRD shift, a hardening of the CdSe longitudinal optical phonon mode and a new local vibrational mode are observed which track Co(2+) doping concentration. Consistent with the observed core doping, superconducting quantum interference device (SQUID) measurements indicate a surprising increase for the onset of spin glass behavior by an order of magnitude over bulk Co:CdSe. Correlation of SQUID results, pXRD, and Raman measurements suggests that the observed enhancement of magnetic superexchange between Co(2+) dopant ions in this confined system arises from changes in the nature of coupling in size-restricted materials.     

Conductometric Determination of the Stability Constants of the Inclusion Complexes of Alkali Cations with [22-DD] Diaza Crown Ether, [211] and [221] Cryptands in Acetonitrile

An equilibrium study concerning the association of Na⁺, K⁺, Rb⁺ and Cs⁺ with 4, 7, 13, 18-tetraoxa-1,10-diazabicyclo [8, 5, 5]-eicosane [211], 4, 7, 13, 16, 21-pentaoxa-1, 10-diazabicyclo [8, 8, 5]-tricosane [221] and 4, 13-didecyl-1, 7, 10, 16-tetraoxa-4, 13-diazacyclooctadecane [22-DD] in acetonitrile has been carried out at 25 °C by using a conductometric technique. The observed molar conductivity, Λ, of a test solution was found to decrease significantly for mole ratios less than 1:1 upon the addition of the complexing ligand. A model based on 1:1 stoichiometry has been used to analyze the conductivity data. The data have been fitted according to a non-linear least-squares analysis that provides the stability constant, K, and the molar conductivity, Λ_c, for each cation – ligand inclusion complex. The binding sequences were found to follow the order: Na⁺ > K⁺ > Rb⁺ ≫ Cs⁺ (K ≈ 0) for [211], Na⁺ > K⁺ > Rb⁺ > Cs⁺ for [221] and K⁺ > Na⁺ > Rb⁺ > Cs⁺ for [22-DD] complexes. Trends in ionic conductivities of complexed ions are also discussed.     

Microbial transformation of rubijervine

Preparative-scale fermentation of rubijervine (1), the known 22,26-epiminocholestane Veratrum alkaloid, with Cunninghamella echinulata ATCC 9244 has resulted in the isolation of the new metabolites 7alpha-hydroxyrubijervine (2) and solanid-5-ene-3beta,12alpha-diol-1-one (3). Structure elucidation of these metabolites was based primarily on 1D- and 2D-NMR analyses. The microbe C. echinulata ATCC 9244 was able to metabolize rings A and B of rubijervine but failed to metabolize rings C, D or its N-containing side chain, a finding which is analogous to the results of previous fermentation studies of steroidal alkaloids.     

Solvent effect on thermal degradation of plasticized para-substituted polystyrenes

The thermal effect on stability of a series of para-substituted polystyrenes with methyl, methoxy and α-methyl substituents in various solvents was studied in the temperature range of 298-363 K. They gave a monomer fluorescence as a minor part and excimer fluorescence as a major part. Thermal heating of para-substituted polystyrenes shows a decrease in both monomer and excimer fluorescences in all used solvents. Thermal heating causes a small fluorescence quenching effect at lower temperatures in solution but becomes very dominant at higher temperatures. Added terephthalate and phthalate plasticizers to these para-substituted polystyrenes caused a quenching of both monomer and excimer fluorescences without the formation of exciplex emission. The thermal quenching processes of the plasticized polymers were accompanied by a change in the structure of the fluorescence spectra at high heating temperatures. This may indicate that thermodestruction of these polymers starts from a random chain scission. The change in solvent polarity has considerable effect on fluorescence quenching but it has a minor effect on the thermal degradation of these polymers. The binding energies for excimer formation were calculated in the used solvents.     

Rapid microwave assisted synthesis of 3-substituted 4-thioxo-oxazolidin-2-ones

The microwave assisted thionation of 3-substituted 4-imino-oxazolidin-2-ones with hydrogen sulfide in dichloromethane-pyridine afforded 3-substituted 4-thioxo-oxazolidin-2-ones.     

Synthesis and reactivity of 3-aralkoxy-4-imino-imidazolidin-2-ones: a novel class of 4-iminohydantoins

Reactions of diethylphosphonoalkyl α-aminonitriles with 1,1′-carbonyl-diimidazole or 1,1′-carbonyl-di-(1,2,4-triazole) and O-substituted hydroxylamines under acidic conditions gave 3-alkoxy-4-imino-imidazolidin-2-ones, whereas in presence of triethylamine 4-alkoxy(aralkoxy)imino-imidazolidin-2-ones were formed.     

Towards more controlled poly(n-butyl methacrylate) by atom transfer radical polymerization

The homogeneous controlled/‘living’ free radical polymerization of n-butyl methacrylate in toluene or o-xylene at 90 °C, in bulk and in solution, using the novel combination of the catalyst bis-triphenylphosphine iron(II)chloride tetrahydrate (FeCl₂ · 4H₂O(PPh₃)₂) with ethyl 2-bromoisobutyrate ((CH₃)₂CBrCO₂Et)) and α,α-dichloroacetophenone (CHCl₂COPh) as initiators has been investigated. The rate of polymerization initiated by the two initiators exhibited first-order kinetic with respect to the monomer. A linear increase of the number-average molecular weight (M_n) versus monomer conversion was observed for these systems. Among the two initiation systems, ethyl 2-bromoisobutyrate gave the fastest polymerization rate. A system with Fe³⁺ added at the beginning of the polymerization was examined and the lowest polydispersity (M_w/M_n∼1.2) was found when 10% Fe³⁺, relative to Fe²⁺ was added.