Oxidation of hydroxylamine by ferricyanide in presence of zinc sulfate: A rapid method for estimating hydroxylamine and hydrazine in a mixture

The direct titration of alkaline ferricyanide in presence of zinc sulfate with hydroxylamine sulfate has been studied. A clear white precipitate of zinc potassium ferrocyanide indicates the end-point. Hydroxylamine is oxidized to nitric acid and water, and millingram-quaantities of hydroxylamine; can be determinred. In the absence of zinc sulfate and in weakly alkaline medium, hydrazine and hydroxylamine are converted to nitrogen, while in presence of zine sulfate hydrazine is oxidized to nitrogen By ferricyanide oxidation of a mixed sample uinler different conditions, hydrarine and hydroxylamine when present together can be determined rapidly.     

Novel polymer patterns formed by lithographically induced self-assembly (LISA)

A variety of self-assembly patterns, e.g., concentric rings, rods, and pillars, in polymer thin film have been achieved by lithographically induced self-assembly (LISA) in this study. The variations of the LISA patterns are controlled by many operation factors, such as the choice of the polymers, mask topology, process temperatures, surface tension, and so forth. It was found that as the inter- and intramolecular hydrogen bond interactions were incorporated into the polymer [poly(methyl methacrylate-co-methacrylic acid)], novel LISA patterns such as rods and corresponding arrays (concentric ring, triangle, hexagonal, etc.) were formed, in addition to the pillar arrays formed in poly(methyl methacrylate) under the same experimental conditions. The origins of the rod array are determined by the topology of the masks. Under a plain mask, the patterns developed from any nonuniform defects (spots) on the mask or polymer thin film and propagated outward. However, under a mask with protruding flat patterns, the rod patterns started along the edge of the protrusions and propagated inward. By increasing the process temperature, those novel rods and corresponding array patterns could transform back to pillar or pillar arrays.     

Octahedral ruthenium(II) alkenyl complexes containing {\text{N}}{\text{S}} coordinated heterocyclic ligands

Summary Hexacoordinated ruthenium(II) alkenyl complexes of the type Ru(CO)(CR=CHPh)( )(PPh₃)₂ have been prepared from coordinately unsaturated -vinyl complexes [Ru(CO)Cl(CR=CHPh)(PPh₃)₂] (R = H or Ph) and the sodio-derivative of the containing heterocyclic ligands [ = 3,4-substituted 1,2,4-triazole-5-thione and 5-alkylthio-1,3,4-thiadiazole-2-thione] in a CH₂Cl₂/MeOH mixture at ambient temperature. The complexes were characterized by their elemental analysis, i.r., ¹H and ³¹P n.m.r. spectra. An octahedral structure with transphosphorus ligands has been assigned on the basis of the spectral data.     

Structural, energetic, electronic, bonding, and vibrational properties of Ga3O, Ga3O2, Ga3O3, Ga2O3, and GaO3 clusters

The results of density functional theory based calculations on Ga3O, Ga3O2, Ga3O3, Ga2O3, and GaO3 clusters are reported here. A preference for planar arrangement of the constituent atoms maximizing the ionic interactions is found in the ground state of the clusters considered. The sequential oxidation of the metal-excess clusters increases the binding energy, but the sequential removal of a metal atom from the oxygen-excess clusters decreases the binding energy. The increase in the oxygen to metal ratio in these clusters is accompanied by increase in both electron affinity and ionization potential. The ionization induced structural distortions in the neutral clusters are relatively small, except those for Ga3O2. In anionic (cationic) clusters, the added (ionized) electron is shared by the Ga atoms, except in the case of GaO3. The vibrational frequencies and charge density analysis reveal the importance of the ionic Ga-O bond in stabilizing the gallium oxide clusters considered in this study.     

Kinetics of vinylation of 4′-bromoacetophenone with n-butyl acrylate using palladacycle catalyst

The kinetics of vinylation of 4′-bromoacetophenone (4′-BAP) with n-butyl acrylate (n-BA) has been studied using palladacycle catalyst precursor 1, in the presence of sodium acetate (NaOAc) as a base and tetrabutylammonium bromide (TBAB) as a promoter in N-methyl-2-pyrrolidinone (NMP) solvent. The rate was found to be first order with respect to 4′-BAP, fractional order with the catalyst, and first order tending to zero order with NaOAc concentration. The rates passed through a maximum with variation of TBAB and n-butyl acrylate concentrations. The rate data have been analyzed to propose an empirical model, which is in good agreement with the mechanism already established for Heck reactions using palladacycle catalysts.     

Highly enantioselective Friedel-Crafts alkylations of pyrroles and indoles with alpha'-hydroxy enones under Cu(II)-simple bis(oxazoline) catalysis

Remarkably high and regular enantioselectivities are obtained in Friedel-Crafts alkylation reactions involving alpha'-hydroxy enone templates and Cu(II)-bis(oxazoline) complexes as catalysts. The simple elaboration of adducts provides a route to enantioenriched aldehydes, carboxylic acids, and ketones containing the pyrrole and indole frameworks.     

A general regiospecific synthesis of (+) 11-deoxyanthracyclinones

An elegant regiospecific approach for the synthesis of 11-deoxyanthracyclinones is described, involving the Diels-Alder reaction of an appropriate diene with a suitably substituted naphthalene C-D ring synthon.     

Capillary Electrophoretic Determination of Gatifloxacin from Pharmaceutical Preparation

Capillary zone electrophoresis has been used for the determination of gatifloxacin from its pharmaceutical preparation (tablets), using fused silica capillary. Separation was performed after hydrodynamic injection; the separation was achieved by applying 21 Kv voltage. Phosphate buffer solution (pH 9.5) was used as separation electrolyte. Detection was at 280 nm using a UV- detector. Under these experimental conditions the analysis takes 8 min. A linearity range for gatifloxacin was between 20.0 g mL^–1 to 60.0 g mL^–1. The method was validated and was found to be specific, precise, accurate, reproducible and robust and can be applied for the routine analysis of gatifloxacin from formulation and bulk drug.     

Kinetics and mechanism of bromamine-T oxidation of some cyclic ketones in acidic media

Kinetics of the oxidation cyclopentanone and cyclohexanone by bromamine-T(BAT) have been reported in perchloric acid media. A zero order dependence to BAT and first order dependence on both ketones and hydrogen ion concentrations have been observed. Observed stoichiometry, zero effects of ionic strength of the medium and p-toluenesulphonamide (TSA) and a negative dielectric effect point to a mechanism involving acid catalysed enolisation of ketones in the slow and rate determining step, followed by its subsequent fast interaction with BAT giving corresponding 1,2-diketones as final products. A solvent isotope effect (kD₂O/kH₂O = 2.0–2.2 (35°), 2.1–2.3 (40°) and 2.2–2.4 (35°), 2.3–2.5 (40°) for cyclopentanone and cyclohexanone, respectively) has been observed. Various thermodynamic parameters have been computed.