Photometric determination of malathion with molybdenum

A photometric method for the determination of malathion is described. Malathion dissolved in carbon tetrachloride is hydrolysed at room temperature with sodium ethoxide to dimethyl dithiophosphate (DMDTP) and fumarate. The DMDTP is converted into a molybdenum-DMDTP complex and determined spectrometrically.     

Homogeneous isotopic exchange between nickel(II) and bis(diethyldithiocarbamato)nickel(II) complex

Isotopic exchange behaviour of bis(diethyldithio carbamate) nickel(II) complex with nickel(II) in chloroform and methanol medium was studied. The studies were carried out at different temperatures varying the concentration of both metal ion and the complex. The results show that the complex is labile in the kinetic sense. Increase in temperature increases the isotopic exchange rate. The increase in concentration also results in enhancement of the rate of reaction.     

Isotope exchange between bis/diethyl dithiocarbamate/ copper/II/ complex and Cu2+ ion

Isotope exchange behaviour of bis/diethyl dithiocarbamate/ copper/II/ complex has been studied at 30 °C and 40 °C varying the concentration of the complex and metal ion. Results indicate that the complex is labile in chloroform dimethyl sulphoxide medium. Increase in concentration has significant effect on the rate of the reaction. Similarly the increase in temperature increased the rate of the reaction.     

Effects of soluble surfactants on the deformation and breakup of stretching liquid bridges

Surfactants are routinely used to control the breakup of drops and jets in many applications such as inkjet printing, crop spraying, and DNA or protein microarraying. The breakup of surfactant-free drops and jets has been extensively studied. By contrast, little is known about the closely related problem of interface rupture when surfactants are present. Solutions of a nonionic surfactant, pentaethylene glycol monododecyl ether, or C12E5, in water and in 90 wt % glycerol/water are used to show the effects of surfactant and viscosity on the deformation and breakup dynamics of stretching liquid bridges. Equilibrium surface tensions for both solutions can be fitted with the Langmuir-Szyskowski equation. All experiments have been done at 24 degrees C. The critical micelle concentrations for C12E5 are 0.04 and 0.4 mM in water and the glycerol/water solution, respectively. With high-speed imaging, the dynamic shapes of bridges held captive between two rods of 3.15 mm diameter are captured and analyzed with a time resolution of 0.1-1 ms. The bridge lengths are 3.15 mm initially and about 5-7 mm at pinch-off. Breakup occurs after stretching for about 0.2-0.3 s, depending on the solution viscosity and the surfactant concentration. When the liquid bridges break up, the volume of the sessile drop left on the bottom rod is about 3 times larger than that of the pendant drop left on the top rod. This asymmetry is due to gravity and is influenced by the equilibrium surface tensions. Surfactant-containing low-viscosity water bridges are shown to break up faster than surfactant-free ones because of the effect of gravity. With or without surfactant, water bridges form satellite drops. Surfactant-containing high-viscosity glycerol/water bridges break up more slowly than surfactant-free ones because of strong viscous effects. Moreover, the shapes of the sessile drops close to breakup exhibit a "pear-like" tip; whether a satellite forms depends on the surface age of the bridge before stretching commences. These unexpected effects arising from the addition of surfactants are due to the capillary pressure reduction and Marangoni flows linked to dynamic surface tension.     

Synthesis and use of chiral substituted benzenes containing 1,2-diols protected as cyclic acetals

1,2-Dihydroxy benzenes have been protected as cyclic diacetals using 2,3-butane dione. These diacetals are extremely robust and can be further chemically diversified and resolved with chirality embedded in the 1,4-dioxane ring attached to the aromatic back bone as a result of the anomeric effect. These systems can serve as ligands, auxiliaries or organocatalysts for asymmetric synthesis.     

Marinocyanins,cytotoxic bromo-phenazinone meroterpenoids from a marine bacterium from the streptomycete clade MAR4

Six cytotoxic and antimicrobial metabolites of a new bromo-phenazinone class, the marinocyanins A-F (1–6), were isolated together with the known bacterial metabolites 2-bromo-1-hydroxyphenazine (7), lavanducyanin (8, WS-9659A) and its chlorinated analog WS-9659B (9). These metabolites were purified by bioassay-guided fractionation of the extracts of our MAR4 marine actinomycete strains CNS-284 and CNY-960. The structures of the new compounds were determined by detailed spectroscopic methods and marinocyanin A (1) was confirmed by crystallographic methods. The marinocyanins represent the first bromo-phenazinones with an N-isoprenoid substituent in the skeleton. Marinocyanins A-F show strong to weak cytotoxicity against HCT-116 human colon carcinoma and possess modest antimicrobial activities against Staphylococcus aureus and amphotericin-resistant Candida albicans.     

Highly stable Ag nanoparticles in agar-agar matrix as inorganic–organic hybrid

A novel synthesis of inorganic–organic hybrid films containing well dispersed and almost uniform size Ag nanoparticles in agar-agar matrix has been reported. The films are found to be highly stable for more than a year. The colloidal particles of Ag can be obtained in large quantities in the form of a film or in the gel form when dispersed in agar-agar or by dissolving in a suitable solvent as solution. Characterization has been done by UV–visible spectroscopy and TEM. The hybrid may be of interest to study third-order non-linear susceptibility.     

Kinetics of dissociation of tris-2,2′-bipyridyl-iron(II) cation in aqueous acetic acid solutions

The kinetics of dissociation of tris-2,2′-bipyridyl-iron(II) complex ion have been examined in aqueous acetic acid solutions. The reaction is first order in the complex ion; the dependence of rate on H⁺ is somewhat like that observed in aqueous solutions approaching a limiting value at higher H⁺ concentrations. The influence of solvent composition on the reaction rate under acid-dependent and acid-independent conditions shows an initial retardation by acetic acid. The argument of ion-pair formation based on decrease of dielectric constant proposed to explain the kinetics in other aqueous solvent media was found useless to explain the behavior in acetic acid solutions. Other solvent parameters also did not provide satisfactory correlation with the kinetic results, thus, indicating the operation of more complex microscopic solute-solvent and solvent-solvent interactions. While solvent effects play some part in the rate process, the rate of reaction would tend to zero in the absence of H₂O and H⁺. This interesting observation proved useful in proposing a reaction mechanism that is consistent with the rate behavior over the entire range of solvent composition. The activity of water in the reaction medium is controlled by the content of acetic acid which can effect the structure of water through operation of hydrophobic forces and formation of hydrates. While acetic acid cannot possibly fulfill the role of water in occupying the vacated coordination position, the anomalous rise in rate even under some water deficient conditions seems to be related to the coordinating ability of HSO₄^? derived from H₂SO₄ present in the solution.     

Supramolecular functionalization of electron-beam generated nanostructures

Electron-beam lithography was used to pattern poly(styrene-co-(methyldiaminotriazine) styrene) (PS-Triaz). These polymer nanopatterns were utilized as molecular scaffolds for assembling complementary thymine-functionalized CdSe-ZnS quantum dots (Thy-QDs) via three-point hydrogen-bonding molecular recognition. This interaction was very specific, with N-methyl thymine-functionalized QDs (MeThy-QDs) not depositing on the surfaces. The "lock and key" specificity of the assembly is mirrored in the disassembly process, where complete removal of the QD was observed using a competing thymine guest.