Diphenylamine as an n and π donor in the solid-state reaction of 2,4-dinitrotoluene with diphenylamine

The kinetics and mechanism of the reaction of 2,4-dinitrotoluene with diphenylamine were studied in the solid state. The reaction product is a charge transfer complex with a localized intermolecular interaction as shown by uv and ir spectroscopy. The solid-state studies were complemented by some NMR studies in CCl₄. A novel feature of the study reveals that diphenylamine in this case is a much more powerful n donor than a π donor.     

Synthesis and ion-exchange properties of thermally stable stannic selenite

Stannic selenites have been synthesized under a variety of conditions. The most stable sample is prepared by mixing 0-0.5M solutions of stannic chloride and sodium selenite in the ratio of 1:1 at pH 1. It is a bifunctional amorphous material. A tentative structure has been proposed on the basis of chemical composition, pH titrations, infrared and thermogravimetric analyses. Its ion-exchange capacity is 0.75 and 0.73 meq g after drying at 50 degrees and 500 degrees respectively. Its analytical importance has been established by the following quantitative separations: Cu(2+) from Ni(2+), Co(2+), Fe(3+), Ga(3+) and In(3+), Fe(3+) from Pb(2+) and Sc(3+), and Sc(3+) from VO(2+).     

Remarkably facile hexatriene electrocyclizations as a route to functionalized cyclohexenones via ring expansion of cyclobutenones

This Communication describes a cascade reaction sequence that leads to highly functionalized cyclohexenones starting from reaction of cyclobutenones with alpha-lithio-alpha,beta-unsaturated sulfones and amides. The hexatriene-cyclohexadiene cyclization steps presumed to be involved in these transformations are among the most facile hexatriene electrocyclizations reported thus far.     

Flow-injection method for the determination of serine using immobilized enzyme

A flow-injection method for the determination of serine using a mini-column containing immobilized serine dehydratase isolated and purified from rat liver is described. Ammonia produced from the enzymatic reaction is coupled with hypochlorite and phenol in an alkaline medium yields a blue product due to the indophenol anion formation, which is the basis of a spectrophotometric detection at 640 nm. The limit of detection (2×blank noise) is 0.01 mM with a sample throughput of 25 h⁻¹. Calibration graph is linear in the range 0.2–1.0 mM, with relative standard deviation 0.6–1.0%.     

Determination of arsenic(V) in freshwaters by flow injection with luminol chemiluminescence detection

A simple and rapid flow injection (FI) method is reported for the determination of arsenic(V) based on luminol chemiluminescence (CL) detection. The molybdoarsenic heteropoly acid formed by arsenic and ammonium molybdate in the presence of ammonium vanadate in acidic conditions generated chemiluminescence emission via the oxidation of luminol. The limit of detection was 0.15 μg L^?1, with a sample throughput 120 h^?1. A linear calibration graph was obtained over the range 0.15 to 7.5 μg L^?1 (r ² = 0.9989; n = 9) with relative standard deviation (n = 4) in the range 0.8 to 2.5%. Interfering cations were removed by passing the sample through an in-line iminodiacetate chelating column and phosphate (at 0.6 mg L^?1) was removed off-line by magnesium-induced coprecipitation (MAGIC) method. The method was applied to freshwater samples and the results obtained were in reasonable agreement with the results obtained using HGAAS as the reference method.     

C4−H alkoxylation of 6-bromoindole and its application to the synthesis of breitfussin B

Subjecting 6-bromoindole to an iridium-catalysed triborylation-diprotodeborylation sequence followed by Chan-Evans-Lam coupling gives 6-bromo-4-methoxyindole in good overall yield. This indole C4?H alkoxylation process was used in a formal synthesis of the natural product breitfussin B.