Direct Synthesis of Tri-/Difluoromethyl Ketones from Carboxylic Acids by Cross-Coupling with Acyloxyphosphonium Ions

A simple and straightforward approach to the synthesis of trifluoromethyl and difluoromethyl ketones from widely available carboxylic acids is disclosed. The transformation utilizes an acyloxyphosphonium ion as the active electrophile, conveniently generated in situ from the carboxylic acid substrate by using commodity chemicals. The utility of the reaction system is exemplified by its chemoselectivity, with tolerance to a variety of important functional groups. The late-stage functionalization of carboxylic acid active pharmaceutical ingredients and pharmaceutically relevant compounds is also discussed.     

Biodegradation of the (aliphatic + aromatic) fraction of Oural crude oil. Biomarker identification using GC/MS SIM and GC/MS/MS

A simplified fraction of the Oural crude oil (aliphatic and aromatic hydrocarbons) was incubated in the presence of an hydrocarbonoclastic bacterial community isolated from a marine sediment highly contaminated by petroleum residue. The biodegradation has been carried out under aerobic conditions for 5 weeks and followed by FTIR, UV synchronous luminescence and GC/FID. Disappearance of the n-alkanes (2nd week), an important attack of the isopreno?d compounds (5th week) and preferential alteration of monomethylated polyaromatics were observed. Concerning the biomarkers, the bicyclic alkanes and pentacyclic terpanes have been comparatively elucidated using GC/MS data. The identification of C(26) to C(29) steranes has required a most selective method, namely GC/MS/MS. Many molecular ratios based on GC/MS abundances were calculated, which showed good stability. Consequently, they can be used to determine the origin of a petroleum even one altered by biodegradation.     

Rapid method for simultaneous determination of ascorbic acid and zinc in effervescent tablets by capillary zone electrophoresis with contactless conductivity detection

Ascorbic acid and zinc are essential nutrients that play important roles in nutrition, immune support, and maintenance of health. For this reason, both compounds are widely used as ingredients in dietary supplements. We report, for the first time, an analytical method for fast simultaneous determination of ascorbic acid and zinc. A single analysis run is possible every 80 s (45 injections/h). The method is based on capillary electrophoresis with capacitively coupled contactless conductivity detection using a fused silica capillary with 50 cm length (effective length of 10 cm). The separation was achieved by using a background electrolyte composed by 30 mmol/L of 2‐(morpholin‐4‐yl)ethane‐1‐sulfonic acid and 30 mmol/L of histidine, pH 6.1. The detection limits were 10 and 20 μmol/L and recovery values for spiked samples were 101 and 100% for zinc and ascorbic acid, respectively. The results obtained with the developed procedure were compared to those obtained by titration (ascorbic acid) and flame atomic absorption spectroscopy (zinc), and no statistically significant differences were observed (95% confidence level).     

Amperometric determination of the insecticide fipronil using batch injection analysis: comparison between unmodified and carbon-nanotube-modified electrodes

The electrochemical oxidation of fipronil is investigated on unmodified and multi-walled carbon-nanotube (MWCNT)-modified glassy carbon electrodes (GCEs), and its amperometric determination using batch injection analysis (BIA) is demonstrated. An oxidation peak was observed at 1.5 V in a 0.1 mol L^?1 HClO₄/acetone solution (50:50, v/v) on both surfaces. Although MWCNT-modified GCE provided greater sensitivity, the unmodified GCE showed low RSD value, wider linear range, and reduced adsorption of fipronil or its oxidized products on the electrode surface. A detection limit of 4.7 μmol L^?1 and linear range of 25–300 μmol L^?1 were obtained using a bare GCE. The method was applied in veterinary formulations with results in agreement with those obtained by high-performance liquid chromatography.     

ChemInform Abstract: Structural Properties and Singular Phase Transitions of Metallic Pr0.50Sr0.50CoO3 Cobaltite.

Two successive magnetic transitions of Pr_0.50Sr_0.50CoO₃ contrast with the single ferromagnetic transition in other Ln_0.50Sr_0.50CoO₃ compounds.     

Correction to: Thermodynamic model and Raman spectra of MgO–P2O5 glasses

Journal of Thermal Analysis and Calorimetry - Convection heat transfer in cavities has attracted much attention from researchers. Many kinds of nanofluids have exhibited non-Newtonian behavior and...     

A new method for the study of processes at the liquid-liquid interface using an array of microdroplets on a au electrode.

We report the fabrication of partially blocked gold electrodes, with regularly and hexagonally spaced inert hydrophobic blocks on their surface. The hydrophobic blocks, with diameters of 5 mum, are used to support liquid 5-nonyl-salicylaldoxime (Acorga-P50) droplets on the surface. By voltametrically monitoring the transport-controlled reduction rate of Cu(II) (in pH 5 solution) at the unblocked part of the gold surface it is possible to deduce, via simulation, the parameters controlling the rate of uptake of Cu(II) at the droplet-aqueous solution interface as the droplet "fills up" with Cu(II). Experimentally, it is recorded that the reduction current increases until the droplet is filled completely; after this, there is no further noticeable effect of the droplet coating. A rigorous theoretical analysis of the transients permits the deduction of partition coefficients between the aqueous solution and the organic-droplet phase and of diffusion coefficients within the droplet. The partition coefficient for Cu(II) between water and 5-nonyl-salicylaldoxime was found to be 200 at 25 degrees C and the diffusion coefficient of Cu(II) inside the organic phase was determined to be 5 x 10(-11) cm2 s(-1).     

AN EQUILIBRIUM BETWEEN SPIROPHOSPHORANIC AND TETRACOORDINATED PHOSPHORUS COMPOUNDS HAVING THE PHOSPHORUS-BORON BOND

Abstract

A new adduct was isolated from the reaction of borane-dimethyl-sulfide complex and conjugate bases of spirophosphorane prepared from benzilic acid. In solution, it exists as equilibrium between a spirophosphorane and a tetracoordinated phosphorus compound bearing a phosphorus-boron bond.