Iodine monochloride in anhydrous acetic acid as an oxidizing agent

A systematic study of the redox reactions of iodine monochloride with various inorganic ions in glacial acetic acid medium is described. Sodium sulphite, mercury(I) perchlorate, antimony trichloride, arsenic trichloride and iron(II) perchlorate were examined. Potentiometric and amperometric methods were used to follow the reduction of iodine monochloride, which yields different products according to the type of reductant.     

Paramagnetic nitrosyliron adducts in pentasilic zeolites: an EPR study

The interaction of nitrogen monoxide with various types of iron-containing pentasilic zeolites has been investigated by EPR spectroscopy. The systems investigated were iron-silicalite, ion-exchanged ZSM-5 and a bare silicalite impregnated with iron ions at the external surface only. NO forms paramagnetic adducts on all these systems essentially reacting with Fe(II) species. Three distinct types of nytrosyl adducts have been identified all lacking the hyperfine structure. Two of them are in doublet (S=1/2) state while the third one, observed in ZSM-5 samples only and already reported in the literature, is a quadruplet (S=3/2). While all activated samples exhibit EPR spectra (due to Fe(III) ions) very similar one to each other, their reactivity towards NO is different in each case. This allows some advance in understanding the state of the activated samples which, due to the high importance of iron-containing pentasilic zeolites in heterogeneous catalysis, is the object of a active debate in the literature.     

Deposition of SiOx Films from Hexamethyldisiloxane/Oxygen Radiofrequency Glow Discharges: Process Optimization by Plasma Diagnostics

Optical emission and Fourier transform infrared absorption diagnostics have been carried out in hexamethyldisiloxane/oxygen RF discharges for studying the effects of the feed composition and the power on the deposition of SiO₂—like thin films. Ex situ FTIR absorption has been utilized to monitor organic moieties and silanol groups in the film. It is shown that carbon-free films can be obtained by highly diluting the monomer in oxygen, while medium-to-high power is necessary to abate silanol groups. These two conditions represent the optimization criterion to obtain excellent barrier films for food packaging applications.     

Liquid chromatography-mass spectrometry in occupational toxicology: a novel approach to the study of biotransformation of industrial chemicals

Biological monitoring and biomarkers are used in occupational toxicology for a more accurate risk assessment of occupationally exposed people. Appropriate and validated biomarkers of internal dose, like urinary metabolites, besides to be positively correlated with external exposure, have a predictive value to the risk of adverse effects. The application of liquid chromatography-mass spectrometry (LC-MS) in occupational and environmental toxicology, although relatively recent, has been demonstrated valid in the determination of traditional biomarkers of exposure, as well as in metabolism studies aimed at investigating minor metabolic routes and new more specific biomarkers. This review presents selected applications of LC-MS to the study of the metabolism of industrial chemicals, like n-hexane, benzene and other aromatic hydrocarbons, styrene and other monomers employed in plastic industry, as well as to other chemicals used in working environments, like pesticides used by farmers, and antineoplastic agents prepared by hospital personnel. Analytical and pre-analytical factors, which affect quantitative determination of urinary metabolites, i.e. sample preparation, matrix effect, ion suppression, use of internal standards, and calibration, are emphasized.     

Blue silver: a very sensitive colloidal Coomassie G-250 staining for proteome analysis

A modified Neuhoff's colloidal Coomassie Blue G-250 stain is reported, dubbed "blue silver" on account of its considerably higher sensitivity, approaching the one of conventional silver staining. The main modifications, as compared to Neuhoff's protocol, were: a 20% increment in dye concentration (from 0.1% up to 0.12%) and a much higher level of phosphoric acid in the recipe (from 2% up to 10%). The "blue silver" exhibits a much faster dye uptake (80% during the first hour of coloration, vs. none with a commercial preparation from Sigma). Even at equilibrium (24 h staining), the "blue silver" exhibits a much higher sensitivity than all other recipes, approaching (but lower than) the one of the classical silver stain. Measurements of stain sensitivity after sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of bovine serum albumin (BSA) gave a detection limit (signal-to-noise ratio > 3) of 1 ng in a single zone. The somewhat lower sensitivity of "blue silver" as compared to classical silvering protocols in the presence of aldehydes is amply compensated for by its full compatibility with mass spectrometry of eluted polypeptide chains, after a two-dimensional map analysis, thus confirming that no dye is covalently bound (or permanently modifies) to any residue in the proteinaceous material. It is believed that the higher level of phosphoric acid in the recipe, thus its lower final pH, helps in protonating the last dissociated residues of Asp and Glu in the polypeptide coils, thus greatly favoring ionic anchoring of dye molecules to the protein moiety. Such a binding, though, must be followed by considerable hydrophobic association with the aromatic and hydrophobic residues along the polypeptide backbone.     

5-Phenylthio-1,3-oxazinan-4-ones via hetero Diels–Alder reactions: synthesis of (R)- and (S)-Duloxetines and Fluoxetines

The synthesis of 5-phenylthio-1,3-oxazinan-4-ones, through a hetero Diels–Alder strategy, is described. The cycloadducts thus prepared have been shown to be useful intermediates for the synthesis of 1,3-aminoalcohols, valuable intermediates in the preparation of biologically significant molecules, e.g., optically active Duloxetines and Fluoxetines. In the course of this elaboration a novel microwave assisted desulfurization reaction is reported.     

Synthesis of Fluorinated Bent‐Core Mesogens (BCMs) Containing the 1,2,4‐Oxadiazole Ring

New fluorinated bent‐core mesogens containing the 1,2,4‐oxadiazole or 1,2,4‐triazole nucleus have been synthesized taking advantage of the ANRORC ( A ddition of N ucleophile, R ing‐ O pening, R ing‐ C losure) reactivity of 5‐perfluoroalkyl‐1,2,4‐oxadiazoles. Physical state changes of the obtained compounds were characterized through DSC, POM, and SAXS. Besides the formation of a smectic mesophase, a novel behavior as organic molecular glass was evidenced for some 1,2,4‐oxadiazole derivatives.     

Identifying Sn Site Heterogeneities Prevalent Among Sn‐Beta Zeolites

In recent years, various protocols on preparing Lewis acidic Sn‐β zeolite hydrothermally and postsynthetically have been reported. However, very little is known about the effects of different synthesis protocols on the Sn(IV) speciation in the final material. Even the effects of individual synthesis parameters within a certain preparation method have not been studied systematically. Here, we demonstrate that hydrothermally synthesized Sn‐β zeolites prepared via very similar recipes show significantly different ¹¹⁹Sn‐NMR spectra, suggesting different Sn site speciation. Among postsynthetically prepared Sn‐β zeolites, less variation in the resulting ¹¹⁹Sn‐NMR spectra have been observed, indicating a more reproducible synthesis procedure compared to hydrothermal synthesis in fluoride media. This work highlights the importance of ¹¹⁹Sn‐NMR measurements to elucidate the precise local geometry of the Sn heteroatoms in Sn‐β, and the need to quantify the number of reactive Sn sites on each sample that participate in a given catalytic reaction, in order to accurately compare materials prepared by different routes.