A critical review on photochemical conversions in flow analysis

Photochemical conversions are cost-effective and environmental friendly processes that require mild experimental conditions and avoid generation of highly acidic wastes. Treated samples are then compatible with most of the analytical techniques. These characteristics become more relevant when the photoconversions are accomplished to flow analysis, thus allowing exploitation of incomplete reactions, the effective use of the photogenerated unstable radicals and in-line sample treatment. Decreasing of reagent consumption and waste generation, sample processing in a closed environment, and improvement of efficiency of the photochemical processes are other inherent advantages. These aspects are critically reviewed in this article, which emphasizes applications to fractionation and speciation analysis, photo-induced luminescence, miniaturization, and in-line waste treatment. Design of flow-through photochemical cells, use of auxiliary reagents in homogeneous and heterogeneous media, and configurations of flow manifolds are also discussed.     

Comparative study of the vicinal functionalization of olefins with 2:1 bromide/bromate and iodide/iodate reagents

A comparative evaluation was made on the syntheses of vicinal halohydrins, halo methyl ethers, and halo acetates from olefins using 2:1 Br⁻/BrO₃⁻ and I⁻/IO₃⁻ reagents. In many cases both reagents afforded products selectively in high yields. The highest halogen atom efficiencies attained were 97% and 93% for Br⁻/BrO₃⁻ and I⁻/IO₃⁻, respectively. Of the two reagents, I⁻/IO₃⁻ was established to be the preferred reagent for vicinal functionalization of linear alkenes and also for halo acetate preparation. However, only Br⁻/BrO₃⁻ was effective for vicinal functionalization of trans-stilbene and chalcones.     

Configuration of a Naphtho[2,3-B]thiophene-diels-Alder Adduct from Shift Reagent Data

Since Hinckley's discovery¹, that lanthanide-complexes are useful tools in resolving complex NMR-spectra, this method has been widely used. Especially the work of Williams² has contributed materially to the application of this technique in organic chemistry. In this paper, the Eu(DPM)₃-complex was used to determine the configuration of a naphtho[2,3-b]thiophene-Diels-Alder adduct.     

新显色剂二溴对氯偶氮磺磺的合成及其与Ce(Ⅲ)的显色反应

合成了一种新的显色剂二溴对氯偶氮磺磺 ,该显色剂对 Ce( )具有很好的显色反应 ,且有较好的选择性。可用于稀土矿石中的 Ce( )分光光度分析。     

C[sbnd]C Asymmetric Bond Formation Mediated by Optically Active Sulfoxides

Abstract

Highly stereoselective C[sbnd]C bond forming reactions can be performed with a variety of optically active sulfinyl derivatives to afford, after desulfurization, optically active sulfur-free products.     

Reactivite Des N 1 -Tosylamidrazones Vis-À-Vis du Chlorure de Thionyle et du Reactif de Lawesson: Obtention Des Thiatriazoles et Des Triazaphospholines

Thionyl chloride 2 and Lawesson Reagent (L.R.) 4 react with N 1 -tosylamidrazones 1 to give respectively 1-oxyde-1,2,3,5-thiatriazole 3 and triazaphospholines 5 derivatives. The structure of products 3 and 5 is confirmed by IR and NMR spectroscopy.     

A Modified Method using TRIzol® Reagent and Liquid Nitrogen Produces High-Quality RNA from Rat Pancreas

To establish an economical and reproducible method for the high-quality RNA extraction from pancreas, we isolated total RNA from rat pancreas with TRIzol reagent and liquid nitrogen. In the initial stage, we optimized three influential factors, the way to homogenize pancreas, the time to collect the pancreatic tissue from animals, and the weight of the pancreatic tissue in 1 ml of TRIzol reagent. The RNA quality was determined by detecting total RNA content and its absorbance at 260/280 nm wavelength, visualizing RNA in non-denatured agarose gel and performing RT-PCR of pancreas-specific genes. The A (260)/A (280) ratio of the total RNA extracted by grinding 20-30 mg of rat pancreatic tissue removed from the rats in liquid nitrogen within 1 min and then immersed in 1 ml of the TRIzol Reagent was 1.75-1.89, and the ratio of 28S/18S ribosomal RNA bands was more than 1.8. Furthermore, full length of Pdx1 open-reading frame was amplified with RNA extracted from the grinding group rather than from the conventional group. The RT-PCR products of pancreas-specific genes from both exocrine and endocrine parts of pancreas were successfully derived from the extracted RNA. The results suggested that we successfully provided an economical, fast, and reproducible method to obtain the high-quality and intact RNA from rat pancreas with TRIzol Reagent and liquid nitrogen.     

Reactions of 1,1,2,2-tetrafluoroethyl-N,N-dimethylamine with linear and cyclic 1,3-diketones

Ketones are known to be unreactive toward α-fluoroamines such as Ishikawa's Reagent or 1,1,2,2-tetrafluoroethyl-N,N-dimethylamine (TFEDMA). On the other hand, 1,3-diketones were found to undergo fluorination with TFEDMA. In the case of linear 1,3-diketones, the proposed mechanism involves the formation of β-fluoro-α,β-unsaturated ketones followed by the addition of HF to selectively give the product β,β-difluoroketone. Interestingly, when the 1,3-diketone is cyclic (i.e. 1,3-cyclohexadione) the outcome of the reaction is different and results in the formation of a product with a 2,2-difluoroacetyl group on the 2-carbon.     

Photometrische Rheniumbestimmung in industriellen Proben. Eine schnelle und einfache Methode mit hoher Selektivität

Summary Malachite green reacts with rhenium(VII) to produce a green 1:1-compound which has a maximum of absorption at =630 nm. The system in benzene obeys Lambert-Beer's law from 0.4 to 40 ppm Re(VII). The composition of the extracted complex was determined by Job's method. The influence of interfering ions on the method was examined. Benzene was substituted by different organic solvents. The method was used for rhenium determination in a new hydrodesulfurization catalyst [1].