Synthesis of Isothiocyanates Using DMT/NMM/TsO− as a New Desulfurization Reagent

Thirty-three alkyl and aryl isothiocyanates, as well as isothiocyanate derivatives from esters of coded amino acids and from esters of unnatural amino acids (6-aminocaproic, 4-(aminomethyl)benzoic, and tranexamic acids), were synthesized with satisfactory or very good yields (25–97%). Synthesis was performed in a “one-pot”, two-step procedure, in the presence of organic base (Et₃N, DBU or NMM), and carbon disulfide via dithiocarbamates, with 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium toluene-4-sulfonate (DMT/NMM/TsO⁻) as a desulfurization reagent. For the synthesis of aliphatic and aromatic isothiocyanates, reactions were carried out in a microwave reactor, and selected alkyl isothiocyanates were also synthesized in aqueous medium with high yields (72–96%). Isothiocyanate derivatives of L- and D-amino acid methyl esters were synthesized, under conditions without microwave radiation assistance, with low racemization (er 99 > 1), and their absolute configuration was confirmed by circular dichroism. Isothiocyanate derivatives of natural and unnatural amino acids were evaluated for antibacterial activity on E. coli and S. aureus bacterial strains, where the most active was ITC 9e.     

O-Trimethylsilylenol ethers as versatile building blocks in a modular preparation of polyenic backbone

Versatility and synthetic potential of 1-(trimethylsilyloxy)-1,3-butadiene, 1-(trimethylsilyloxy)penta-1,3-diene, and their methyl substituted derivatives have been demonstrated in a modular synthetic methodology of stereodefined π-conjugated unsymmetrical, symmetrical two-dimensional, and octupolar polyenal structure.     

Indirect Speciation Analysis of Thallium in Plant Extracts by Anodic Stripping Voltammetry

A sensitive voltammetric method (DPASV) was developed for the determination of Tl(I) and Tl(III) in plant extracts. To limit the influence of the organic matrix on the measurements, UV irradiation and addition of Amberlite XAD‐7 resin was studied. The application of 0.5 g of the resin allowed defining thallium speciation in 10.0 mL of a solution containing 0.20 mL of Sinapis alba extract. The quantification limit of 0.5 ng mL^?1 Tl(I) was found for only 10 min of preconcentration, and is low enough to allow dilution of the sample before thallium determination. The procedure was validated using the recovery study and intermethod comparison with HPLC ICP MS.     

β-( N -Acylamino)vinylphosphonium Salts--Synthesis and Properties

A reaction of g -carbonyl phosphorus ylides with imidoyl halides gives hitherto unknown g -( N -acylamino)vinylphosphonium salts. The same product can be obtained using the N-monosubtituted amide/Ph 3 PBr 2 /Et 3 N system instead of imidoyl halide. The key step of the reaction probably involves an intramolecular [1,3] O-to-N migration of the vinyl group, converting the primary O -imidoylation product into g -( N -acylamino)vinylphosphonium salt.     

Mid‐ and Near‐Infrared Spectroscopic Determination of Carbon in a Diverse Set of Soils from the Brazilian National Soil Collection

Abstract

Calibrations for soil carbon content measured by combustion (total carbon, TC) and chromate oxidation by a modified Walkley‐Black method (Walkley‐Black carbon, WBC) from the Brazilian National Soil Collection were made using Fourier‐transform near (1100 to 2500 nm; NIRS) and mid‐infrared diffuse reflectance (2,500 to 25,000 nm; DRIFTS) spectroscopy combined with partial least squares (PLS). Calibration sets of sample populations of different carbon ranges, soil taxonomic classes, and soil textural groups were established. These are for TC ranges between 0.4 to 555.0, 0.4 to 99.1, and 0.4 to 39.9 g kg^?1: for WBC 0.2 to 401.0, 0.2 to 66.0, and 0.2 to 66.0, and 0.2 to 30.0 g kg^?1: for soil taxonomic classes Ferralsols and Acrisols; and for soil textural groups very clayey, clayey, and medium textures were examined. Calibrations obtained for the largest TC and WBC ranges were better compared to the lower ones, but lower root mean squared deviation (RMSD) and relative difference (RD=RMSD/mean value) were found for the lower carbon ranges. Taxonomic soil class was not an adequate criterium for calibration set formation. Soil texture had effect on calibrations, especially using NIR, because of the particle size effect to which NIR was more sensitive than mid‐IR. In general, DRIFTS showed better performance than NIRS. NIRS only outperformed DRIFTS when used with calibration set fairly homogeneous in its particle size distribution. Results demonstrated that while calibrations can be developed using either DRIFTS or NIRS for even a very diverse set of soil samples, which will determine C over a wide range of concentrations inherent in such a diverse set, it is desirable to seperate sample populations by soil textural properties and choose the adequate spectral range (NIR or mid‐IR) based on the textural group, for calibration development to achieve more accurate results.     

Synthesis of Chiral 2,4-Chiral 2,4-Dichloro-6-menthoxy-1,3,5-triazines and 2-Chloro-4, 6-Dimenthoxy-1,3,5-triazines as Enantiodifferentiating Coupling Reagents. An X-ray Study on 2,4,6-Trimenthoxy-1,3,5-triazine

Chiral mono-di-and trimenthoxy-1,3,5-triazines ware obtained from natural menthol and cyanuric chloride and applied as enantioselective coupling reagents in the synthesis of dipeptides.     

Determination of trace elements in suspensions and filtrates of drinking and surface water by wavelength-dispersive X-ray fluorescence spectrometry

An X-ray fluorescence method (XRF) is presented that allowed low detection limits (at the 0.1–23 ng mL⁻¹ level) to be obtained for Cr, Mn, Fe, Ni, Zn, Sr, Pb, Bi and Br in water. The samples were prepared using a thin layer method. Trace elements were determined via the calibration curve and standard addition. Absorption effects and inhomogenities in prepared samples were checked for using the emission–transmission method and internal standards, respectively. The results from the XRF method were compared with the results from the inductively coupled plasma atomic emission spectrometry method.      

Microorganisms in inorganic chemical analysis

There are innumerable strains of microbes (bacteria, yeast and fungi) that degrade or transform chemicals and compounds into simpler, safer or less toxic substances. These bioprocesses have been used for centuries in the treatment of municipal wastes, in wine, cheese and bread making, and in bioleaching and metal recovery processes. Recent literature shows that microorganisms can be also used as effective sorbents for solid phase extraction procedures. This review reveals that fundamental nonanalytical studies on the parameters and conditions of biosorption processes and on metal–biomass interactions often result in efficient analytical procedures and biotechnological applications. Some selected examples illustrate the latest developments in the biosorption of metals by microbial biomass, which have opened the door to the application of microorganisms to analyte preconcentration, matrix separation and speciation analysis.     

Flammability Tests and Investigations of Properties of Lignin-Containing Polymer Composites Based on Acrylates

In this paper flammability tests and detailed investigations of lignin-containing polymer composites’ properties are presented. Composites were obtained using bisphenol A glycerolate (1 glycerol/phenol) diacrylate (BPA.GDA), ethylene glycol dimethacrylate (EGDMA), and kraft lignin (lignin alkali, L) during UV curing. In order to evaluate the influence of lignin modification and the addition of flame retardant compounds on the thermal resistance of the obtained biocomposites, flammability tests have been conducted. After the modification with phosphoric acid (V) lignin, as well as diethyl vinylphosphonate, were used as flame retardant additives. The changes in the chemical structures (ATR-FTIR), as well as the influence of the different additives on the hardness, thermal (TG) and mechanical properties were discussed in detail. The samples after the flammability test were also studied to assess their thermal destruction.