Synthesis of unsaturated polyester resins for large sized composites

A series of unsaturated polyesters based on phthalic anhydride (PHA), maleic anhydride (MA), ethylene glycol (EG), diethylene glycol (DG), triethylene glycol (TG), propylene glycol (PG), styrene (Sty) and acrylonitrile (AN) were prepared. The molecular weights of the prepared polyesters were determined by end-group analysis. The effect of the structure of the resin on its curing behavior has been investigated. On the basis of the experimental study, the following were concluded: (1) The maximum curing temperature (T_max) is related to the molecular weight of the glycol incorporated in these castings. In this context the T_max was found to decrease with increasing the molecular weight. Meanwhile the time to peak temperature t_max was increasing. (2) The higher the percentage of AN in the crosslinking monomer system, the slower a resin cures. (3) The values of T_max were found to be influenced to a large extent by the percentage of AN.     

Thermal reaction of clCH2CONH2 in molten acetamide

Mixtures composed of amides and electrolytes exhibit interesting properties such as viscoelastic behaviour and a megavalue of the dielectric constant. In order to improve the dielectric properties, the authors are investigating a large number of molten mixtures of CF₃COONa with different types of amides, including the ternary system sodium trifluoroacetate-chloroacetamide-acetamide. The experimental measurements showed that the ternary mixtures are thermally unstable. A yellow oily product is formed; this was purified and tested by means of IR and NMR techniques. The formula and the kinetic mechanism are proposed.     

Volumetric determination of Pt(IV) in the presence of Ir,Pd, and Rh with ferrous ammonium sulfate in alkaline mannitol medium

A potentiometric reductimetric method for the determination of platinum (Pt(IV)Pt(II)) with a standard Fe(II) solution in an alkaline medium of mannitol is described. The method, the error of which does not exceed 2%, can be used in the presence of palladium, iridium, and rhodium.     

Stereospecific synthesis of 1,2-cis glycosides by vinyl-mediated IAD

[reaction: see text] Stereospecific 1,2-cis glycosylation of 2-O-vinyl thioglycosides, synthesized from the corresponding alcohols by Ir-catalyzed transvinylation with vinyl acetate, is achieved by iodine-mediated tethering of a range of primary and secondary carbohydrate acceptors, followed by intramolecular aglycon delivery (IAD). The use of such an intramolecular glycosylation strategy furnishes the desired alpha-gluco and beta-manno disaccharides in an entirely stereoselective manner.     

Semiquantitative determination of thiourea,thiocyanate, and sulfide by circular thin layer chromatography

Summary A method for semiquantitative determination of thiourea, thiocyanate, and sulfide is described. It involves making circular spots or rings on chromatoplates using the circular thin layer Chromatographic apparatus. The method is based on sensitivity and specificity of spot reactions and comparison of the color intensity of a circular spot with that of sensitivity standards. The accuracy of the method is ± 5% and the procedure is rapid, simple and economical.

---

Zusammenfassung Ein Verfahren zur halbquantitativen Bestimmung von Thioharnstoff, Thiocyanat und Sulfid wurde beschrieben. Es beruht auf der chromatographischen Herstellung kreisförmiger Flecken oder Ringe auf Dünnschichtplatten. Mit empfindlichen und spezifischen Tüpfelreaktionen wurden die Flecken gefärbt und die Farbintensität mit Standardproben verglichen. Die Genauigkeit beträgt ± 5%.

     

Understanding the dehydrogenation mechanism over iron nanoparticles catalysts based on density functional theory

The conversion of chemical feedstock materials into high value-added products accompanied with dehydrogenation is of great value in the chemical industry.However,the catalytic dehydrogenation reaction is inhibited by a limited number of expensive noble metal catalysts and lacks understanding of dehydrogenation mechanism.Here,we report the use of heterogeneous non-noble metal iron nanoparticles(NPs) incorporated mesoporous nitrogen-doped carbon to investigate the dehydrogenation mechanism based on experiment observation and density functional theory(DFT) method.Fe NPs catalyst displays excellent performance in the dehydrogenation of 1,2,3,4-tetrahydroquinoline(THQ)with 100% selectivity and 100% conversion for 10-12 h at room temperature.The calculated adsorption energy implies that THQ prefers to adsorb on Fe NPs as compared with absence of Fe NPs.What is more,the energy barrier of transition state is relatively low,illustrating the dehydrogenation is feasible.This work provides an atomic scale mechanism guidance for the catalytic dehydrogenation reaction and points out the direction for the design of new catalysts.     

Solvent- and metal-free selective oxidation of thiols to disulfides using I2/DMSO catalytic system

We describe herein a simple, fast and inexpensive protocol for the oxidative coupling of thiols employing a stoichiometric amount of DMSO and iodine as the catalyst. Various aromatic disulfides were obtained in good to excellent yields in short reaction times at room temperature, while aliphatic disulfides were achieved in good yields when the reactions were conducted under microwave irradiation.     

Spectroscopic and morphological study of laser ablated Titanium

The optical characteristics of biological tissues sampled from the anterior abdominal wall of laboratory rats are for the first time experimentally studied in a wide wavelength range (350-2500 nm). The experiments have been performed in vitro using a LAMBDA 950 (PerkinElmer, United States) spectrophotometer. Inverse Monte Carlo simulation is used to restore the spectral dependences for scattering and absorption coefficients, as well as the scattering anisotropy factor for biological tissue based on the recorded spectra of diffuse reflection and total and collimated transmissions.     

4-hydroxy-2H-1,2-benzothiazine-3-carbohydrazide 1,1-dioxide-oxalohydrazide (1:1): X-ray structure and DFT calculations

The title compound, 4-hydroxy-2H-1,2-benzothiazine-3-carbohydrazide 1,1-dioxide-oxalohydrazide (1:1), is determined using X-ray diffraction techniques and the molecular structure is also optimized at the B3LYP/6-31G(d,p) level using density functional theory (DFT). The asymmetric unit consists of four independent molecules. The oxalohydrazide molecules have the centre of symmetry at the mid-point of the central C-C bond. Each thiazine ring adopts a half-chair conformation. Intermolecular C-H...O, N-H...O and N-H...N hydrogen bonds produce R ₂ ² (10), R ₂ ² (13), R ₃ ³ (12) and R ₃ ³ (15) rings, which lead to one-dimensional polymeric chains. An extensive three-dimensional supramolecular network of N-H...N, N-H...O, C-H...O and O-H...O hydrogen bonds is responsible for crystal structure stabilization.