A computational investigation on the potential energy surface of thiosulfeno with O(3P) reaction

The reaction paths of thiosulfeno radical (HS₂) with O(³P) have been investigated at the UB3LYP/aug-cc-pV(T + d)Z and UCCSD(T)/aug-cc-pV(T + d)Z//B3LYP levels. Two stable collision intermediates, HSSO and SS(H)O, have been considered for the HS₂ + O(³P) reaction. Four products of S + HSO, H + SSO, HS + SO, and S₂ + OH are obtained by starting from HSSO and SS(H)O. The calculated results show that the most feasible paths for the formation of S + HSO, H + SSO, and HS + SO products include no transition states in reaction path, while that of S₂ + OH product includes relatively high energy barriers of 23.0 kcal/mol. Therefore, S + HSO, H + SSO, and HS + SO are main products (with the stability other of HS + SO > H + SSO > S + HSO) and S₂ + OH is the second product in HS₂ + O(³P) reaction. Because, all intermediates, transition states, and products involved in the reaction paths lie below the initial reactants, the HS₂ + O(³P) reaction is expected to be rapid even at low temperatures.     

Synthesis and Characterization of Carbon-Stabilized Magnesium Nanoparticles

Magnesium nanopowder has attracted many interests in the recent years, which has a very difficult and costly synthesis process because of its high activity. In this work, magnesium nanoparticles stabilized with amorphous carbon (Mg–C nanoparticles) were synthesized by submerged arc discharge technique in kerosene. The arc discharge was generated between two electrodes of magnesium at the arc current of 1 A and arc voltage of 50 V. Mg–C nanoparticles were characterized by various techniques. Dynamic light scattering result indicated that size of magnesium nanoparticles is about 35 nm. X-ray diffraction showed that the produced sample consisted of hexagonal magnesium and amorphous carbon and there was no presence of magnesium oxides in the pattern. Field emission scanning electron microscopy and transmission electron microscopy results illustrated that the sample has morphology of agglomerated nanospheres. Energy dispersive X-ray spectroscopy demonstrated formation of 57 percent magnesium and 43 percent carbon. Differential scanning calorimetry analysis showed that the amorphous carbon increased ignition temperature of nanoparticles by 180 °C compared to pure magnesium micron-sized powder. Therefore, Mg–C nanoparticles can have many applications in different fields similar to magnesium nanopowders. However, by producing Mg–C nanoparticles, there is no need for vacuum chamber or inert gases during production and after that, since amorphous carbon protects magnesium nanoparticles from oxidation.     

Two Reliable Simple Relationships between Flash Points of Hydrocarbon Kerosene Fuels and Their Molecular Structures

This study presents two new reliable simple correlations for predicting flash point of kerosene hydrocarbons using multiple linear regression method. The methodology assumes that the flash point of kerosene fuels can be expressed as a function of elemental composition and several structural parameters. The proposed correlations have determination coefficients of 0.910 and 0.977. Also, the first model has root mean square deviation (RMSD) and the average absolute deviations (AAD) of 10.6 and 8.2 K, respectively, for 111 kerosene fuels with different molecular structures as training set. The RMSD and AAD for the second improved model are 5.39 and 4.33 K, respectively. The predictive power of two correlations is checked using a cross validation method. (R² = 0.977, Q²_Ext = 0.975, and Q²_LMO = 0.979). Also, these correlations give good predictions for further 25 kerosene fuels as test set. The proposed model can also be applied for designing novel kerosene fuels.     

On‐line determination of sarcosine in biological fluids utilizing dummy molecularly imprinted polymers in microextraction by packed sorbent

Several years ago, sarcosine received attention as a prostate‐cancer marker. Prostate cancer is one of the most widespread types of tumor diseases in men. The prostate‐specific antigen is normally used as a marker, and it can only be detected in blood with a sensitivity of approximately 80%. In the present study, dummy molecularly imprinted polymers in microextraction by packed sorbent with on‐line liquid chromatography coupled to tandem mass spectrometry was used for the determination of sarcosine in human plasma and urine samples. The polymer network glycine was used for the dummy molecularly imprinted polymers. The selectivity of the method was evaluated using similar prostate‐cancer biomarkers. In addition, various parameters affecting the extraction performance were investigated. The method limits of detection and quantification in the plasma and urine were 1.0 and 3.0 ng/mL, respectively. The values of the coefficient of determination were over 0.99 for all runs in the studied concentration range (3.0–10 000 ng/mL). The method recovery was 87 and 89% in plasma and urine, respectively. The intraday and interday precisions of sarcosine in the plasma and urine samples were in the ranges of 4.0–7.1, 3.0–6.3, 2.9–4.7, and 5.0–6.7, respectively.     

Activated nitriles in heterocyclic synthesis: Synthesis of 6-thiophen-2-yl and 6-furan-2-ylthiazolo[2,3—a]pyridine derivatives

A variety of new 6-thiophen-2-yl and 6-furan-2-ylthiazolo[2,3—a]pyridine derivatives could be prepared via the reaction of 2-functionally substituted methyl-2-thiazolin-4-one with cyanomethylenethiophen-2-yl and cyanomethylenefuran-2-yl derivatives. The structure of the reaction products was established based on spectral data.

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Aktivierte Nitrile in der Heterocyclen-Synthese: Die Synthese von 6-Thiophen-2-yl-und 6-Furan-2-yl-thiazolo[2,3—a]pyridin-Derivaten

Zusammenfassung Es konnte eine Reihe neuer 6-Thiophen-2-yl- und 6-Furan-2-yl-thiazolo-[2,3—a]pyridine über die Reaktion von 2-funktionell-substituierten Methyl-2-thiazolin-4-onen mit Cyanomethylenthiphen-2-yl bzw. Cyanomethylenfuran-2-yl-Derivaten hergestellt werden. Die Struktur der Reaktionsprodukte wurde mit spektroskopischen Methoden ermittelt.

     

The Tetraphenylester of the μ-Imido-Dithiodiphosphoric Acid and its palladium complex — crystal structures

The preparations of [(C₆H₅O)₂PS]₂NH ( SS ) and its Pd complex [Pd{C₆H₅O₂P(S)NP(S)(OC₆H₅) ₂}₂] ( PDSS ) are described. The compounds were characterized by elemental analysis, NMR, and mass spectra and X-ray structure analysis. The structure of SS contains two independent molecules in an asymmetric unit which are joined into dimers via N …? H …? S hydrogen bonds. SS is a Br?nsted acid And reacts with Pd^II to a neutral chelate complex. The structure of PDSS is composed of isolated molecules with Pd atom in the center of symmetry. The Pd atom is coordinated by 4 S atoms in a distorted square-planar arrangement with average distance Pd? S 2.345(6) Å and an angle S? Pd? S 98.29(4)°.     

Simultaneous spectrophotometric determination of Sn(II) and Sn(IV) by mean centering of ratio kinetic profiles and partial least squares methods

Two spectrophotometric methods are described for the simultaneous determination of binary mixtures of Sn(II) and Sn(IV) in water samples and fruit juice samples, without prior separation steps, using the mean centering of ratio kinetic profiles and partial least squares (PLS) methods. The methods are based on the difference in the rate of the reactions of Sn(II) and Sn(IV) with pyrocatechol violet at pH 4.0. The methods allow rapid and accurate determination of Sn(II) and Sn(IV). The analytical characteristics of the methods for the simultaneous determination of binary mixtures of Sn(II) and Sn(IV) were calculated. The results showed that the methods were capable to simultaneous determination of 0.1–1.80 mg L⁻¹ each of cations. The proposed methods were successfully applied to the simultaneous determination of Sn(II) and Sn(IV)in an orange juice sample.     

Comparison of novel pyridine-functionalized mesoporous silicas for Au(III) extraction from natural samples

A technique for solid-phase extraction utilizing pyridine-functionalized nanoporous silica (MCM-41, MCM-48 and SBA-15) was developed for the determination of gold in different samples using flame atomic absorption spectrometry. The effects of concentration and volume of eluent, pH of the solution, flow rate of extraction, sample volume and of potentially interfering ions on the efficiency of preconcentration and recovery was investigated. The limit of detection is lower than 45 pg mL^?1. Under optimal conditions, the accuracy and precision (RSD%) of the method were calculated to be >99.5% and <0.7% for the two MCMs (41 and 48) and >89.5%, and <1.5% for SBA-15, respectively. The SPE technique was used to determine the concentration of gold in natural and industrial wastewater with satisfactory results.

A computational study of the non-covalent bindings in complexes pairing sulfur tetroxide (SO4(C2V)) with the nitrous oxide (NNO)

The computational investigations are carried out on heterodimers containing sulfur tetroxide (SO₄(C_2V)) with the nitrous oxide (NNO) through MP2/cc–pVDZ and MP2/aug–cc–pVTZ//MP2/cc–pVDZ levels. Eight heterodimers are located on the potential energy surface of SO₄(C_2V)–NNO system. Binding energies of heterodimers in the SO₄(C_2V)–NNO system corrected with BSSE and ZPE are in the range of 1.17–7.90 kJ/mol. The calculated results reveal that the individual interaction of NNO terminal nitrogen atom with one of oxygen atoms of OSO ring in the SO₄(C_2V) monomer leads to the formation of the more stable heterodimer of SO₄(C_2V)–NNO system. The atoms in molecules theory were applied to analyze the nature of intermolecular interactions.     

Insight into detailed mechanism of the atmospheric reaction of imidogen with hydroxyl: a computational study

The details of reaction mechanism of imidogen (NH) and hydroxyl radicals are explored at the UMP2(FC)/cc–pVDZ and PMP4(FC,SDTQ)/cc–pVQZ//UMP2 + ZPE levels, theoretically. The initial association between NH and OH radicals leads to the formation of the intermediates, NH…OH, HN…HO, cis HNOH, and trans HNOH, through the barrierless and exothermic processes. By starting from the initial intermediates, all possible paths for the formation of H + HNO, H₂ + NO, H₂O + ⁴N, H₂N + ³O, and H + ³HON products are investigated on potential energy surface. The results reveal that H₂O + ⁴N is the main product involved in the mechanism of hydrogen atom abstraction of NH by OH radical through the intermediate NH…OH.