Synthesis and Spectroscopic Study of Some New Phosphoramidates,Crystal Structures of N‐Benzoyl‐N′,N″‐bis(azetidinyl)phosphoric Triamide and N‐Benzoyl‐N′,N″‐bis(hexamethylenyl)phosphoric Triamide

Some new N‐carbonyl, phosphoramidates with formula C₆H₅C(O)N(H)P(O)R₂ (R = NC₃H₆ ( 1 ), NC₆H₁₂ ( 2 ), NHCH₂CH=CH₂ ( 3 ), N(C₃H₇)₂ ( 4 )) and CCl₃C(O)N(H)P(O)R′₂ (R′ = NC₃H₆ ( 5 ), NHCH₂CH=CH₂ ( 6 )) were synthesized and characterized by ¹H, ¹³C, ³¹P NMR and IR spectroscopy and elemental analysis. The structures were determined for compounds 1 and 2 . Compound 1 exists as two crystallographically independent molecules in crystal lattice. Both compounds 1 and 2 produced dimeric aggregates via intermolecular ‐P=O…H‐N‐ hydrogen bonds, which in compound 2 is a centrosymmetric dimer. In compounds with four‐membered ring amine groups, ³J(P,C)>²J(P,C), in agreement with our previous studies about five‐membered ring amine groups. Also, ³J(P,C) values in compounds 1 and 5 are greater than in compounds with five‐, six‐ and seven‐membered ring amine groups.     

A one-pot three-component approach to synthesis of novel dihydroxyoxoindeno[1,2-b]pyrrole derivatives

A new class of 2-arylamino-dihydroxyindenopyrroles were prepared by the one-pot multicomponent reaction of ninhydrin, N-methyl-1-(methylthio)-2-nitroethenamine and aromatic amines in EtOH at room temperature. The advantages of this procedure are short reaction times, good to high yields, easy separation of products and good functional group tolerance.     

Reversed‐phase vortex‐assisted liquid–liquid microextraction: A new sample preparation method for the determination of amygdalin in oil and kernel samples

A novel, simple, and rapid reversed‐phase vortex‐assisted liquid–liquid microextraction coupled with high‐performance liquid chromatography has been introduced for the extraction, clean‐up, and preconcentration of amygdalin in oil and kernel samples. In this technique, deionized water was used as the extracting solvent. Unlike the reversed‐phase dispersive liquid–liquid microextraction, dispersive solvent was eliminated in the proposed method. Various parameters that affected the extraction efficiency, such as extracting solvent volume and its pH, vortex, and centrifuging times were evaluated and optimized. The calibration curve shows good linearity (r² = 0.9955) and precision (RSD < 5.2%) in the range of 0.07–20 μg/mL. The limit of detection and limit of quantitation were 0.02 and 0.07 μg/mL, respectively. The recoveries were in the range of 96.0–102.0% with relative standard deviation values ranging from 4.0 to 5.1%. Unlike the conventional extraction methods for plant extracts, no evaporative and re‐solubilizing operations were needed in the proposed technique.     

A stepsize control algorithm for SDEs with small noise based on stochastic Runge–Kutta Maruyama methods

A variable stepsize control algorithm for solution of stochastic differential equations (SDEs) with a small noise parameter ?? is presented. In order to determine the optimal stepsize for each stage of the algorithm, an estimate of the global error is introduced based on the local error of the Stochastic Runge?CKutta Maruyama (SRKM) methods. Based on the relation of the stepsize and the small noise parameter, the local mean-square stochastic convergence order can be different from stage to stage. Using this relation, a strategy for producing and controlling the stepsize in the numerical integration of SDEs is proposed. Numerical experiments on several standard SDEs with small noise are presented to illustrate the effectiveness of this approach.     

Silica aerogel–iron oxide nanocomposites: recoverable catalysts for the oxidation of alcohols with hydrogen peroxide

Various aerogels of silica gel doped with Fe₂O₃ were prepared by sol–gel method. They were calcined to produce nanoparticle solids. The nanosized mixed oxides were active in the oxidation of alcohols and produced carbonyl compounds in very good to excellent yields using hydrogen peroxide.     

Efficient Synthesis of 2-Arylamino-2-imidazolines and 2-Ami-nobenzimidazoles with Aminoiminomethanesulfonic Acid Derivatives

A highly efficient synthesis of 2‐arylamino‐2‐imidazolines and 2‐aminobenzimidazoles from aminoimino‐methanesulfonic acid derivatives is described. The method is simple and practical, generating imidazoline and benzimidazoline derivatives in excellent isolated yields.     

Surfactant effect on the conductivity behavior of CsH2PO4: Characterization by electrochemical impedance spectroscopy

Cesium dihydrogen phosphate (CDP) nanoparticles were synthesized using the surfactants cetyltrimethyl ammonium bromide (CTAB), polyoxyethylene-polyoxypropylene (F-68) and (F-68:CTAB) with molar ratio 0.06. The samples conductivity such as CDP_CTAB, CDP_F-68 and CDP_{(F-68:CTAB)0.06} was studied by impedance spectroscopy in the frequency range 0.01 Hz to 1 MHz. The Nyquist plots were drawn at different temperatures of 210, 230 and 260 °C, which are defined below transition, phase transition and above transition, respectively. The measured conductivities obey the Arrhenius relation. The influence of surfactants on conductivity are more significant at higher temperature due to grain boundary. The conductivity of CDP_CTAB increased slightly with increasing temperature to 260 °C, whereas the conductivity of other samples decreased with increasing temperature over 230 °C. The results indicated that the conductivities increase in the order of CDP_CTAB>CDP_{(F-68:CTAB)0.06}>CDP_F-68. These are in accordance to the ion exchange capacities of the samples that the surfactant shows a direct influence on the samples proton mobility. It is found that the conductivity of CsH₂PO₄ is influenced by surfactant type.     

Olefin epoxidation with H2O2 in the presence of Mn(II) dicarboxylate coordination polymer catalysts

Abstract  

The Mn(II) dicarboxylate coordination polymers [Mn(μ-terephthalate)(H₂O)₂] _n , [Mn(μ-oxalate)(H₂O)₂] _n , and [Mn(μ-d-(−)-tartrate)] _n were prepared in water and characterized by FT-IR spectroscopy and CHN analysis. Particles of the terephthalate catalyst were also synthesized, by reaction of terephthalic acid and MnCl₂·4H₂O by a sonochemical method. The catalytic potential of these coordination polymers as slow-release sources of catalytically active Mn species was tested in the oxidation of cyclooctene to its epoxide in acetonitrile, using hydrogen peroxide as oxygen source. For the terephthalate species the catalytic activity was found to increase with increasing dielectric constant and dipole moment of the solvent (being highest in acetonitrile), with reaction temperature to a maximum at 60 °C, and with an imidazole co-catalyst (highest activity found for a imidazole-to-catalyst molar ratio of 20:1). Good activity with more than 64% conversion in 24 h was obtained for epoxidation of cyclooctene and cyclohexene, whereas low yields only were obtained from aryl-substituted olefins. Some exo versus endo regioselectivity was found for norbornene.     

Semi-empirical and ab initio quantum chemical characterisation of pyridine derivatives as HCl inhibitors of aluminium surface

Quantum chemical methods are becoming ever more prevalent for assessing surface interactions of different molecules using cluster models and semi-empirical, ab initio Hartree–Fock and density functional theory (DFT) studies considering the standard potential energy surfaces. Examination of the efficacy of some pyridine derivatives to counter aluminium corrosion in hydrochloric acid using ab initio and semi-empirical quantum chemical deductions and its comparison with the available experimental data forms the basis of this research. It is believed that the inhibition efficiency has lucid correlation with the total energy of inhibitor molecules and highest occupied molecular orbital energy levels calculated by DFT study methods and thus the adsorption energy for the pyridine on Al₁, Al₅, Al₁₄, Al₁₈ and Al₂₆ clusters are determined to assess the convergence of the results with respect to size of the cluster. Subsequently, Al₂₆ is used for the inhibitor/aluminium cluster interface investigations. Results highlight the reaction between pyridine molecules and appropriately active sites such as corners and steps or kinks and screw dislocations towards which pyridine molecules are attracted as is evident from a three times rise in adsorption energy from (−35) to (−107) kJ mol⁻¹. Therefore, inhibition mechanism is primarily associated with local properties. Interactions take place between the surface defect and the nitrogen group of the pyridine molecule however, the possibility of ion pair formation between protonated pyridine and chloride ion and its influence on the general adsorption of pyridine on aluminium is also examined. The interaction energies of pyridine and aluminium cluster with the natural bond orbital are also reported.