The Synthesis of 1,4-Diaza-2,3;8,9-dibenzo-7,10-dioxacyclododecane-5,12-dione and Its Use in Calcium-Selective Carbon Paste Electrodes

A synthetic procedure has been developed for the preparation of1,4-diaza-2,3;8,9-dibenzo-7,10-dioxacyclododecane-5,12-dione. A carbon paste electrode based on the new macrocyclic diamide was constructed for Ca²⁺determination. The calibration graph was linear over a wide concentration range (1.3 × 10^-6–3.2 × 10^-3 M) with a near Nernstianslope of 32 mV decade^-1. The limit of detection is 7.9 × 10^-7 M (0.032 ppm).Selectivity coefficients were tabulated and the working pH range was determined. It has a fast response time of <10 s and can be used for at least 3 months without any considerable divergence in potentials. The electrode was successfully applied to the determination of Ca²⁺ ions in a pharmaceutical preparation.     

Cesium-selective membrane electrode based on a recently synthesized 16-membered macrocyclic diamide

A PVC membrane sensor for the Cs+ ion based on 1,5-diaza-2,3,4-naphthyl-8,11,14-trioxacyclohexadecane-6,16-dione (L) has been prepared. The sensor has a linear dynamic range of 5.0 x 10(-1) - 6.9 x 10(-6) mol L(-1), a Nernstian slope of 59.5 +/- 0.8 mV decade(-1), and a detection limit of 4.7 x 10(-6) mol L(-1). It has a fast response time of <15 s and can be used for at least 8 weeks without any considerable divergence in potentials. The selectivity of the proposed electrode relative to alkali, alkaline earth, and transition metal ions was comparatively good. The electrode could be used in the pH range 4.5-11.0.     

三溴异氰脲酸和DABCI-Br作为高效催化剂用于羟基硅烷化

The protection and deprotection of functionalgroups are indispensable in the synthesis of polyfunc-tional compounds.In addition,several chemical con-versions and multiple sequence syntheses are often re-quired for the protection of hydroxyl groups.Thesily…     

PEG‐N2O4 System as an Efficient Reagent both for the Rapid Oxidation of Urazoles and 1,4‐Dihydropyridines under Nonaqueous Conditions

N₂O₄ was easily impregnated on polyethyleneglycol to give a stable reagent. Polyethyleneglycol‐N₂O₄ ( PEG‐N₂O₄ ) system was used as an effective oxidizing agent for the oxidation of urazoles and bis‐urazoles to their corresponding triazolinediones and also for the aromatization of 1,4‐dihydropyridines into the corresponding pyridine derivatives under mild conditions at room temperature with good to excellent yields.     

Effects of relativistic and ponderomotive nonlinearities on the interaction of high-power laser beam with an inhomogeneous warm plasma

The influence of relativistic-ponderomotive nonlinearities and the plasma inhomogeneity on the nonlinear interaction between a high-power laser beam and a warm underdense plasma are studied. It is clear that the relativistic ponderomotive force and the electron temperature modify the electron density distribution and consequently change the dielectric permittivity of the plasma. Therefore, by presenting the modified electron density and the nonlinear dielectric permittivity of the warm plasma, the electromagnetic wave equation for the propagation of intense laser beam through the plasma is derived. This nonlinear equation is numerically solved and the distributions of electromagnetic fields in the plasma, the variations of electron density, and plasma refractive index are investigated for two different background electron density profiles. The results show that the amplitude of the electric field and electron density oscillations gradually increase and decrease, during propagation in the inhomogeneous warm plasma with linear and exponential density profiles, respectively, and the distribution of electron density becomes extremely sharp in the presence of intense laser beam. It is also indicated that the electron temperature and initial electron density have an impact on the propagation of the laser beam in the plasma and change the plasma refractive index and the oscillations' amplitude and frequency. The obtained results indicate the importance of a proper choice of laser and plasma parameters on the electromagnetic field distributions, density steepening, and plasma refractive index variations in the interaction of an intense laser beam with an inhomogeneous warm plasma.     

Silica-bonded S-Sulfonic Acid: A Recyclable Catalyst for the Synthesis of Trisubstituted Imidazoles under Solvent-free Conditions

Trisubstituted imidazoles have been synthesized in high yields in the presence of silica‐bonded S‐sulfonic acid as a catalyst. The reaction was carried out at 130°C under solvent‐free conditions. The reaction work‐up is simple and the catalyst is easily separated from the products by filtration.     

Molybdatophosphoric Acid/NaNO2 as an Efficient Procedure for the Chemoselective N‐Nitrosation of Secondary Amines

A combination of molybdatophosphoric acid and sodium nitrite in the presence of wet SiO₂ was used as an effective nitrosating agent for the nitrosation of secondary amines under mild and heterogeneous conditions in good to excellent yields. Also, the results of a computational study are investigated in the gas phase for geometry and properties of proposed structures.