Introduction of a novel dicationic Brönsted acidic ionic liquid based on pyrazine and its application in the synthesis of xanthenediones and 3, 4-dihydropyrimidin-2(1H)-ones under solvent-free conditions

Research on Chemical Intermediates - A novel dicationic Brönsted acidic ionic liquid based on pyrazine has been prepared and characterized by FTIR, 1H NMR, 13C NMR, MS, thermal gravimetric and...     

Kinetic–Spectrophotometric Determination of Trace Silver(I) Using Its Catalytic Effect on the Oxidation Reaction of Fuchsin by Peroxodisulfate in the Presence of 1,10-Phenanthroline As an Activator

A kinetic spectrophotometric method for the determination of trace amounts of Ag(I) in the range of 2–20 ng mL^–1 is reported. The method is based on the catalytic effect of Ag(I) on the oxidation reaction of fuschin by potassium peroxodisulfate in the presence of 1,10-phenanthroline as an activator at pH = 5. The reaction is followed spectrophotometrically by measuring the change in absorbance (A) at 544 nm using a fixed time method (6 min). The reaction variables were optimized in order to achieve the highest sensitivity. The 3s criterion detection limit was 0.7 ng mL^–1, and the relative standard deviation for ten replicate measurements of 16 ng mL^–1 of Ag(I) was 0.95% (n = 10). The method was successfully applied to the determination of silver in expired black and white photographic films and results showed good agreements with those obtained by atomic absorption spectrometry.     

Aromatization of <Emphasis Type="Italic">Hantzsch</Emphasis> 1,4-Dihydropyridines by Hydrogen Peroxide in the Presence of Cobalt(II) Acetate

Summary.  Hydrogen peroxide readily oxidizes Hantzsch type 1,4-dihydropyridines in the presence of cobalt(II) acetate as catalyst at room temperature. No evidence of a dealkylation process for 4-alkyl 1,4-dihydropyridines has been observed. Corresponding author. E-mail: mhashemi@sharif.ac.ir Received January 16, 2002; accepted (revised) April 20, 2002     

Room Temperature Catalytic Aromatization of Hantzsch 1,4-Dihydropyridines by Sodium Nitrite in the Presence of Acidic Silica Gel

Summary. Various alkyl, aryl, and heterocyclic Hantzsch 1,4-dihydropyridines were converted to the corresponding pyridines in excellent yields and short times using sodium nitrite in the presence of a catalytic amount of acidic silica gel at room temperature.     

Hydrodistillation–Solvent Microextraction and GC–MS Identification of Volatile Components of Artemisia aucheri

A new, simple hydrodistillation–solvent microextraction (HD–SME) technique has been used for analysis of the volatile components of the aerial parts of Artemisia aucheri. The components were collected in a single microdrop, and this was injected directly for gas chromatographic–mass spectrometric (GC–MS) analysis. The effects on extraction efficiency of extraction solvent, sample mass, microdrop volume, and extraction time were optimized by use of a simplex method. The identities of the components of HD–SME extracts were confirmed according to their retention indexes and mass spectra with those of standards. Forty components were extracted and identified by use of the method; 1,8-cineol (22.8%), chrysanthenone (18.16%), α-pinene (8.33%), and mesitylene (7.41%) were the major constituents. The results obtained from the microextraction method were compared with those obtained by conventional hydrodistillation.     

A green and efficient deoximation using H_2O_2 catalyzed by montmorillonite-K10 supported CoCl_2

Oximes were oxidized to the corresponding carbonyl compounds in good to high yields by environmentally friendly and green oxidant,H_2O_2 catalyzed by montmorillonite K-10 supported cobalt(Ⅱ) chloride.     

Uniform silver nanoparticles on tunable porous N‐doped carbon nanospheres for aerobic oxidative synthesis of aryl nitriles from benzylic alcohols

Tunable N‐doped carbon nanospheres from sucrose as carbon source and Tris(2‐aminoethyl)amine (TAEA) as nitrogen source by a simple and easily reproducible method were prepared. It was demonstrated that the tunable N‐doping of carbon spheres could be realized by altering the ratio of TAEA in the raw materials. The content of doped nitrogen, surface area, pore volume and pore size of carbon nanospheres were increased with the increasing of TAEA amount in the hydrothermal process. Prepared N‐doped carbon nanospheres act as solid ligand for anchoring of Ag NPs which generated via chemical reduction of Ag ions. Benzylic alcohols and aldehydes were converted into the aryl nitriles by using Ag/N‐CS‐1 nanospheres as the catalyst and O₂ as the oxidant, efficiently. This catalyst was stable and could use for 6 successful runs.