Ag nanoparticles for determination of bisphenol A by resonance light-scattering technique

Resonance light-scattering (RLS) technique was developed for studying the interaction of silver nanoparticles (Ag NPs) with bisphenol A. A simple and environmentally friendly method was developed to synthesize Ag NPs using cinnamon extract. Synthesized nanoparticles were characterized using various measurement techniques. The synthesized Ag NPs were nearly spherical, with the sizes ranging from 30 to 60 nm. Spectral analysis indicated that the cinnamon extract acted as the reducing and capping agents on the surface of Ag NPs. RLS technique was used as the detection method. Light-scattering properties of the synthesized nanoparticles in the presence or absence of bisphenol A was selected as the detection signal. Under the optimal conditions, the linear dynamic range and RSD were found to be 0.01–10.0 mg L^?1 and 2.78% (n?=?3), respectively. A limit of detection of 0.005 mg L^?1 was obtained for the determination of bisphenol A. The obtained results showed successful application of the method for the analysis of bisphenol A in real samples.     

Conductance study of complex formation of thallium and silver ions with several crown ethers in acetonitrile,acetone and dimethylformamide solutions

The complexation reactions between Tl⁺ and Ag⁺ ions and several crown ethers have been studied conductometrically in acetonitrile, acetone and dimethylformamide solutions at 25°C. The stability constants of the resulting 1:1 complexes were determined, and found to decrease in the order DA18C6>DC18C6>DB30C10>18C6>DB21C7>DB24C8>DB18C6>B15C5 >12C4, in the case of Tl⁺ complexes, and in the order DA18C6>DC18C6>18C6>DB18C6 >DB24C8>DB30C10B15C5>DB21C7 for Ag⁺ complexes. There is an inverse relationship between the stabilities of the complexes and the Gutamnn donicity of the solvents. The influence of a number of atoms in the macrocycle and of substituents in the polyether ring on the stability of the complexes is discussed.     

Green Oxidations. Manganese(II) Sulfate Aided Oxidations of Organic Compounds by Potassium Permanganate

Summary. The oxidation of arenes and sulfides by potassium permanganate was accomplished in good yields under solvent free and heterogeneous conditions when manganese(II) sulfate is used as a solid support. After extraction of the organic products, the inorganic products can be reoxidized to permanganate. This result is important because it provides an approach to oxidation reactions that is, in theory, infinitely sustainable.     

Synthesis of Substituted Pyrazino[5,6-b]pyrimidine and Some Indole Derivatives

Refluxing dimethyl acetylenedicarboxylate (DMAD) or 1,2-dibenzoylacetylene with isatin-3-thiosemicarbazone or isatin-3-thiocarbohydrazone in methanol produced 3-substituted oxindoles in good yields. Reaction of equimolecular amounts of 5,6-diamino-urasil-solfate, trans-(1R,2R)-diaminocyclohexane, and 3,4-diamino-1,2,4-triazol-5-methyl hydrochlorid with isatin in ethanol (85%) afforded tetracyclic ring systems and ring-opened products in mild reaction conditions.     

CuI‐functionalized halloysite nanoclay as an efficient heterogeneous catalyst for promoting click reactions: Combination of experimental and computational chemistry

Amine‐functionalized halloysite nanotubes (HNTs‐2 N) were prepared and further modified by introduction of salicylaldehyde and formation of imine functionality (HNTs‐2 N‐Sal). The latter was subsequently used for immobilization of CuI and formation of CuI@HNTs‐2 N‐Sal, which could effectively promote click reactions of terminal alkynes, sodium azide and α‐haloketones or alkyl halides in aqueous media and under mild reaction conditions to afford 1,2,3‐triazoles in relatively short reaction times. Notably, the catalyst could be recycled in up to six reaction runs with negligible loss of catalytic activity and CuI leaching. Also, the geometry of CuI adsorption on the modified HNTs surface was explored by molecular simulation with density functional theory. Furthermore, topographic steric maps of possible coordination modes were obtained using the recently released SambVca2 web application tool. Based on obtained results, a catalytic site with superior performance was suggested.     

Ultrasonic and bio‐assisted synthesis of Ag@HNTs‐T as a novel heterogeneous catalyst for the green synthesis of propargylamines: A combination of experimental and computational study

A novel heterogeneous catalyst is prepared through functionalization of halloysite nanotube with 1H‐1,2,3‐triazole‐5‐methanol and subsequent immobilization of silver nanoparticles through bio‐assisted approach using Arctiumplatylepis extract. The resulting catalyst, Ag@HNTs‐T, was characterized by using SEM/EDX, BET, XRD, FTIR, ICP‐AES, TGA, DTGA and elemental mapping analysis. Moreover, we computationally assessed metal‐ligand interactions in Ag@HNTs‐T complex model to interpret the immobilization behavior of silver nanoparticles on HNTs surface via quantum chemistry computations. The catalytic activity of the catalyst was studied for the synthesis of propargylamines via A³ and KA² coupling reactions under ultrasonic irradiation. The results demonstrated that Ag@HNTs‐T could efficiently promote these reactions to furnish the corresponding products in high yields and short reaction times. The study of the recyclability of the catalyst and Ag(0) leaching confirmed that the catalyst was recyclability up to four reaction runs with slight Ag(0) leaching.     

Synthesis and characterization of sodium polyaspartate‐functionalized silica‐coated magnetite nanoparticles: A heterogeneous,reusable and magnetically separable catalyst for the solvent‐free synthesis of 2‐amino‐4H‐chromene derivatives

An efficient and facile method was used for the synthesis of sodium polyaspartate‐functionalized silica‐coated magnetite nanoparticles. The structure of this nanoparticle was characterized by scanning electron microscopies, X‐ray diffraction, energy‐dispersive X‐ray, Fourier transform infrared spectroscopies and vibrating sample magnetometry. Then, this compound was used as a reusable heterogeneous catalyst for green synthesis of 2‐amino‐4H‐chromene derivatives via one‐pot three‐component reactions. This novel material showed great catalytic performance and the reactions which were carried out by this catalyst showed good to excellent yields. Besides, the catalyst could easily be separated from the reaction mixture by using an external magnetic field and it was stable enough to reuse several times without any significant reduction in the yield of reactions. Eco‐friendliness, high purity of the desired products, short reaction time and easy workup procedure can be mentioned as the other advantages of this method.     

Palladium-catalyzed domino protodecarboxylation/oxidative Heck reaction: regioselective arylation of coumarin-3-carboxylic acids

A protocol for straightforward and step-economical synthesis of neoflavones from coumarin-3-carboxylic acids is developed. This approach enables controlled protodecarboxylation/regioselective C–H arylation of coumain-3-carboxylic acids in one-pot using a monometallic catalytic system. A wide variety of electron-donating and -withdrawing substituents on both coumarins and arylboronic acid are tolerated under the reaction conditions and 4-aryl coumarins are constructed in high yields.     

KBrO3/MoO3： An efficient reagent system for the oxidative deprotection of semicarbazones, 1,1-diacetates and acetals

Semicarbazones,1,1-diacetates and acetals are efficiently converted to their corresponding carbonyl compounds using synergistic effect between KBrO3 and MoO3 in refluxing CH3CN-H20 in good to high yields.