MICROWAVE ASSISTED OXIDATION OF BENZALDEHYDES UNDER SOLVENT-FREE CONDITION USING OXONE®/WET-ALUMINA

The solventless oxidation of benzaldehydes to carboxylic acids using oxone/wet-alumina under microwave irradiations is described.     

Preparation of magnetic polyurethane rigid foam nanocomposites

Super paramagnetic Fe₃O₄@SiO₂ nanoparticle was incorporated into polyurethane rigid foams in order to prepare new corresponded magnetic nanocomposite foams via one-shot method. The core–shell-structured nanoparticles were prepared by sol–gel method and characterized by transmission electron microscopy, X-ray diffraction, as well as Fourier transform infrared spectroscopy techniques. Magnetic nanoparticles were used up to 3 % in the foam formulations and the samples prepared successfully. Thermal, mechanical, and magnetic properties of nanocomposites were studied and the results showed superior properties in comparison with pristine foams.     

Thermally Stable Magnetic Polyurethane Nanocomposites Prepared from Functionalized Polybutadiene: Novel Approach to the Polybutadiene Chemical Modification

Russian Journal of Applied Chemistry - In this work, preparation and characterization of new classes of polybutadiene-based polyols and polyurethanes investigated with consecutive reactions namely,...     

Synthesis,Characterization and Physicomechanical Properties of Novel Water-based Biodegradable Polyurethane Dispersion

Novel water-based biodegradable polyurethane dispersions with an aim to develop environmentally friendly materials, including medicine, various industries, have been prepared in this study. Biodegradable ionic polyurethanes (IPU) were synthesized based on polyols from renewable resources, such as castor oil (CO), in the presence of a polyester polyol and polyethylene glycol (PEG) with hydrophilic property and 1,6-hexamethylene diisocyanate. 1,4-Butanediol and dibutyltin dilaurate, were used as a chain extender and catalyst, respectively. The comprehensive investigations of the structure and properties of five types of synthesized polyurethanes demonstrated biodegradability relationship of these polyurethanes with their structure and composition. In this research effects of different types and content of polyols on biodegradability and physico mechanical properties of prepared PUDs were investigated. The structure, properties and physico mechanical and application behavior of mentioned materials were characterized by ¹H NMR, FTIR spectroscopy, thermogravimetric analysis (TG/DTG) and dynamic mechanical thermal analysis (DMTA). The adhesion properties were measured by pull off test as well. Particle size was measured by dynamic light scattering (DLS) methods. The biodegradability of prepared polyurethane dispersions was confirmed by water uptake, hydrolytic and enzymatic degradation in phosphate buffer saline (PBS) with lipase enzyme in PBS. Results showed that by the incorporation of natural components into the polymer chain, adjusting of hydrophilic and hydrolytic liability properties of soft segments and especial relevant designs, useful polyurethane can be synthesized with desirable property of biodegradability and dispersion stability. Except for one sample, other samples were decomposed totally in enzymatic media.     

An Efficient and Rapid Chemoselective Synthesis of α-Aryl-N-methylnitrones Dry Media

 A simple, efficient, and eco-friendly procedure was developed for the condensation of N-methylhydroxylamine hydrochloride with benzaldehydes bearing electron-donating or electron-withdrawing substituents in the presence of powdered molecular sieves (3 ?) in a solventless system. α-Aryl-N-methylnitrones are obtained in excellent yields (80–100%); similar aromatic ketones do not react under these conditions, rendering the method chemoselective.     

An Efficient and Rapid Chemoselective Synthesis of α-Aryl-N-methylnitrones Dry Media

Summary.  A simple, efficient, and eco-friendly procedure was developed for the condensation of N-methylhydroxylamine hydrochloride with benzaldehydes bearing electron-donating or electron-withdrawing substituents in the presence of powdered molecular sieves (3 ?) in a solventless system. α-Aryl-N-methylnitrones are obtained in excellent yields (80–100%); similar aromatic ketones do not react under these conditions, rendering the method chemoselective. Received March 26, 2001. Accepted (revised) May 7, 2001     

A FACILE AND NEW METHOD FOR THE SYNTHESIS OF α-ARYL-N-METHYLNITRONES IN SOLVENT-FREE MEDIA USING SILICA GEL-NaOH

Substituted α-aryl-N-methylnitrones are prepared by the condensation reaction of N-methylhydroxylamine hydrochloride and benzaldehydes in solvent-free media using silica-gel–NaOH catalyst system. The yields are excellent regardless of the electron-donating or electron-accepting nature of the substituents on benzaldehyde. Similar ketones are unreactive under these conditions, rendering chemoselectivity of the method.     

Properties of Modified Hexagonal Boron Nitride as Stable Nanofluids for Thermal Management Applications

Russian Journal of Applied Chemistry - In this report, hexadecylamine (HDA) as a Lewis base was used to prepare exfoliated layers of modified hexagonal boron nitride h-BN (mh-BN) via two distinct...     

Magnetic Fe3O4/SiO2/NH2 As the Recyclable Heterogeneous Nanocatalyst on Bisphenol-A Recovery from Polycarbonate Wastes

Polycarbonate (PC) wastes received from optical (CDs) and digital optical discs (DVDs) were chemical recycled by using diethylene glycol (DEG) and water as an alternative green solvents and magnetite nanomaterials coated with amine modified silica nanoshell (Fe₃O₄/SiO₂/NH₂) as the recyclable heterogeneous catalyst to recover bisphenol-A (BPA) as a valuable material in 100% yield and without using harmful reagent and environmental problems. The nano-magnetic heterogeneous catalyst can be recycled for four cycles and used next reaction. The recovered BPA and nanomaterials were examined with transmission electron microscopy (TEM), thermogravimetric analysis (TGA), X-ray powder diffraction (XRD), and spectroscopic methods (¹H NMR, ¹³C NMR, FTIR).