Silica Chromate as a Novel Oxidizing Agent for the Oxidation of 1,4‐Dihydropyridines

Silica chromate easily converts 1,4‐dihydropyridines to their corresponding pyridines in the presence of NaHSO₄ · H₂O and wet SiO₂ in dichloromethane at room temperature in good to excellent yields.     

Enantioselective Diethylzinc Addition to Aromatic Aldehydes Catalyzed by Novel Ti(IV) Complex of Three-Dentate Chiral Sulfonamide Ligands

The synthesis of several novel three-dentate sulfonamide alcohol ligands is described, starting from camphorsulfonyl chloride. The influence of temperature and ligand structure on the asymmetric addition of dietylzinc to aromatic aldehydes has been studied. Enantioselectivities up to 76% have been obtained.     

Multi-objective optimization on the machining parameters for bio-inspired nanocoolant

Journal of Thermal Analysis and Calorimetry - The emphasis of this paper is to evaluate the thermophysical properties of crystalline nanocellulose (CNC)-based nanofluid and the optimized machining...     

A green and selective synthesis of 2‐aryloxazines and 2‐aryltetrahydropyrimidines

An efficient method for the selective synthesis of 2‐substituted oxazines and tetrahydropyrimidines by the reaction of arylnitriles with 3‐amino‐1‐propanol and 1,3‐diaminopropane in the presence of montmorillonite K‐10 and KSF as inexpensive, environmentally benign, and reusable catalysts under classical heating conditions and microwave irradiation is reported. J. Heterocyclic Chem., (2011).     

ALANINE/CHLOROCHROMIC ACID/SILICA GEL: AN EFFICIENT AND SELECTIVE REAGENT FOR THE OXIDATION OF ORGANIC FUNCTIONAL GROUPS

Alanine/chlorochromic acid/silica gel is a new and selective reagent for the efficient oxidation of sulfides, thiols, oximes, and alcohols. Oxidation of sulfides is solvent dependent. In chloroform at room temperature sulfoxides are formed as the major products, while in carbon tetrachloride or under solvent-free conditions solfones are produced in good-to-excellent yields.     

Acidified,Wet, Silica-Supported Tetrabutylammonium Periodate: A Convenient and Mild Reagent for Conversion of Thioamides to Their Corresponding Amides Under Solvent-Free Conditions

A series of thioamides are transformed to their corresponding oxo analogues in good to excellent yields with acidified, wet, silica-supported tetrabutylammonium periodate under solvent-free conditions.     

Infrared chemical imaging: Spatial resolution evaluation and super-resolution concept

Chemical imaging systems help to solve many challenges in various scientific fields. Able to deliver rapid spatial and chemical information, modern infrared spectrometers using Focal Plane Array detectors (FPA) are of great interest. Considering conventional infrared spectrometers with a single element detector, we can consider that the diffraction-limited spatial resolution is more or less equal to the wavelength of the light (i.e. 2.5-25 μm). Unfortunately, the spatial resolution of FPA spectroscopic setup is even lower due to the detector pixel size. This becomes a real constraint when micron-sized samples are analysed. New chemometrics methods are thus of great interest to overcome such resolution drawback, while keeping our far-field infrared imaging spectrometers. The aim of the present work is to evaluate the super-resolution concept in order to increase the spatial resolution of infrared imaging spectrometers using FPA detectors. The main idea of super-resolution is the fusion of several low-resolution images of the same sample to obtain a higher-resolution image. Applying the super-resolution concept on a relatively low number of FPA acquisitions, it was possible to observe a 30% decrease in spatial resolution.     

A comparative MP2 study between water- and acid-assisted proton transfer: allophanic acid as a case of study

Electronic structures of allophanic acid were studied using MP2/6-311++G(d,p) level of theory. Five most stable tautomers were selected and stability of them was studied in detail. Obtained data showed that tautomer 1 having hydrogen atom in the central nitrogen N3 and also in a trans conformation of carbonyl and amino functional groups becomes the most stable one. Then, interconversion of these tautomers to each other was investigated step by step through internal rotation and proton transfer routes. Results indicated that movement of protons determines rate-determining step of all paths A–E. Effects of different solvents were carefully surveyed for each tautomer, and among investigated solvents, water made slight stabilization. Activation barrier for proton exchange assisted by one water molecule and one formic acid molecule was also studied, separately. Both molecules had a great influence on lowering barrier especially for proton transfer routes. Comparative MP2 study showed that the barrier will be lowered much more when acid-assisted proton exchange takes place.     

Structure and photoluminescence properties of TiO<Subscript>2</Subscript> nanoparticles synthesized from a novel luminescent nano-titanium complex

A new titanium complex [Ti(Me–Q)₂(Cl)₂] (1) is prepared by reacting titanium tetrachloride with 2-methyl-8-hydroxyquinoline in a fast and facile process. The complex is fully characterized based on its ¹H and ¹³C NMR, IR, and UV spectra and elemental analysis. The prepared nanostructured compound is synthesized by the sonochemical method. This new nanostructure is characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), IR spectroscopy, and elemental analysis. Thermal stability of single crystalline and nanosize samples of the prepared compound is studied by thermal gravimetric (TG) and differential thermal analysis (DTA). The prepared complexes both bulk and nanosized are utilized as a precursor for the preparation of TiO₂ nanoparticles by direct thermal decomposition at 600°C in air. The morphology and size of TiO₂ nanoparticles are determined by SEM, powder XRD, and IR spectroscopy and the results show that the TiO₂ nanoparticle size depends on the initial particle size of 1. Photoluminescence (PL) properties of the nanostructured and crystalline bulk prepared complex and their TiO₂ nanoparticle cores are investigated.     

Ionic strength dependence of stability constants,complexation of W(VI) with iminodiacetic acid

The equilibria between tungsten(VI) and iminodiacetic acid (IDA) have been studied in aqueous solution. The stoichiometry and stability constants of the complexes formed are determined from a combination of potentiometric and Uv spectroscopic measurements. All measurements are carried out at 25°C, pH 7.5 and different ionic strengths ranging from (0.1 to 1.0) mol dm⁻³ (NaClO₄). According to these results, tungsten(VI) forms a mononuclear complex with IDA of the type (WO₃L²⁻). By introducing two empirical parameters C and D in the complex-formation reaction between tungsten(VI) and IDA, the dependence of the dissociation and stability constants on ionic strength is described by a modified Debye-Huckel-type equation. Finally, a pattern for the ionic strength dependence is obtained.