Straightforward Approach Toward Dihydrothiazoles via Intramolecular Bromocyclization

An intramolecular bromonium ion–assisted cyclization with sulfur as an internal nucleophile is described. Starting from benzoyl chlorides, this method provides an easy procedure for the synthesis of dihydrothiazole derivatives in moderate to good yields.     

First immobilization of a glycoluril-derived molecular clip on Merrifield resin: facile separation of dihydroxybenzenes by affinity chromatography

A practical method for the separation and purification of dihydroxybenzenes from phenol-dihydroxybenzene, methoxyphenol-dihydroxybenzene, and isomeric dihydroxybenzene mixtures was developed on the basis of affinity chromatography using a functionalized Merrifield resin. The resin was obtained by immobilization of a glycoluril-derived clip on Merrifield resin. This recyclable resin was repeatedly used for convenient and rapid separation of dihydroxybenzenes from the above-mentioned mixtures.     

Chemistry of biureas—II: Synthesis and cyclisation of thiobiureas derived from (thio)carbonohydrazides and ethoxycarbonyl isothiocyanate

Carbonohydrazide and its thio-analogue undergo di-addition with ethoxycarbonyl isothiocyanate. The reaction terminates at the mono-addition stage when one of the hydrazine moieties of the (thio)carbonohydrazide is blocked. The resulting 6-(substiiuted)amino-1-ethoxycarbonyl-thiobiureas and bithioureas are cyclised to the appropriate 1-ethoxycarbonamido-1,3,4-thiadiazoles by acids, and to mercapto-1,2,4-triazoles by alkalis.     

The Effect of Blending Sequence on Nanoclay Partitioning and Microfibrillar Morphology in Blend Nanocomposite Fibers

The aim of this article was to provide an insight into the effect of nanoclay partitioning on the droplet deformation and fibril formation in melt-compounded polypropylene/poly (butylene terephthalate)/organoclay blend nanocomposite fibers prepared by different blending sequences. An attempt was also made to investigate the effect of compatibilizer on the partitioning of nanoclay in these blend systems. Melt viscoelastic behavior, wide angle X-ray diffraction and transmission electron microscopy, along with scanning electron microscopy, revealed that the localization of nanoclay in the poly (butylene terephthalate) dispersed phase reduced the droplet deformation and fibril formation. It was demonstrated that the best microstructure of the blend nanocomposites for the fibrillation process was to have the maximum percentage of exfoliated nanoclay in both polymeric phases. Incorporation of compatibilizer can develop the microfibrillar morphology due to its assisting role in transferring a higher fraction of nanoclay platelets from droplets into the matrix and also increasing the extent of melt intercalation in the matrix.     

Synthesis and anticancer activity of new azo compounds containing extended π-conjugated systems

A series of novel azo compounds with extended π-conjugated systems were prepared by azo coupling reaction compounds trans-2-(4′-aminostyryl)-thiophene, 1-(4-aminophenyl)-4-phenyl-1,3-butadiene and 4-amino-4′-methoxystilbene with some phenols. The compounds were evaluated for their cytotoxicity against breast cancer adenocarcinoma (MCF-7), cervix adenocarcinoma (HeLa) and human embryonic kidney (HEK 293) cell lines using the MTT assay. The results showed all derivatives had more toxic effects than tamoxifen. Of all the compounds tested, the azo product obtained from coupling trans-2-(4′-Aminostyryl)-thiophene with 2-naphthol (compound 5b) exhibited the potent in vitro antiproliferative activity with IC₅₀ 27 ± 1 and 18 ± 0 µg/mL against MCF-7 and HeLa cell lines, respectively, while it was devoid of any cytotoxicity against normal HEK 293 cells even at 200 µg/mL.     

The Effect of Magnesium Chloride Hydrate on the Fire Retardation of Cellulosic Fibers

Thermal analysis was used to investigate the effect of the addition of magnesium chloride hexahydrate as a fire retardant to cellulosic fibers. The kinetics of the decomposition of the cellulosic material were first studied. The decomposition of the dry salt was also investigated and three steps disclosed. Then, the fabrics were impregnated into salt solutions of different concentrations and the loss in mass was followed by thermal analysis. The percent loss in mass was compared to that of pure cellulosic fabric at different temperatures. It was found that there is an appreciable improvement in fire retardation at a minimum percent add-on of the salt of 35%. This revised version was published online in August 2006 with corrections to the Cover Date.     

An ab initio study on substituent and cooperative effects in bifurcated fluorine bonds

Bifurcated fluorine bond (BFB) interactions are studied in model binary complexes pairing N-formyl formamide derivatives and FX molecules (X = F, CN, NC, CF₃ and CCH) by means of ab initio calculations. The calculated F···O binding distances in these complexes are in the range of 2.813–3.048 Å. The corresponding interaction energies lie in a narrow range, from?2.25 to ?16.49 kJ/mol. The nature of BFBs is analysed by a vast number of methods including molecular electrostatic potential, quantum theory of atoms in molecules, non-covalent interaction index and natural bond orbital methods. According to the energy decomposition analysis, the electrostatic and dispersion effects have a dominant role in the formation of these complexes. The formation of a hydrogen- and lithium-bonding interaction tends to increase the strength of BFBs in the ternary XF:NFF-H:NH₃ and XF:NFF-Li:NH₃ complexes, respectively.     

The effect of electric field and Al doping on the sensitivity of hexa‐peri‐hexabenzocoronene nanographene to chloropicrin

It has been previously reported that the recently synthesized hexa‐peri‐hexabenzocoronene (HBC) nanographene cannot detect toxic chloropicrin (CP) gas. To overcome this problem, we examined the effect of Al doping and applying an electric field on the sensitivity of HBC towards CP gas by means of density functional theory calculations. We found that the Al‐doping process significantly increases the adsorption energy of CP gas from ?7.1 to ?39.9 kcal mol^?1 but decreases the sensitivity of HBC. By applying an electric field, the HBC is polarized with two different electrostatic potentials on its different surfaces, which increases the adsorption energy. By increasing the electric field strength, the adsorption energy and electronic sensitivity of HBC are increased. We predicted that in the presence of an electric field of about ?0.025 au, HBC can act as an electronic senor or a work function‐type sensor with a short recovery time. At this field, the electrical conductivity of HBC is significantly increased on CP adsorption which generates an electrical signal. Increasing the electric field to higher intensities is not favourable because of increasing recovery times, and decreasing it to lower intensities reduces the sensitivity of HBC.     

Weak flocculation of aqueous kaolin suspensions initiating by NaCMC with different molecular weights

The present work is an investigation of the effect of NaCMC with different viscosities (molecular weights) on the stability of aqueous kaolin suspensions at pH 5-6. The stabilizing effect of polymers was characterized by measuring the sedimentation volumes (for 2.5% kaolin suspensions) and some important rheological parameters (for 40% and 50% kaolin suspensions). In certain cases the stability of suspensions was also studied in the presence of 0.5-1.0% NaCl. The additives were incorporated into the suspensions separately and simultaneously, as well. In certain cases the effect of mixing order of NaCMCs was also studied. The lower viscosity NaCMC was found to be a better stabilizing agent than its medium viscosity counterpart at the studied polymer concentrations (0.005-1.0%). This was manifested in smaller sedimentation volumes and lower rheological parameters (viscosity, yield stress, degree of thixotropy and elasticity). The lower and the medium viscosity polymer were simultaneously and consecutively added in a mass ratio of 50:1 and 10:1. The resulted observation of low viscosity and yield stress, and more importantly thixotropy and elasticity, can be interpreted in terms of a “site-blocking” type flocculation.