Preparation of Silica‐bonded Propyl‐diethylene‐triamine‐N‐sulfamic Acid as a Recyclable Catalyst for Chemoselective Synthesis of 1,1‐Diacetates

A simple and efficient procedure for the preparation of silica‐bonded propyl‐diethylene‐triamine‐N‐sulfamic acid (SPDTSA) by reaction of 3‐diethylenetriamine‐propylsilica (DTPS) and chlorosulfonic acid in chloroform is described. Silica‐bonded propyl‐diethylene‐triamine‐N‐sulfamic acid is employed as a recyclable catalyst for the synthesis of 1,1‐diacetates from aromatic aldehydes and acetic anhydride under mild and solvent‐free conditions at room temperature. Catalyst could be recycled for several times without any additional treatment.     

Developing a Nano‐Biosensor for DNA Hybridization Using a New Electroactive Label

Development of electrochemical DNA hybridization biosensors based on carbon paste electrode (CPE) and gold nanoparticle modified carbon paste electrode (NGMCPE) as transducers and ethyl green (EG) as a new electroactive label is described. Electrochemical impedance spectroscopy and cyclic voltammetry techniques were applied for the investigation and comparison of bare CPE and NGMCPE surfaces. Our voltammetric and spectroscopic studies showed gold nanoparticles are enable to facilitate electron transfer between the accumulated label on DNA probe modified electrode and electrode surface and enhance the electrical signals and lead to an improved detection limit. The immobilization of a 15‐mer single strand oligonucleotide probe on the working electrodes and hybridization event between the probe and its complementary sequence as a target were investigated by differential pulse voltammetry (DPV) responses of the EG accumulated on the electrodes. The effects of some experimental variables on the performance of the biosensors were investigated and optimum conditions were suggested. The selectivity of the biosensors was studied using some non‐complementary oligonucleotides. Finally the detection limits were calculated as 1.35×10^?10 mol/L and 5.16×10^?11 mol/L on the CPE and NEGCPE, respectively. In addition, the biosensors exhibited a good selectivity, reproducibility and stability for the determination of DNA sequences.     

CuO nanoparticles: An efficient and recyclable nanocatalyst for the rapid and green synthesis of 3,4-dihydropyrano[c]chromenes

Copper oxide nanoparticles showed excellent catalytic activity through three-component condensation reaction of aldehydes, malononitrile, and 4-hydroxycoumarin for the synthesis of 3,4-dihyropyrano[c]chromenes in water medium in excellent yields and very short reaction times.     

Conversion of carbon dioxide to valuable petrochemicals:An approach to clean development mechanism

The increase of atmospheric carbon dioxide and the global warming due to its greenhouse effect resulted in worldwide concerns. On the other hand, carbon dioxide might be considered as a valuable and renewable carbon source. One approach to reduce carbon dioxide emissions could be its capture and recycle via transformation into chemicals using the technologies in C1 chemistry. Despite its great interest, there are difficulties in CO2 separation on the one hand, and thermodynamic stability of carbon dioxide molecule rendering its chemical activity low on the other hand. Carbon dioxide has been already used in petrochemical industries for production of limited chemicals such as urea. The utilization of carbon dioxide does not necessarily involve development of new processes, and in certain processes such as methanol synthesis and methane steam reforming, addition of CO2 into the feed results in its utilization and increases carbon efficiency. In other cases, modifications in catalyst and/or processes, or even new catalysts and processes, are necessary. In either case, catalysis plays a crucial role in carbon dioxide conversion and effective catalysts are required for commercial realization of the related processes. Technologies for CO2 utilization are emerging after many years of research and development efforts.     

Aluminium Nitrate Nonahydrate (Al(NO3)3⋅9 H2O): An Efficient Oxidant Catalyst for the One‐Pot Synthesis of Biginelli Compounds from Benzyl Alcohols

A clean and efficient tandem oxidative cyclocondensation process is reported for the synthesis of 3,4‐dihydropyrimidin‐2(1H)‐one or ‐thione derivatives from primary aryl alcohols, β‐keto esters, and urea or thiourea in the presence of Al(NO₃)₃?9 H₂O as oxidant catalyst (Scheme, Table 5).     

Investigation into the potential ability of Pickering emulsions (food-grade particles) to enhance the oxidative stability of oil-in-water emulsions

In this study the potential ability of food-grade particles (at the droplet interface) to enhance the oxidative stability was investigated. Sunflower oil-in-water emulsions (20%), stabilised solely by food-grade particles (Microcrystalline cellulose (MCC) and modified starch (MS)), were produced under different processing conditions and their physicochemical properties were studied over time. Data on droplet size, surface charge, creaming index and oxidative stability were obtained. Increasing the food-grade particle concentration from 0.1% to 2.5% was found to decrease droplet size, enhance the physical stability of emulsions and reduce the lipid oxidation rate due to the formation of a thicker interfacial layer around the oil droplets. It was further shown that, MCC particles were able to reduce the lipid oxidation rate more effectively than MS particles. This was attributed to their ability to scavenge free radicals, through their negative charge, and form thicker interfacial layers around oil droplets due to the particles size differences. The present study demonstrates that the manipulation of emulsions' interfacial microstructure, based on the formation of a thick interface around the oil droplets by food-grade particles (Pickering emulsions), is an effective approach to slow down lipid oxidation.     

Approaches to the construction of substituted 4-amino-1H-pyrrol-2(5H)-ones

Fully substituted 4-aminopyrrolones are easily accessed via simple routes starting from imines, ketones, or α-bromophenyl acetonitriles. Imines were reacted with KCN/NH(4)Cl in aqueous ethanol to produce α-arylamino benzyl cyanides. On the other hand, ketones were transformed to the desired α-amino nitriles using a modified Strecker reaction. Then, α-amino nitrile precursors were allowed to react with a suitable acyl halide to produce the corresponding amides. Further treatment of these amides with ethanolic KOH converted them to highly substituted 4-amino-1H-pyrrol-2(5H)-one derivatives in moderate to excellent yields.     

A novel sensor for simultaneous determination of dopamine and uric acid using a new MFI-type zeolite prepared by microwave-assisted synthesis

Abstract  

This paper describes microwave-assisted synthesis of a new MFI-type zeolite, Zeolite Secony Mobile (ZSM-5), its characterization by X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM), and its application for fabrication of a modified carbon paste electrode. This novel electrode was employed for sensitive and simultaneous determination of dopamine and uric acid at biological pH (pH 7.0). The results show that this zeolite-modified carbon paste electrode significantly improves the electron transfer rate and reduces the overpotential of dopamine and uric acid oxidation without any fouling effect due to deposition of their oxidized products. The linear analytical curves were obtained in the ranges of 9.0 × 10⁻⁶–4.9 × 10⁻⁴ and 8.0 × 10⁻⁶–9.0 × 10⁻⁴ M for dopamine and uric acid, respectively, by using differential pulse voltammetry based on oxidation of these biomolecules. The detection limits (2σ) were determined for dopamine and uric acid as 7.9 × 10⁻⁶ and 7.1 × 10⁻⁶ M, respectively. This method has been successfully employed for quantification of dopamine and uric acid in real samples.     

Comparative study on the antioxidant activities of the different extracts and the composition of the oil extracted by n-hexane from Iranian Vitex pseudo-negundo

Antioxidant activities of different extracts obtained from the aerial parts of Vitex pseudo-negundo from Kashan, central Iran, were evaluated for the first time in this study using β-carotene/linoleic acid and scavenging of free-radical (DPPH) assays. Water extract showed the highest activity in both assays. GC-MS analysis of the oil extracted by n-hexane revealed 46 compounds with trans-β-farnesene being the main component. Several new compounds, not reported in the previous literature, were identified in the essential oil of this chemo-type.