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991.
D. Amin K. Y. Saleem 《International journal of environmental analytical chemistry》2013,93(3-4):275-278
Abstract A simple, rapid and sensitive titrimetric method with amplification has been worked out for the determination of 50–2000μg of o-cresol, m-cresol or p-cresol. It is based on bromination of these compounds with bromine water to form the corresponding hypobromites, which liberate an equivalent amount of iodine when treated with iodide. The sensitivity of the method has been increased using the Leipert amplification procedure. The coefficient of variation does not exceed 1.5% for above 500μg of the cresol, but increases to 2.2% at the 50μg-level. 相似文献
992.
Iraj Mohammadpoor-Baltork Hamid Reza Memarian Kiumars Bahrami 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):2315-2321
A variety of aliphatic, aromatic, and heteroaromatic thiols were rapidly and cleanly converted to their corresponding disulfides in excellent yields using n-butyltriphenylphosphonium dichromate (BTPPDC) in acetonitrile solution under solvent-free conditions and microwave irradiation. Selective oxidation of thiols in the presence of other oxidizable functional groups, such as alcohol and sulfide, is a noteworthy advantage of this method. 相似文献
993.
N‐Nitrosation of different types of secondary amines has been proceeded using supported perchloric acid on silica gel and sodiume nitrite under heterogeneous conditions. The operational system is simple and high pure products can be easily isolated with good to high yields. 相似文献
994.
Tautomeric mixtures of 4-aryl substituted 5-acetyl-2-methoxydihydropyrimidines undergo oxidation by exposing to the UV-light under formation of sole pyrimidines. The nature of the 4-substitution and solvent, and the ratio of tautomeric mixtures affect the rate of reaction. A proposed electron transfer-induced photo-dehydrogenation supports the obtained results in this study. 相似文献
995.
Hassan Valizadeh F. Mahmoodi Kordi Hamid Gholipur Mohammad Amiri 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):3075-3081
Phosphoric acid imidazolium dihydrogenphosphate was found to work well as a catalyst and excellent reaction medium in the Pechmann condensation of substituted phenols or α-naphthol with ethyl acetoacetate to give 4-methyl coumarins under microwave irradiation. This method is simple, cost effective, requires short reaction times, and gives very good to excellent yields. 相似文献
996.
Mohammad Reza Ganjali Hamid Reza Sobhi Hadi Farahani Parviz Norouzi Rassoul Dinarvand Amir Kashtiaray 《Journal of chromatography. A》2010,1217(16):2337-2341
Solid drop based liquid-phase microextraction (SDLPME) is a novel sample preparation technique possessing obvious advantages of simple operation with a high pre-concentration factor, low cost and low consumption of organic solvent. SDLPME coupled with gas chromatography (GC), high-performance liquid chromatography (HPLC), and atomic absorption spectrometry (AAS) has been widely applied to the analyses of a different variety of samples. The basic principles, parameters affecting the extraction efficiency, and the latest applications of SDLPME are reviewed in this article. 相似文献
997.
The octane number is one of the characteristics of spark-ignition fuels such as gasoline. Octane number of fuels can be improved by addition of oxygenates such as ethanol, MTBE (methyl tert-butyl ether), TBF (tertiary butyl formate) and TBA (tertiary butyl alcohol) as well as their blends with gasoline that reduce the cost impact of fuels. Carbon nanotubes (CNTs) are as useful additives for increasing the octane number. Functionalized carbon nanotubes containing amide groups have a high reactivity and can react with many chemicals. These compounds can be solubilized in gasoline to increase the octane number. In this study, using octadecylamine and dodecylamine, CNTs were amidated and the amino-functionalized carbon nanotubes were added to gasoline. Research octane number analysis showed that these additives increase octane number of the desired samples. X-ray diffraction (XRD), Fourier transforms infrared (FTIR), X-ray photoelectron spectroscopy (XPS), and thermal gravimetry analyses (TGA) were used for characterization of the prepared functionalized carbon nanotubes. 相似文献
998.
A new modified carbon paste electrode based on multi-walled carbon nanotubes and a synthesized Schiff base of N,N'-bis(2-hydroxybenzylidene)-2,2'(aminophenylthio) ethane, acting as a chelating agent for Ag(I) ions, is described. The electroanalytical procedure for the determination of Ag(I) was comprised of two steps: the chemical accumulation of the analyte under open-circuit conditions followed by replacing the medium with a 0.1 M HCl solution where the accumulated Ag(I) was reduced for 20 s in -0.7 V. The potential was then scanned from -0.2 to +0.2 V to obtain the voltammetric peak. The effective parameters in the sensor response were examined. Under optimized operational conditions, a linear response range from 0.5-200 ng mL(-1) was obtained. The detection limit for silver determination was 0.092 ng mL(-1). For 7 successive determinations of 15.0 and 60.0 ng mL(-1) of Ag(I), relative standard deviations of 2.2% and 1.2% were obtained, respectively. The procedure was applied in determining Ag(I) in X-ray photographic films and water samples. 相似文献
999.
Mehdi Adib Ehsan Sheikhi Morteza Karimzadeh Hamid Reza Bijanzadeh Massoud Amanlou 《Helvetica chimica acta》2012,95(5):788-794
A simple synthesis of N2‐alkyl‐N3‐[2‐(1,3,4‐oxadiazol‐2‐yl)aryl]benzofuran‐2,3‐diamines 5 via a one‐pot four‐component reaction is described (Scheme 1). A mixture of N‐(isocyanoimino)triphenylphosphorane ( 1 ), a 2‐aminobenzoic acid 2 , a 2‐hydroxybenzaldehyde 3 , and an isocyanide 4 in absolute EtOH at room temperature undergoes a smooth reaction to afford 5 in excellent yields (Table). 相似文献
1000.
Bahram Ghalami‐Choobar Hamid Dezhampanah Paria Nikparsa Ali Ghiami‐Shomami 《International journal of quantum chemistry》2012,112(10):2275-2280
In this work, calculations of pKa values have been performed on benzoic acid and its para‐substituted derivatives and some drugs by using Gaussian 98 software package. Gas‐phase energies were calculated with HF/6‐31 G** and B3LYP/6‐31 G** levels of theory. Free energies of solvation have been computed using the polarizable continuum model (PCM), conductor‐like PCM (CPCM), and the integral equation formalism‐PCM at the same levels which have been used for geometry determination in the gas‐phase. The results that show the calculated pKa values using the B3LYP are better than those using the corresponding HF. In comparison to the other models, the results obtained indicate that the PCM model is a suitable solvation model for calculating pKa values. For the investigated compounds, a good agreement between the experimental and the calculated pKa values was also observed. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 相似文献