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941.
Alireza Salimi Beni Maryam Zarandi Akram Hashemi Behzad Hosseinzadeh Alireza Najafi Chermahini 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2018,92(1):99-110
In this work a detailed quantum-chemical comparison of the relative stability of six tautomers of 1,2,5-oxadiazol-4,3-diamine studied in the gas phase and solution. Theoretical calculations are carried out by the density functional theory (DFT/B3LYP) and MP2 methods using the standard 311++G(d,p) basis set. The results indicate that A is the most stable form in the gas phase and also is the predominant tautomer in solution at the DFT and MP2 methods. The transition states of proton transfer reaction are calculated. The variation of dipole moments and charges on atoms are studied in various solvent. Specific solvent effects with addition of one water molecule near the electrophilic centers of tautomer investigated. Also the transition state of proton transfer assisted by a water molecule was investigated. 相似文献
942.
943.
An efficient approach toward C–H bond activation using iodine-mediated sp3C–H bond functionalization for the synthesis of dialkyl 3-(quinolin-2-yl)indolizine-1,2-dicarboxylates and dialkyl 3-(quinolin-2-yl)pyrrolo[2,1-a]isoquinoline-1,2-dicarboxylates through 1,3-dipolar cycloaddition reaction of nitrogen ylides with acetylenic esters is described. 相似文献
944.
Maryam Maleki Seyed Meysam Baghbanian Mahmood Tajbakhsh 《Journal of the Iranian Chemical Society》2018,15(2):359-368
A new magnetic oxidation catalyst was prepared using immobilization of tungstophosphoric acid on poly(N-vinylimidazole) entrapped magnetic nanozeolite and characterized by FTIR, TGA, XRD, SEM, TEM, EDX, VSM, and ICP-OES. The resulting heterogeneous catalyst displays high catalytic performance for selective oxidation of alcohols compared to the other catalysts. The catalyst could be reused eight times without any loss of catalytic activity. 相似文献
945.
Second-order standard addition for deconvolution and quantification of fatty acids of fish oil using GC-MS 总被引:1,自引:0,他引:1
In the present work two second-order calibration methods, generalized rank annihilation method (GRAM) and multivariate curve resolution-alternating least square (MCR-ALS) have been applied on standard addition data matrices obtained by gas chromatography-mass spectrometry (GC-MS) to characterize and quantify four unsaturated fatty acids cis-9-hexadecenoic acid (C16:1ω7c), cis-9-octadecenoic acid (C18:1ω9c), cis-11-eicosenoic acid (C20:1ω9) and cis-13-docosenoic acid (C22:1ω9) in fish oil considering matrix interferences. With these methods, the area does not need to be directly measured and predictions are more accurate. Because of non-trilinear conditions of GC-MS data matrices, at first MCR-ALS and GRAM have been used on uncorrected data matrices. In comparison to MCR-ALS, biased and imprecise concentrations (%R.S.D. = 27.3) were obtained using GRAM without correcting the retention time-shift. As trilinearity is the essential requirement for implementing GRAM, the data need to be corrected. Multivariate rank alignment objectively corrects the run-to-run retention time variations between sample GC-MS data matrix and a standard addition GC-MS data matrix. Then, two second-order algorithms have been compared with each other. The above algorithms provided similar mean predictions, pure concentrations and spectral profiles. The results validated using standard mass spectra of target compounds. In addition, some of the quantification results were compared with the concentration values obtained using the selected mass chromatograms. As in the case of strong peak-overlap and the matrix effect, the classical univariate method of determination of the area of the peaks of the analytes will fail, the “second-order advantage” has solved this problem successfully. 相似文献
946.
Shayessteh Dadfarnia Ali Mohammad Haji Shabani Fatema Tamadon Maryam Rezaei 《Mikrochimica acta》2007,158(1-2):159-163
A simple and rapid flow injection system is proposed for indirect determination of cyanide by flame atomic absorption spectrometry.
It consists of a microcolumn of immobilized salen (N,N′-bis(salicylidene)ethylenediamine) on sodium dodecyl sulfate (SDS)-coated
alumina saturated with silver ion and a carrier of dilute solution of sodium hydroxide (10−5 mol L−1). The micro-column was located between the injection valve and nebulizer of atomic absorption spectrometry. Injection of
250 μL of aqueous cyanide standard or sample solution at pH range of 9–11 cause elution of silver as silver cyanide complexes,
which was then measured by flame atomic absorption spectrometry. The absorbance was proportional to the concentration of cyanide
in the sample. The graph of absorbance (as peak height) vs. cyanide concentration was linear over the concentration range
of 0.1–10 mg L−1 of cyanide, and the detection limit was 0.06 mg L−1. The relative standard deviation at 1 and 3 mg L−1 of cyanide concentration were 4.1 and 4.7%, respectively. The method was successfully applied to determination of cyanide
in water and industrial waste waters, and the accuracy was examined through independent analysis by accepted method of pyridine-barbituric
acid. 相似文献
947.
Two new ZnII(μ‐4,4′‐bipy) coordination polymers with acetate anions, [Zn(4,4′‐bipy)(AcO)2] ( 1 ) and [Zn2(4,4′‐bipy)(AcO)4] ( 2 ), have been synthesized. The compounds were characterized with elemental analysis, IR‐, 1H NMR‐, 13C NMR spectroscopy and studied by thermal analysis, fluorescence measurements and x‐ray crystallography. The structural studies of compound 1 suggest the structure is a coordination polymer of zinc(II) consisting of linear double chains formed by bridging 4,4′‐bipy ligand and connection of the acetate‐bridged centrosymmetric [Zn2(OAc)2]2+ nodes. 相似文献
948.
949.
Majid M. Heravi Khadijeh Bakhtiari Tina Benmorad Fatemeh F. Bamoharram Hossein A. Oskooie Maryam H. Tehrani 《Monatshefte für Chemie / Chemical Monthly》2007,138(5):449-452
Summary. The nitration of aromatic compounds was carried out in the presence of divanadium-substituted molybdophosphoric acid, H5PMo10V2O40, as catalyst and a mixture of nitric acid and acetic anhydride as nitrating agent. In the presence of this heteropolyacid
the ortho- and para-nitro compounds were obtained in good to excellent yields under mild reaction conditions. 相似文献
950.
Issa Yavari Zinatossadat Hossaini Maryam Sabbaghan Majid Ghazanfarpour-Darjani 《Tetrahedron》2007,63(38):9423-9428
The reaction of ethyl propiolate with triphenylphosphine (Ph3P) in the presence of N-alkylisatins led to ethyl 2,2,2-triphenyl-2,5-dihydro-1,2-λ5-oxaphosphole-4-carboxylate-spiro-1-alkyl-1,3-dihydro-2H-indol-2-ones in good yield. The reaction of dialkyl acetylenedicarboxylates with Ph3P in the presence of N-alkylisatins led to dialkyl 2,2,2-triphenyl-2,5-dihydro-1,2-λ5-oxaphosphole-3,4-dicarboxylate-spiro-1-alkyl-1,3-dihydro-2H-indol-2-ones and alkyl 4-(alkoxy)-5-oxo-2,5-dihydro-3-furancarboxylate-spiro-1-alkyl-1,3-dihydro-2H-indol-2-ones. 相似文献