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41.
Mustafa R. Ibrahim Zacharia A. Fataftah Paul von Ragu Schleyer Peter D. Stout 《Journal of computational chemistry》1987,8(8):1131-1138
Sets of hydrogen molecule equivalents have been developed which permit the calculation of hydrogenation of different types of carbon-carbon bonds from ab initio total energies (3-21G and 6-31G* basis sets, and, to a more limited extent, for MP2/6-31G* data) of reactants and products. The calculated enthalpies of hydrogenation are in good agreement with experiment for unstrained molecules, with average errors on the order of 2 kcal/mol. The 6-31G* equivalents allow the enthalpies for strained molecules to be calculated accurately, but the 3-21G equivalents do not. The equivalents for both basis sets have been tested by calculating the enthalpies of hydrogenation of carbon-carbon bonds in nitrogen- and oxygen-containing organic molecules, free radicals, and classical carbocations. The results are in good agreement with experiment in most cases. 相似文献
42.
Arzu
zek idem Albayrak Mustafa Odabaolu Orhan Büyükgüngr 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(3):o177-o180
The title compounds, (E)‐2‐[(2‐bromophenyl)iminomethyl]‐4‐methoxyphenol, C14H12BrNO2, (I), (E)‐2‐[(3‐bromophenyl)iminomethyl]‐4‐methoxyphenol, C14H12BrNO2, (II), and (E)‐2‐[(4‐bromophenyl)iminomethyl]‐4‐methoxyphenol, C14H12BrNO2, (III), adopt the phenol–imine tautomeric form. In all three structures, there are strong intramolecular O—H⋯N hydrogen bonds. Compound (I) has strong intermolecular hydrogen bonds, while compound (III) has weak intermolecular hydrogen bonds. In addition to these intermolecular interactions, C—H⋯π interactions in (I) and (III), and π–π interactions in (I), play roles in the crystal packing. The dihedral angles between the aromatic rings are 15.34 (12), 6.1 (3) and 39.2 (14)° for (I), (II) and (III), respectively. 相似文献
43.
A simple solid phase extraction procedure for speciation of selenium(IV) and selenium(VI) in environmental samples has been proposed prior to graphite furnace atomic absorption spectrometry. The method is based on the solid phase extraction of the selenium(IV)-ammonium pyrrolidine dithiocarbamate (APDC) chelate on the Diaion HP-2MG. After reduction of Se(VI) by heating the samples in the microwave oven with 4 mol l−1 HCl, the system was applied to the total selenium. Se(VI) was calculated as the difference between the total selenium content and Se(IV) content. The experimental parameters, pH, amounts of reagents, eluent type and sample volume were optimized. The recoveries of analytes were found greater than 95%. No appreciable matrix effects were observed. The adsorption capacity of sorbent was 5.20 mg g−1 Se (IV). The detection limit of Se (IV) (3sigma, n = 11) is 0.010 μg l−1. The preconcentration factor for the presented system was 100. The proposed method was applied to the speciation of selenium(IV), selenium(VI) and determination of total selenium in natural waters and microwave digested soil, garlic, onion, rice, wheat and hazelnut samples harvested various locations in Turkey with satisfactory results. In order to verify the accuracy of the method, certified reference materials (NIST SRM 2711 Montana Soil, NIST SRM 1568a Rice Flour and NIST SRM 8418 Wheat Gluten) were analyzed and the results obtained were in good agreement with the certified values. The relative errors and relative standard deviations were below 6 and 10%, respectively. 相似文献
44.
Mustafa Yavuz 《高分子科学》2007,(4):347-355
Electrorheological (ER) properties of polyaniline (PAni), pumice and polyaniline/pumice composites (PAPC) were investigated. Polyaniline and PAni/pumice composite were prepared by oxidative polymerization. PAni/pumice particlesbased ER suspensions were prepared in silicone oil (SO), and their ER behavior was investigated as a function of shear rate, electric field strength, concentration and temperature. Sedimentation stabilities of suspensions were determined. It has been found that ER activity of all the suspensions increases with increasing electric field strength, concentration and decreasing shear rate. It has shown that the suspensions have a typical shear thinning non-Newtonian viscoelastic behavior. Yield stress of composite suspensions increased linearly with increasing applied electric field strength and with concentrations of the particles. The effect of high temperature on ER activity of purrfice/silicone oil systems was also investigated. 相似文献
45.
A squarate-based synthesis of 2-ferrocenylidene-4-cyclopentene-1,3-diones is described. When refluxed in dioxane at 100 °C, heated with silica gel as a solvent free grinded solid mixture at 125 °C or stirred with silica gel in ethyl acetate at room temperature, 4-ferrocenylethynyl-4-hydroxy-2-cyclobutenones, prepared from ethynylferrocene and 3-cyclobutene-1,2-diones, afforded 2-ferrocenylidene-4-cyclopentene-1,3-diones as the major or single product of the reaction. In some cases, ferrocenyl quinones also resulted from these reactions as the minor products. The major or exclusive formation of 2-ferrocenylidene-4-cyclopentene-1,3-diones is attributed to the radical-stabilizing ability of the ferrocenyl group. 相似文献
46.
Naki Çolak Yılmaz Yıldırır Mustafa Kavutcu Nilhan Nurlu 《Monatshefte für Chemie / Chemical Monthly》2007,138(12):1283-1287
Summary. Methotrexate (MTX) is a folate antagonist used in treatment of several chronic inflammatory and neoplastic conditions. In this study, new MTX-like compounds that may-be potential anticancer agents were synthesized and their structures were determined by IR, UV, GC-MS,
1H NMR, and 13C NMR spectra. Also, in this study, a series structurally related to MTX or folate analogous compounds were evaluated whether they have inhibitory properties on the dihydrofolate reductase activity
(DHFR). 相似文献
47.
Yusuf M. Al-Hiari Ali M. Qaisi Mustafa M. El-Abadelah Wolfgang Voelter 《Monatshefte für Chemie / Chemical Monthly》2006,137(2):243-248
Summary. A synthesis of 3-(4-methoxycarbonyl-2,6-dinitrophenyl)indole, its 2,6-diamino analog, and 3-(2-amino-4-trifluoromethyl-6-nitrophenyl)indole
is described. 4-(Trifluoromethyl)phenyl derivatives exhibit higher antibacterial potency than the former 4-(methoxycarbonyl)phenyl
homologs, while 3-(4-trifluoromethyl-2-nitrophenyl)indole was the most active agent in the series, with MIC ≈ 7 μg/cm3 against E. coli and S. aureus. 相似文献
48.
Nobuo Ishikawa Tomoya Kitazume Kunitake Chino Mohamed El-Said Mustafa 《Journal of fluorine chemistry》1981,18(4):447-457
The reactions of -2-methyl-2-pentene (1) with several - difunctional benzenes afforded eight- and nine-membered benzoheterocyclic compounds carrying perfluoroalkyl groups. Salicylic acid, salicylaldehyde, and their methyl or chloro derivatives reacted in triethylamine-acetonitrile system giving perfluoroalkylated 2H,6H-1,5-benzodioxocin-2,6-dione (8) and 4H,6H-1,5-benzodioxocin (9) compounds respectively, while phthalyl alcohol and o-hydroxyphenethyl alcohol in triethylamine-diethyl ether system gave perfluoroalkylated 1H,3H,7H-2,6- and 4H,6H,7H-1,5-benzodioxonin compounds, (10) and (11). o-Aminobenzyl alcohol and (1) in diethyl ether afforded a perfluoroalkylated benzoxazocinobenzoxazocinone compound (15). 相似文献
49.
Talal A. K. Al-Allaf Ihsan A. Mustafa Sa'ad E. Al-Mukhtar 《Transition Metal Chemistry》1993,18(1):1-5
Summary A series of new PtII and PdII complexes of N,N-disubstituted thiourea derivatives of general formulae [MLCl2]2, [ML2Cl2] and [ML4]Cl2 have been prepared and characterised by physicochemical and spectroscopic methods. The reaction of these ligands with [M(DMSO)2Cl2], M = Pt, cis- or Pd, trans-, in CHCl3 and EtOH at ambient temperature or under reflux, is described. 相似文献
50.
Khalid Mohammed Khan Ghulam Murtaza MaharviSafdar Hayat Zia-UllahM. Iqbal Choudhary Atta-ur-Rahman 《Tetrahedron》2003,59(29):5549-5554
Treatment of aromatic carboxylic acids and substituted toluenes with a mixture of sodium bromate and sodium hydrogen sulfite in a two-phase system gave the corresponding esters in good yield. The intermediate α-brominated toluene was formed by the in situ generated hypobromous acid. The α-bromotoluene underwent an intermolecular nucleophilic substitution reaction with aromatic carboxylic acids present in the reaction mixture to afford the corresponding esters. 相似文献