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191.
Jeong Hyun Kim Seung-Hyun Kang Il Nam Jung Kwan Mook Kim Bok Ryul Yoo Myong Euy Lee 《Journal of Sol-Gel Science and Technology》2004,32(1-3):31-35
Reaction of (triphenylmethyl)silanetriol (1) with cyclopentadienyltitanium trichloride (CpTiCl3) in the presence of triethylamine as a HCl scavenger gave both compounds of a partial open-cage type {[Ph3CSiO(OH)]3(Ph3CSiO3/2)(CpTiO3/2)4} (2) and cube type (Ph3CSiO3/2CpTiO3/2)4 (3). The 1:1 reaction of 1 and CpTiCl3 in toluene solvent at reflux temperature for 3 d afforded compounds 2 (22%) and 3 (36%). When 1 is reacted with a 1.5 fold excess of CpTiCl3 under the same conditions, compound 3 was obtained in high yield (81%) along with 2 in trace quantities. Compounds 2 and 3 were fully characterized by the analyses of 1H, 13C, 29Si NMR, IR, and FAB MS data. The solid-state structure of 3 was determined by a single crystal X-ray diffraction study. Compound 3 had shown to have catalytic activity for the oxidation of alkenes such as 1-octene, cyclooctene, and norbornene with t-butyl hydrogen peroxide. The effect of solvent was observed in this epoxidation reaction. The order of reactivity were decreased as follows: CHCl3 > hexane THF. 相似文献
192.
John D. Van Dyke Kim L. Kasperski 《Journal of polymer science. Part A, Polymer chemistry》1993,31(7):1807-1823
Dried samples of polyacrylamide in an He atmosphere have been subjected to thermogravimetric analysis in the 30–600°C range, and the evolved gases were monitored by FTIR. Water, ammonia, and small quantities of carbon dioxide are released in the first stages of decomposition (220–340°C), where the polymer chains remain intact and the reaction occurs on the pendant amide groups. In the second stage of decomposition (340–440°C), the majority of the weight loss occurs, and main chain breakdown occurs, releasing carbon dioxide, water, nitrile compounds, and imides. Trapping of the gases in this stage and analysis by GC–FTIR and GC–MS reveals the presence of more than 20 decomposition products, and confirms that a large proportion of these can be assigned to glutarimide and its substituted analogs. Imidization and dehydration reactions on the amide groups, as well as free radical breakdown of the main chains, with inter- and intramolecular hydrogen transfer, can account for many of the products of the decomposition. © 1993 John Wiley & Sons, Inc. 相似文献
193.
By means of differential pulse polarography, Pu ions of different oxidation states have been investigated in 1M Na2CO3 solution. Redox reactions of Pu/III/, Pu/IV/, Pu/V/ and Pu/VI/, which are mostly of irreversible nature, have been observed within the potential range of the dropping mercury electrode /DME/, from 0 to –1.5 V, against a Ag/AgCl/NaCl (3M) reference electrode. Based on the peak potential observed for each reaction, the stability of a given oxidation state in the solution could be ascertained. The redox potential of the Pu/IV/–Pu/III/ pair, which was found to be –1.0 V, indicated that the Pu/IV/ carbonate complex was of high stability. The detection sensitivity of the Pu/IV/ ion was found to be 1×10–6M. 相似文献
194.
S. H. Kim Eli M. Pearce T. K. Kwei 《Journal of polymer science. Part A, Polymer chemistry》1993,31(13):3167-3180
The precursor of polybenzimidazole (PBI), poly(3,3′-diamino-4,4′-benzidine isophthalamide) (PDABI), was synthesized from poly(3,3′-dinitro-4,4′-benzidine isophthalamide) (PDNBI) by reduction. With increasing temperature, the NH2 moiety which was protected by SnCl5?1 could cyclize and form PBI. Blends with polyamic acid (LaRC-TPI) were prepared. Clear blend films were prepared at up to 400°C. The IR spectra displayed shifts in the NH stretching band, thereby providing evidence for specific interactions related to the miscibility of their cured blends. © 1993 John Wiley & Sons, Inc. 相似文献
195.
The following pyrethrin and pyrethroid pesticides were determined in urine and water matrixes by liquid chromatography with diode array detection (LC-DAD): pyrethrin I, pyrethrin II, tetramethrin, baythroid, bifenthrin, fenvalerate, phenothrin, allethrin, resmethrin, cis-permethrin, and trans-permethrin. In addition, 3-phenoxybenzyl alcohol, a metabolite of various pyrethroids, was also successfully determined by the analytical method. The matrix extraction was simple, inexpensive, and fast, using only sodium chloride and acetonitrile. The acetonitrile extract was filtered and analyzed by LC-DAD. The method detection limits for the pyrethrin pesticides in 5 mL urine were determined to range from 0.002 to 0.04 microg/mL, depending on the individual pyrethrin. Recoveries from spiked tap water ranged from 77 to 96%; recoveries from urine ranged from 80 to 117%. This method is especially well-suited to clinical investigations, in which rapid analysis of forensic samples is often required. 相似文献
196.
Byeong Hyo Kim Rongbi HanFengyu Piao Young Moo JunWoonphil Baik Byung Min Lee 《Tetrahedron letters》2003,44(1):77-79
N-Arylacetamides were prepared in excellent yields from nitroarenes in the presence of acetic anhydride, acetic acid and indium by a one-pot procedure. 相似文献
197.
Ju-Won Tae Byung-Sik Jang Kyung-Hoon Kim Dae-Won Park 《Reaction Kinetics and Catalysis Letters》2005,84(1):167-174
Summary The addition of carbon dioxide to phenyl glycidyl ether (PGE) was investigated in a semi-batch reactor using immobilized quaternary ammonium chloride catalysts. Five different catalysts were prepared with the following supports : (1) soluble poly(ST-<Emphasis Type=Italic>co</Emphasis>-VBC) [C1], (2) insoluble poly(ST-DVB-VBC) [C2], (3) macroporous poly(ST-DVB-VBC) [C3], (4) poly(ST-<Emphasis Type=Italic>co</Emphasis>-VBC)-MMT [C4] (5) modified MCM-41 [C5]. The addition of carbon dioxide to PGE can be considered as a pseudo-first order process with respect to the concentration of PGE. The pseudo-first order rate constant for the catalysts decreased in the series C1>C3>C2>C4>C5. The activation energy for C1 to C5 catalysts was 8.6, 20.9, 19.9, 23.9, and 26.8 kJ/mol, respectively. The immobilized catalysts can be reused in least 4 successive runs without any considerable loss of their initial reactivities. 相似文献
198.
DeClue MS Baldridge KK Künzler DE Kast P Hilvert D 《Journal of the American Chemical Society》2005,127(43):15002-15003
Isochorismate pyruvate lyase (IPL) catalyzes the cleavage of isochorismate to give salicylate and pyruvate, a key step in bacterial siderophore biosynthesis. We investigated the enzyme from Pseudomonas aeruginosa using isochorismate selectively deuterated at C2 as a substrate. Monitoring the reaction by 2H NMR spectroscopy revealed that the label is quantitatively transferred from C2 to C9, producing stoichiometric amounts of [3-2H]pyruvate as product. Moreover, the deuterium kinetic isotope effect of 2.34 +/- 0.08 on kcat indicates that C-H cleavage is significantly rate limiting. Consistent with these data, hybrid density functional theory (HDFT) calculations at the Becke3LYP/DZ+(2d,p) level of theory predict a concerted but highly asynchronous pericyclic transition structure, in which carbon-oxygen bond cleavage is more advanced than hydrogen atom transfer from C2 to C9; the calculated 2H isotope effect of 2.22 at C2 is in excellent accord with the experimental value. Together, these findings indicate that IPL should be added to the small set of proteins that are known to catalyze pericyclic reactions. They also raise the possibility that enzymes, such as chorismate pyruvate lyase, salicylate synthase, 4-amino-4-deoxychorismate lyase, and anthranilate synthase, which accelerate formally similar reaction steps, may also exploit pericyclic mechanisms. 相似文献
199.
An unusually stable molecular capsule was formed by heating phenyleneurea-spanned resorcinarene cavitand with 4-methyl-N-p-tolylbenzamide. The molecular capsule behaved as a discrete molecular entity showing a cylindrical D(4d) structure and showed no guest exchange in toluene-d(8) even at 100 degrees C. [structure: see text] 相似文献
200.
The direct enantioseparation of a novel aminothiazolecarboxamide fungicide, ethaboxam, on polysaccharide-derived chiral stationary phases (CSPs) is described. Good resolution is achieved with several polysaccharide-derived CSPs. Chiralcel OD (OD-H) and Chiralpak AS are excellent for direct enantiomer separation of ethaboxam. The elution behavior and the effects of eluent composition on the resolution of ethaboxam are also investigated. Furthermore, the mechanism for chiral recognition using molecular mechanics is discussed. 相似文献