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981.
Orugunty RS Ghiviriga I Abboud KA Battiste MA Wright DL 《The Journal of organic chemistry》2004,69(2):570-572
The reaction of tetrabromocyclopropene and furan leads directly to 8-oxabicyclo[3.2.1]octadiene derivatives. It has been proposed that this involves an initial Diels-Alder reaction followed by rearrangement of the primary adduct. We have, for the first time, isolated a primary adduct and established through X-ray crystallographic analysis that the adduct is the product of an exo-selective addition. Kinetic studies suggest the intermediacy of charged intermediates during the rearrangement. 相似文献
982.
Cai X Zhai Y Ghiviriga I Abboud KA Dolbier WR 《The Journal of organic chemistry》2004,69(12):4210-4215
The sequential reaction of 2 equiv of difluorocarbene (generated from trimethylsilyl fluorosulfonyldifluoroacetate (TFDA) by treatment with catalytic fluoride ion) with a series of electron-rich aromatic ketones and alpha,beta-unsaturated ketones leads to the formation of difluoromethyl 2,2-difluorocyclopropyl ethers in good yield. 相似文献
983.
This article has been retracted at the request of the Talanta Editors-in-Chief.Reason: After publication this article was discovered to have been plagiarized from an earlier work by Orlando Fatibello-Filho, Marcos Fernando de Souza Teixeira, Alexandre Zambon Pinto, presented in their paper ‘Coated graphite-epoxy ion-selective electrode for the determination of iron(III) in oxalic medium’, published in Analytical Letters 30 (1997) 417-427.We very much regret this error, and offer our apologies to Professor Fatibello-Filho and his co-workers.J-M. KauffmannG.D. ChristianEditors-in-Chief 相似文献
984.
A series of [W(CO)4]2(-dppa)(-DTA) type complexes [dppa = Ph2P(CH2)
n
PPh2, n = 2(dppe), 4(dppb), 6(dpph), 10(dppd); DTA =
t
BuS(CH2)
m
S
t
Bu, m = 3(DTN), 4(DTD), 5(DTUD), 6(DTDD)] containing doubly bridged bisphosphine and dithiaalkane ligands have been prepared by stepwise replacement of piperidine (pip) from cis-W(CO)4(pip)2 complex. In addition, complexes of general formulae [W(CO)4]2(-dppa)2 and [Mo(CO)4]2(-DTA)2 have been prepared by similar methods. These new complexes have been characterized by i.r. spectroscopy and elemental analysis. 相似文献
985.
A mesoporous silica gel Davidson 59 was thermally treated in vacuo, in the temperature range 20–1000°C. Effects of thermal treatment on the water contents, nitrogen surface areas, pore structure and heats of immersion in water were investigated and discussed. The temperatures selected were 20, 110, 200, 290, 380, 480, 510 and 1000°C. These temperatures were found to cover all the various textural changes resulting from the heat effect.It could be shown that the heats of immersion in water depend primarily on the water content of the sample and are proportional, at least qualitatively to the number of hydroxyl groups on the surface and their availability for interaction with liquid water. The interesting result obtained is that a second factors is involved, namely the pore structure of the adsorbent. A qualitative parallelism exists between the normalized heat of immersion per unit area, and the average pore radius. Apparently the packing of water molecules in narrow pores leads to a decrease in the heat of immersion due to repulsion between the permanent dipoles of the molecules. In narrower pores, the heat of immersion in water is smaller than in wide pores. 相似文献
986.
Sun YK Myung ST Kim MH Prakash J Amine K 《Journal of the American Chemical Society》2005,127(38):13411-13418
The high capacity of Ni-rich Li[Ni(1-x)M(x)]O(2) (M = Co, Mn) is very attractive, if the structural instability and thermal properties are improved. Li[Ni(0.5)Mn(0.5)]O(2) has good thermal and structural stabilities, but it has a low capacity and rate capability relative to the Ni-rich Li[Ni(1-x)M(x)]O(2). We synthesized a spherical core-shell structure with a high capacity (from the Li[Ni(0.8)Co(0.1)Mn(0.1)]O(2) core) and a good thermal stability (from the Li[Ni(0.5)Mn(0.5)]O(2) shell). This report is about the microscale spherical core-shell structure, that is, Li[Ni(0.8)Co(0.1)Mn(0.1)]O(2) as the core and a Li[Ni(0.5)Mn(0.5)]O(2) as the shell. A high capacity was delivered from the Li[Ni(0.8)Co(0.1)Mn(0.1)]O(2) core, and a high thermal stability was achieved by the Li[Ni(0.5)Mn(0.5)]O(2) shell. The core-shell structured Li[(Ni(0.8)Co(0.1)Mn(0.1))(0.8)(Ni(0.5)Mn(0.5))(0.2)]O(2)/carbon cell had a superior cyclability and thermal stability relative to the Li[Ni(0.8)Co(0.1)Mn(0.1)]O(2) at the 1 C rate for 500 cycles. The core-shell structured Li[(Ni(0.8)Co(0.1)Mn(0.1))(0.8)(Ni(0.5)Mn(0.5))(0.2)]O(2) as a new positive electrode material is a significant breakthrough in the development of high-capacity lithium batteries. 相似文献
987.
Reactions of the intermediate W(CO)5THF, generated photochemically from W(CO)6 in THF, with Ph2P(CH2)
n
PPh2 [ = PP; n = 2 (dppe), 4 (dppb), 6 (dpph), 10 (dppd)] at room temperature in THF solutions gave exclusively bimetallic complexes of the (CO)5WPPW(CO)5 type. In addition, complexes bridged by diphosphine ligands of the (CO)4(pip)MPPM(pip)(CO)4 type (pip = piperidine; M = Mo, W) were prepared by stirring the (CO)4M(pip)2 complexes with bis(diphenylphosphino)alkanes in CH2Cl2 solution at ambient temperatures. These new bis(diphenylphosphino)alkane-bridged complexes were characterized by i.r., 1H- and 31P-n.m.r. spectroscopies, as well as by elemental analysis. 相似文献
988.
Sustainable existence of solid mercury (Hg) nanoparticles at room temperature and their applications
Villa Krishna Harika Tirupathi Rao Penki Boddapati Loukya Atanu Samanta Gui-Liang Xu Cheng-Jun Sun Ilya Grinberg Francis Leonard Deepak Khalil Amine Doron Aurbach Aharon Gedanken 《Chemical science》2021,12(9):3226
Although liquid mercury (Hg) has been known since antiquity, the formation of stable solid nano forms of Hg at room temperature has not been reported so far. Here, for the first time, we report a simple sonochemical route to obtain solid mercury nanoparticles, stabilized by reduced graphene oxide at ambient conditions. The as-formed solid Hg nanoparticles were found to exhibit remarkable rhombohedral morphology and crystallinity at room temperature. Extensive characterization using various physicochemical techniques revealed the unique properties of the solid nanoparticles of Hg compared to its bulk liquid metal phase. Furthermore, the solid nature of the Hg nanoparticles was studied electrochemically, revealing distinctive properties. We believe that solid Hg nanoparticles have the potential for important applications in the fields of electroanalytical chemistry and electrocatalysis.Formation of the stable solid mercury nanoparticles by acoustic cavitation and their electrochemical activity compared to its bulk liquid metal. 相似文献
989.
Christensen NK Bryld T Sørensen MD Arar K Wengel J Nielsen P 《Chemical communications (Cambridge, England)》2004,(3):282-283
Two LNA (locked nucleic acid) stereoisomers (beta-L-LNA and alpha-D-LNA) are evaluated in the mirror-image world, that is by the study of two mixed sequences of LNA and alpha-L-LNA and their L-DNA and L-RNA complements. Both are found to display high-affinity RNA-recognition by the formation of duplexes with parallel strand orientation. 相似文献
990.
Composite ceria/silica materials of 10 and 20% (w/w) were prepared by calcination, at 650 degrees C for 3 h, of the xerogels obtained by mixing the corresponding amount of a ceria precursor with freshly prepared sols of spherical silica particles (Stober particles) in their mother liquors. Two different ceria precursors were examined in this investigation. The first was a gel produced by the prehydrolysis of cerium(IV) isopropoxide in isopropanol medium, and the second was an aqueous solution of cerium(IV) ammonium nitrate. Different textural and morphological characteristics that developed by calcination were investigated by TGA, FTIR, XRD, SEM, and analyses of N2 adsorption isotherms. The results indicated that ceria dispersion and formation of mesoporous textural composite materials produced by the second precursor, cerium(IV) ammonium nitrate, are better than those produced by the first precursor, prehydrolyzed cerium(IV) isopropoxide. The results are discussed in terms of the effect of precursors and mixing media on nucleation and growth of ceria particles and their protection from sintering on calcination at the test temperature. 相似文献