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81.
Structural investigations of thin films of SiC, SiC with free silicon and various titanium suicides (TiSi2, TiSi and Ti5Si3) are described. The crystal phases have been identified using X-ray diffractometry. The growth of reaction products from surface reactions between silicon and deposited titanium can be observed.Dedicated to Professor Dr. rer.nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday 相似文献
82.
Sucrose ethyleneoxide adducts have been prepared by reaction of sucrose with various amounts of ethyleneoxide inDMSO. The resulting polypode molecules were found to be efficient phase transfer catalysts in nucleophilic substitutions, oxidation and dichlorcarbene generation. Polymerisable polypodes have been obtained by reaction of sucrose ethyleneoxide adducts with methacrylic anhydride or methacryloylchloride in pyridine. Free radical polymerisation of the resulting mixtures of mono- and polyfunctional methacrylic esters of sucrose ethyleneoxide adducts yielded crosslinked gels. These polymer-supported octopus-molecules were found to be efficient triphase catalysts. 相似文献
83.
84.
Buckart S Ganteför G Kim YD Jena P 《Journal of the American Chemical Society》2003,125(46):14205-14209
The change in the electronic structure of Au(n)- clusters induced by the exchange of an Au atom by hydrogen is studied using photoelectron spectroscopy. Au anion clusters react with one hydrogen atom but not with molecular hydrogen. The spectra of Au(n)- and Au(n-1)H- clusters show almost identical features for n > 2 suggesting that hydrogen behaves as a protonated species by contributing one electron to the valence pool of the Au(n)- cluster. This behavior is in sharp contrast to that of the commonly understood electronic structure of hydrogen in metals; namely, it attracts an electron from the conduction band of the metal and remains in an "anionic" form or forms covalent bonding. We discuss the influence of the unique electronic structure of H on the unusual catalytic behavior of Au clusters. 相似文献
85.
The enol of acetone, formed by disproportionation reactions of 1-hydroxy-1-methylethyl radicals, is detected by NMR, spectroscopy during photoreactions of 3-hydroxy-3-methyl-2-butanone in acetonitrile and of acetone in 2-propanol and slowly tautomerizes to acetone. The photolysis of 3-hydroxy-3-methyl-2-butanone is shown to proceed via Type I cleavage, predominantly from an excited triplet state. 相似文献
86.
Alfred Fischer Michael W. Morgan Colin Eaborn 《Journal of organometallic chemistry》1977,136(3):323-332
Rates of cleavage of some picoyl- and (quinolylmethyl)-trimethylsilanes (RSiMe3, where R = PyCH2 or QnCH2SiMe3) have been measured in “90%” aqueous methanolic sodium methoxide at 50°C. Relative reactivities are: 2-PyCH2, 1.0; 3-PyCH2, 0.030; 4-PyCH2, 8.9; 2-QnCH2, 41; 3-QnCH2, 0.161; 4-QnCH2, 37. The rates correlate well with those for base-catalysed hydrogen-exchange in the parent carbon acids RH. Approximate pKa's (based on the scale of ion-pair acidities in CsNHC6H11H2NC6H11, with pKa of 9-phenylfluorene = 18.6) for the carbon acids, RH, can be derived as follows: 2-PyCH3, 29.5; 3-PyCH3, 34; 4-PyCH3, 27; 2-QnCH3, 25; 3-QnCH3, 32; 4-QnCH3, 25.Rates of cleavage of pyridyl- and quinolyl-trimethylsilanes (PySiMe3 and QnSiMe3) by sodium hydroxide in 4 : 1 v/v Me2SO/H2O at 50°C have also been measured; and the relative reactivities are: 2-Py, 1.0; 3-Py, 2.9; 4-Py, 8.4; 2-Qn, 15.9; 3-Qn, 12.7; 4-Qn, 184. The sequence of reactivity differes from that for base-catalysed hydrogen-exchange at the relevant positions of pyridine and quinoline, indicating that the reactivities are not determined in both cases (if in either) solely by the stabilities of the corresponding carbanions. 相似文献
87.
In many technical processes, complex multicomponent mixtures have to be handled, for example, in reaction or separation equipment. High-resolution NMR spectroscopy is an excellent tool to study these mixtures and gain insight in their behavior in the processes. For on-line studies under process conditions, flow NMR probes can be used in a wide range of temperature and pressure. A major challenge in engineering applications of NMR spectroscopy is the need for quantitative evaluation. Flow rates, recovery times, and other parameters of the on-line NMR experiments have to be optimized for this purpose. Since it is generally prohibitive to use deuterated solvents in engineering applications, suitable techniques for field homogenization and solvent signal suppression are needed. Two examples for the application of on-line NMR spectroscopic experiments in process engineering are presented, studies on chemical equilibria and reaction kinetics of the technically important system formaldehyde-water-methanol and investigations on reactive gas absorption of CO(2) in aqueous solutions of monoethanolamine. 相似文献
88.
Dan Veierov Tuvia Bercovici Ernst Fischer Yehuda Mazur Amnon Yogev 《Helvetica chimica acta》1975,58(4):1240-1243
Enol-esters 1a-1e undergo clean Photo-Fries-rearrangements without side reactions. With anthroyl derivatives the reaction is observed only at 254 nm, not at 366 nm. 相似文献
89.
Guibin Ma Andreas Fischer Julius Glaser 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(3):m177-m178
The title compound, bis(dimethyl sulfoxide)triiodothallium(III), [TlI3(C2H6OS)2], was crystallized from equimolar amounts of TlII and I2 in a dimethyl sulfoxide (DMSO) solution. After the initial redox reaction, the thallium(III)–iodo complex forms and precipitates as a DMSO solvate. In the crystal structure, Tl is surrounded by three iodide ligands in the equatorial plane and two O‐coordinated DMSO molecules in the axial positions, forming a slightly distorted trigonal bipyramid. The complex lies on a twofold rotation axis, making the DMSO molecules and two of the I atoms crystallographically equivalent. 相似文献
90.
1,3-Dipolar Addition of 2-Benzonitrilio-2-propanid to 7-Methylthieno[2,3-c]pyridine 1,1-Dioxide and Subsequent Reactions The addition of dipole 2 , generated photochemically from 2,2-dimethyl-3-phenyl-2H-azirine ( 1 ), to 7-methylthieno[2,3-c]pyridine 1,1-dioxide yields the pyrroline derivative 4 as a major product and regioisomer 5 in low yield. Compound 4 can be transformed into the pyrrolidine derivative 11 by ring opening, loss of SO2 and hydrogenation. Bromopyrroline derivative 14 gives either by dehydrohalogenation compound 18 or, by substitution, nitrile 17 or ethoxy derivative 19 . Substitution of 14 and ring opening yields methoxypyrrole derivative 20 , which gives access to the unstable hydroxypyrrole and hydroxypyrrolidine derivative 28 resp. 30 . The vinylsulfone 18 is the starting material for addition-ring-cleavage reactions. Oxidation of pyrroline derivative 4 gives epoxy-substituted N-oxide 39 and di-N-oxide 40 ; and oxidative transformation of pyrrolidine derivative 11 yields the (hydroxymethyl)pyridylpyrrolidine derivative 45 . 相似文献