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61.
Israel Agranat 《Journal of mass spectrometry : JMS》1973,7(7):907-909
The mass spectral fragmentations of 1,2-diphenyl- and 1,2-di (phenyl-d5)-4,5-benzotriapentafulvalene-3,6-quinone indicate the preferred elimination of two CHO groups with the formation of triafulvalene radical cations. 相似文献
62.
A simple, compact, easy-to-implement microprocessor ratemeter for kinetic determinations based on initial rate, fixed time, and variable time is presented. The hardware and software are such that the ratemeter can be used with almost any transducer or instrument to monitor reactions in a wide variety of chemical systems. The performance of the ratemeter is demonstrated by its application to the determination of phosphorus by stoppedflow spectrometry, glucose by amperometry, and alkaline phosphatase activity in control sera by visible spectrophotometry. 相似文献
63.
A number of substituted butatriene-bis-tricarbonyliron complexes have been studied by 13C and 1H n.m.r. spectroscopy. Long range coupling values, J(CCCH), have confirmed chemical shift results that methyl and phenyl groups assume opposite orientations at the coordinated double bonds with the methyl group preferentially trans to carbon and the phenyl group preferentially trans to iron. 相似文献
64.
The knapsack problem, maximize Σmi = 1cixi when Σmi = 1aixi?b for integers xi?0, can be solved by the classical step-off algorithm. The algorithm develops a series of feasible solutions with ever-increasing objective values. We make a change in the problem so that the step-off algorithm produces a series of solutions of not necessarily increasing objective values. A point is reached when no better solutions can be found and the calculation is stopped. 相似文献
65.
Bidentate intermolecular Si...N interactions were utilized to form new hypervalent complexes of trifluoro-phenylethynyl-silane with 2,2'-bipyridine and with 1,10-phenanthroline. X-ray structures obtained for these complexes display a somewhat distorted octahedral geometry about the silicon atom. Binding constants ranging from 170 to 1600 M(-1) at 25 degrees C in CDCl3 were measured for the formation of these complexes, suggesting that such hypervalent complexes of silicon could be used as new motifs in supramolecular chemistry. 相似文献
66.
Fluorescent optical imaging of tumors deep within tissue depends on specific binding of antibodies to the tumors' surface markers. These fluorescent antibodies propagating in the vicinity of the tumor can be attached to and (or) diffused away from it. We illustrate application of a new tool, based on the random-walk theory in turbid media, for extracting the pharmacokinetics of these fluorescent antibodies by data deconvolution, excluding the effect of upper turbid tissue layers. 相似文献
67.
Israel Schleicher 《电子设计技术》2003,10(10):82
图1所示电路的输出电流在1.2~1.5V的输入电压范围内几乎是恒定的,并对晶体管的增益变化不敏感.晶体管Q1和Q2组成一个非稳态触发器.R1和C确定Q2的导通时间.在Q2导通期间,Q1截止,Q1的基极电压和电感器L中的电流逐渐升高.当Q1的基极电压达到大约0.6V时,Q1导通,而Q2截止.这种转换在电感器L中引起"逆转"动作.电感器两端的电压极性相反,存储在电感器中的能量以下降的脉冲电流形式传送给LED.在逆转期间,LED两端的电压几乎是恒定的. 相似文献
68.
Reactions of carbonate radical anion with amino-carboxylate complexes of manganese(II) and iron(III)
Amir Mizrahi Eric Maimon Haim Cohen Israel Zilbermann 《Journal of Coordination Chemistry》2018,71(11-13):1749-1760
AbstractThe reaction kinetics of eight amino-carboxylate complexes of Fe(III) and Mn(II) with carbonate radical anion were studied using the pulse radiolysis method and UV-vis spectroscopy. Difference spectra revealed the formation of Fe(IV) and Mn(III) after reaction with CO3??. Spectral measurements revealed the first step to be the coordination of carbonate to the metal center. All of these led to the conclusion that the role of coordinated carbonate is essential to the electron transfer process by carbonate radical anion. 相似文献
69.
Wulff WD Korthals KA Martínez-Alvarez R Gómez-Gallego M Fernández I Sierra MA 《The Journal of organic chemistry》2005,70(13):5269-5277
By means of deuterium-labeling experiments, we have carried out a systematic ESI-MS study to determine the mechanism of ESI ionization of alkenyl and alkynyl group 6 Fischer carbene complexes. These compounds can be ionized under ESI conditions only in the presence of additives such as hydroquinone (HQ) or tetrathiafulvalene (TTF). Our results demonstrate that in the ESI source an anion-radical is formed after the initial HQ- or TTF-mediated electron transfer to the metallic carbene complex. For alkenyl carbene complexes, this species evolves by extrusion of a hydrogen radical to form an allenylchromium anion that is detected as the [M - H](-) ion in the mass spectrum. The preference for this mechanistic pathway could be rationalized by DFT calculations. In the case of alkynyl carbene complexes, experiments combining deuterated substrate, additive, and solvent demonstrate that the previously proposed allene-anion carbene complex is not formed. Instead, the H transfer from the ethoxy group in the anion radical, followed by extrusion of a hydrogen radical, leads to an allenyl anion that is detected in the ESI-MS as [M - H - CO](-). 相似文献
70.
Prof. Dr. Daniel Solé Francesco Mariani Prof. Dr. M.‐Lluïsa Bennasar Dr. Israel Fernández 《Angewandte Chemie (International ed. in English)》2016,55(22):6467-6470
A palladium‐catalyzed carbene insertion into C(sp3)?H bonds leading to pyrrolidines was developed. The coupling reaction can be catalyzed by both Pd0 and PdII, is regioselective, and shows a broad functional group tolerance. This reaction is the first example of palladium‐catalyzed C(sp3)?C(sp3) bond assembly starting from diazocarbonyl compounds. DFT calculations revealed that this direct C(sp3)?H bond functionalization reaction involves an unprecedented concerted metalation–deprotonation step. 相似文献