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991.
Klok HA Rösler A Götz G Mena-Osteritz E Bäuerle P 《Organic & biomolecular chemistry》2004,2(24):3541-3544
The first example of an oligothiophene-peptide conjugate, which was obtained by solid-phase acylation of a resin-bound silk-inspired oligopeptide sequence with a carboxylic acid functionalized regioregular tetra(3-hexylthiophene) derivative, is reported. 相似文献
992.
[n.n.n]Propellanes and bicyclo[n.n.n]alkanes (1=n=3) in which the bridgeheads and bridges are composed of different Group 14 elements will not be ideal homologues of the all-carbon propellanes and bicycloalkanes. We used quantum-chemical calculations to conclude which of these could possibly be stable at ambient temperature. Structures, strain, and dimerization energies of [n.n.n]propellanes and bicyclo[n.n.n]alkanes with C-based tethers and with Si, Ge, or Sn at the bridgehead positions were calculated. The aptitude to add water was probed in selected cases. Comparisons were made with the analogous all-C propellanes and bicycloalkanes. All heavy 1,(n+2)-dimetallabicyclo[n.n.n]alkanes should be thermally stable and suitable synthetic targets, even though the moisture sensitivity of 1,3-dimetallabicyclo[1.1.1]pentanes increases as Group 14 is descended. For 1,(n+2)-dimetalla[n.n.n]propellanes, the incompatibility between the tether and M--M bond lengths impacts strongly on structure and stability. At ambient temperature 1,3-disila[1.1.1]propellanes should oligomerize instantly upon formation, whereas 1,3-digerma- and 1,3-distanna[1.1.1]propellanes should be less prone to oligomerize and possibly isolable. The 1,4-dimetalla[2.2.2]propellanes with M=Si-Sn have biradical ground states and can presumably only be observed under inert conditions at cryogenic temperatures. Finally, we predict that 1,5-disila[3.3.3]propellane will be persistent at ambient temperature, but 1,5-distanna[3.3.3]propellane should rapidly oligomerize. 相似文献
993.
Walter M. F. Fabian Gert Kollenz Yunus Akcamur Tevfik Riza Kök Makbule Teczan Mehmet Akkurt Wolfgang Hiller 《Monatshefte für Chemie / Chemical Monthly》1992,123(3):265-275
Summary 4-Benzoyl-5-phenylfuran-2,3-dione (1) and the urethanes2 combine under loss of carbon monoxide yielding the open chain dibenzoylacetic acid derivatives3 and4. 3a, b only can be cyclized to the oxazinone5. The keto-enole tautomerism3 4 is further investigated with aid of semiempirical quantum chemical calculations, based upon the molecular geometry of3a, deduced from an X-ray study.
Frau Univ. Prof. Dr. Helga Wittmann mit den besten Wünschen zum 70. Geburtstag gewidmet. 相似文献
994.
Layered organic derivatives of crystalline zirconium phosphate were synthesized and investigated for their intercalation behaviours. Derivatized zirconium phosphates having hydroxy groups take up different polar molecules such as alcohols, amines etc. by increasing the interlayer distance determined by X-ray diffraction method. The intercalation processes on these materials can be considered as heterogenous phase acid-base reactions. 相似文献
995.
Zusammenfassung Es wird über Strom-Spannungskurven in Phenylphosphoroxydichlorid berichtet, welche mit verschiedenen Elektrodenkombinationen erhalten wurden. Die bei der Polarographie leitsalzfreier Phenylphosphoroxydichloridlösungen beobachteten Erscheinungen werden auf Migrationsströme zurückgeführt.Mit 3 Abbildungen3. Mitt.:H. Dehn, V. Gutmann undG. Schöber, Mh. Chem.94, 312 (1963). 相似文献
996.
The synthesis of cephalotaxine ring analogues 10 was achieved by two successive intramolecular palladium-catalyzed reactions of 12 via 11, namely an allylic amination and a Heck reaction. The substrates 12 were obtained by alkylation of primary amines 13 with tosylates 14. 相似文献
997.
Cu(II), Co(II), Ni(II), and Zn(II) metal complexes with new heterocyclic Schiff base derived from 1-amino-5-benzoyl-4-phenyl-1H-pyrimidine-2-one and 3-methoxysalicylaldehyde have been synthesized and characterized on the basis of elemental analyses, electronic, IR, and 1H NMR spectra, and also by aid of molar conductivity measurements, magnetic moment measurements, and thermogravimetric analyses. It has been found that the Schiff base behaves as a neutral bidentate (NO) and tridentate (ONO) ligand forming chelates with 1 : 2 (metal : ligand) stoichiometry. Octahedral configuration is suggested for metal complexes. The conductivity data for the Ni(II) complexes are consistent with those expected for a 1 : 2 electrolyte. 相似文献
998.
999.
An evaluation of the non-boiling evaporation technique for the preconcentration of Pb, Cd, Cu, Zn at the pg g?1 level in water samples is presented. Various improvements were made to allow efficient control of contamination problems at these extremely low concentrations. They include the choice of FEP Teflon for the evaporation containers and the use of sophisticated cleaning, ageing and pre-conditionning procedures. Detailed calibration graphs were obtained down to the sub-pg g?1 level by processing ultra-low concentration standards. This technique was then applied to the determination of these four metals in snow samples collected in Greenland and Antarctica. 相似文献
1000.
On-line coupled liquid chromatography-gas chromatography 总被引:1,自引:0,他引:1
On-line coupled liquid chromatography–gas chromatography (LC–GC) is a powerful technique that combines the best features of LC and GC and is ideal for the analysis of complex samples. This review describes the unique features of on-line coupled LC–GC. The different interfaces and evaporation techniques are presented, along with their advantages and disadvantages. Guidelines are given for selecting a suitable LC–GC technique and representative applications are noted. 相似文献