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排序方式: 共有66条查询结果,搜索用时 15 毫秒
1.
2.
V. I. Minkin I. E. Mikhailov G. A. Dushenko O. E. Kompan A. Zschunke 《Russian Chemical Bulletin》1998,47(5):884-894
The kinetics and mechanism of circumambulatory rearrangements of N-centered (NCS) and S-centered (SPh, SC3Ph3, SC(OEt)=S) groups in corresponding derivatives of 1,2,3-triphenylcyclopropene and cycloheptatriene were studied by dynamic1H and13C NMR spectroscopy. Migrations of the isothiocyanate group occur by the dissociation-recombination mechanism with intermediate formation of a tight ionic pair. Migrations of the phenylthio group around the perimeter of cyclopropene and cycloheptatriene rings occur by the 1,2-shift mechanism. It was found that rearrangements of theO-ethyl dithiocarbonate group inS-(1,2,3-triphenylcyclopropen-3-yl)-O-ethyl dithiocarbonate occur by the 3,3-sigmatropic shift mechanism. The molecular and crystal structure ofO-ethylS-(1,2,3-triphenylcyclopropen-3-yl) dithiocarbonate was studied by X-ray analysis. 相似文献
3.
Oliver Tietze Birgit Schiefner Burkhard Ziemer A. Zschunke 《Analytical and bioanalytical chemistry》1997,357(5):477-481
The reaction of ethylenediamine with an equivalent mixture of diversely substituted 3-acyltetramic acids leads to Z/Z, Z/E,
E/Z and E/E isomers. The E/Z isomerisation is slow in the NMR time scale of the 1H and 13C chemical shifts; therefore at room temperature and in deuterochloroform all isomers of the new synthesized asymmetric compounds
N,N′-ethylene-(1-ethyl-5,5-dimethyl-1′,5′,5′-trimethyl-3,3′-acetyltetramic acid) a, N,N′-ethylene-(5,5-dimethyl-1′,5′,5′-trimethyl-3,3′-acetyltetramic
acid) b and, N,N′-ethylene-(1,5,5-trimethyl-1′,5′,5′-trimethyl-3-acetyl-3′-formyl-tetramic acid) c could be found in the corresponding
spectra. To assign the 13C NMR signals we used two-dimensional 13C-1H one-bond (HMQC) and 13C-1H multibond (HMBC) correlated spectroscopy and the empirical rule that CO signals involved in hydrogen bonds are shifted to
a lower field. The relative stability of isomers depending on substitution pattern could be estimated from the composition
of the equilibria. b crystallizes as Z/Z isomer from ethanolic solution. The X-ray structural analysis of b has shown two
CH-O hydrogen bonds.
Received: 31 May 1996 / Revised: 26 June 1996 / Accepted: 1 July 1996 相似文献
4.
A. Zschunke H. Meyer I. Heidlas B. Messbauer B. Walther H.-D. Schdler B. Thomas 《无机化学与普通化学杂志》1983,504(9):117-127
31P and 195Pt N.M.R. Investigations on Diplatinum (I) Complexes of the Type [Pt2(μ-SPR2)2L2] (L = PR3, PhP(OPh)2, P(OPh)3, CNR) 31P-, 195Pt-chemical shifts and 195Pt–31P- resp. 31P–31P-coupling constants of a series of doubly bridged diplatinum(I) complexes are reported. 31P-coordination chemical shifts of the terminal ligands of complexes of type [Pt2(μ-SPR2)2(P′R3′)2] and some of the various coupling constants are strongly influenced by the π-acceptor strength of these ligands. J(195Pt–195Pt) is found to change the sign among the series of complexes investigated. Thermal singlett triplet exitation giving rise to the paramagnetism of these complexes observed by preliminary EPR-measurements and confirmed by EHT-calculations is deduced from the large values of 2J(P–P′) and 3J(P′P′) as well as the unusually high temperature dependence of some coupling constants and other NMR features. The chemical stability of the doubly bridged core, the coordination shifts of the bridging phosphorus atoms and EHT-calculations suggest a view of aromaticity of the [Pt2(μ-SPR2)2](M–M) unit of these complexes. 相似文献
5.
Contributions to the Chemistry of Transition Metal Diolefin Complexes. II. Characterization of Phosphine-stabilized Iron Diolefin Complexes Bis(butadiene)triphenylphosphine iron and Bis(isoprene)triphenylphosphine iron are characterized by protolytic reactions, mass spectrometrical fragmentations and NMR-spectra. A structure for this compounds is proposed on the basis of the NMR spectra. 相似文献
6.
7.
1H-NMR-Spektroskopische Untersuchungen zur Konformation von Cyclohexandicarbonsäure-(1,2)-anhydriden
H. Werner A. Zschunke G. Mann E. Kleinpeter 《Magnetic resonance in chemistry : MRC》1975,7(10):478-484
1H NMR chemical shifts of 18 methyl substituted cyclohexane-1,2-dicarboxylic anhydrides were determined. In compounds with asymmetric substitution vicinal coupling constants were measured. In the series of trans-anhydrides it can be deduced from the NMR data, that the 6-membered ring has a chair-like conformation. Additionally, in the series of the cis-anhydrides a twisted chair conformation is favoured for the most part. 相似文献
8.
The Correlation of Tolman's Cone Angles with 1J of Phosphonium Fluorosulfonates A 1H-n.m.r. study of three series of phosphonium salts [HPR3?nHn]X, and [HPPh2R1?nHn]X and (R = aliphatic substituent and H, X = SO3 F) gives a good relationship between increasing values of 1J versus decreasing size of substituted phosphines. A method to obtain Tolman's cone angle is described. 相似文献
9.
10.
Isomerization at the Complexation of 3-Acetyltetramic Acid: Structure and Magnetic Properties of the CuII- and NiII-Complex of 2,7-Bis (1′, 5′, 5′ -trimethylpyrrolidin-2′,4′ -dion-3′ -yl)-3,6-diazaocta-2,6-dien 2,7-Bis(1′, 5′, 5′ -trimethylpyrrolidin-2′, 4′ -dion-3′ -yl)-3,6-diazaoctadien formes CuII and NiII complexes with different constitutions (because of the Z/E isomerization). Results of X-ray analysis of N,N′ -ethylenbis(1′, 5′, 5′ -trimethylpyrrolidin-2′, 4′ -dion-3′ -acetiminato)nickel(II) 1 respectively -copper(II) 2 shows, that the complexing agent in 1 occurs in the E-form, whereas the ligand of the CuII complex forms the Z-form. Magnetic susceptibility and shift effects of the 13C-NMR signals point to a weak paramagnetism of the NiII complex. ESR-spectra are obtained from 2 only. Furthermore, the CuII complex reduces the relaxation times T1 and T2 of 1H and 17O nuclei spins from water. From the temperature dependence of the shortening of the relaxation times an activation energy is calculated which describes the reorientation of the copper complex in the “water matrix”. 相似文献