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31.
Abachi S Baringer P Bylsma BG DeBonte R Koltick D Loeffler FJ Low EH McIlwain RL Miller DH Ng CR Rangan LK Shibata EI Derrick M Gan KK Kooijman P Loos JS Musgrave B Price LE Repond J Sugano K Weiss JM Wood DE Blockus D Brabson B Brom J Jung C Ogren H Rust DR Akerlof C Chapman J Errede D Kesten P Meyer DI Nitz D Seidl AA Thun R Willutzky M Cork B 《Physical review letters》1986,57(16):1990-1993
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The preparation of η-C3H5V(CO)5 from allyl chloride and sodium hexacarbonylvanadate (–I) is reported. Composition, IR and NMR spectra are in accordance with a π-bonded C3H5-moiety; the preparation has been extended to give complexes with substituted allyl groups. Furthermore (1-3-η-2-butenyl)pentacarbonylvanadium can be obtained by the addition of butadiene to HV (CO)6. 相似文献
37.
In a weakly acidic solution, the addition of HBr to 1-phenylprop-1-yne produces predominantly the anti-Markovnikov product. In this paper, we consider five possible explanations for this behavior and conclude that the concerted addition is occurring on the acetylenic pi bond orthogonal to the extended aromatic pi system. The electronic effect of the distal methyl group and the steric hindrance of the coplanar phenyl ring combine to promote bromide attack at the beta carbon. Attack on this pi bond is insensitive to the electronic effect of meta and para substituents on the ring but is very (sterically) sensitive toward all ortho substituents. 相似文献
38.
Joachim Heidberg Elisabeth Kampshoff Helmut Stein Helmut Weiss Michael Warskulat 《Mikrochimica acta》1988,94(1-6):105-108
Sample/spectrum relationships are investigated using both a low resolution rapid-scanning NIR monochromator and a Fourier transform instrument capable of high resolution and are evaluated in terms of whether or not the resolution of the instrument is sufficient for measuring the natural bandwidths corresponding to the sample. Based on the sample/spectrum relationship a criterion is developed which must be followed in order to apply either derivative spectroscopy or deconvolution to enhance the resolution of overlapped bands without generating spectral artifacts. 相似文献
39.
Liquid crystalline ionomers containing sulfonate groups on the terminal unit of the chain were synthesized by an interfacial condensation reaction of 4,4′-dihydroxy-α,α′-dimethyl benzalazine, the monofunctional dye fast yellow (FY), and a 50/50 mixture of sebacoyl and dodecanedioyl dichlorides. The weight-average molecular weights were estimated from inherent viscosity measurements to be between 6000–11,000 and the sodium sulfonate concentrations ranged from 0–18.4 meq/100 g polymer. Elemental analyses, however, indicated much higher molecular weights, which suggested that there was a distribution of chains with one, two, or no FY endgroups. The polymers were semicrystalline and melted at ca. 140°C to form nematic mesophases that were stable over a temperature range of ca. 80°C. They were thermally stable to about 350°C. The ionomeric nature of the polymers was confirmed by the presence of intermolecular associations in nonpolar solvents, as demonstrated by dilute solution viscosity measurements. 相似文献
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The presence of 19 cardenolides in the extracts from the seeds of Acokanthear oppositifolia (Lam.) CODD could be traced by means of paper chromatography. Thirteen of these cardenolides could be isolated in crystalline form, acovenoside A (= 2) being by far the major component. Of the other 12 crystalline substances, 5 could be identified with known cardenolides: 2′ = acofrioside L, 3 = acolongifloroside H, 14 = acovenoside C, 15 = acolongifloroside K, 16 = ouabain. The substances 1′, 1″, 4, 6, 7, 8 and 13 are very probably new compounds. Four of these were given trivial names and the following structures were proposed: 1″ = oppovenoside, probably 10 ; 4 = oppofrioside ( 5 ); 6 = acotaloside ( 6 ); 13 = opposide, probably 12 , cf. following publication [21]. Furthermore, the structure 8 has been proposed for acolongifloroside H. 相似文献