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1.
The development of the poly(3‐hydroxybutyrate) (PHB) morphology in the presence of already existent poly(vinylidene fluoride) (PVDF) spherulites was studied by two‐stage solidification with two separate crystallization temperatures. PVDF formed irregular dendrites at lower temperatures and regular, banded spherulites at elevated temperatures. The transition temperature of the spherulitic morphology from dendrites to regular, banded spherulites increased with increasing PVDF content. A remarkable amount of PHB was included in the PVDF dendrites, whereas PHB was rejected into the remaining melt from the banded spherulites. When PVDF crystallized as banded spherulites, PHB could consequently crystallize only around them, if at all. In contrast, PHB crystallized with a common growth front, starting from a defined site in the interfibrillar regions of volume‐filling PVDF dendrites. It formed by itself dendritic spherulites that included a large number of PVDF spherulites. For blends with a PHB content of more than 80 wt %, for which the PVDF dendrites were not volume‐filling, PHB first formed regular spherulites. Their growth started from outside the PVDF dendrites but could later interpenetrate them, and this made their own morphology dendritic. These PHB spherulites melted stepwise because the lamellae inside the PVDF dendrites melted at a lower temperature than those from outside. This reflected the regularity of the two fractions of the lamellae because that of those inside the dendrites of PVDF was controlled by the intraspherulitic order of PVDF, whereas that from outside was only controlled by the temperature and the melt composition. The described morphologies developed without mutual nucleating efficiency of the components. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 873–882, 2003 相似文献
2.
Hans-Rudolf Buser Michael Oehme Walter Vetter Bernd Luckas 《Fresenius' Journal of Analytical Chemistry》1993,347(12):502-512
Summary Conventional electron ionization (EI) mass spectrometry (MS) and MS/MS techniques were applied to the analysis of two abundant octa and nonachlorobornanes isolated from seals of the Baltic sea and originating from technical toxaphene. The exact sterical structures of the two compounds were previously determined using nuclear magnetic resonance (NMR) spectroscopy by two independent research groups. The MS and MS/MS data generated in this study allowed partial structure elucidation of these polychlorobornanes, in particular revealing the distribution of the Cl substituents between the six-membered carbon ring, the bridge and the bridgehead in the parent bornane structure. Fragmentation of the six-membered carbon ring and the bridge by retro-Diels-Alder (RDA) and related mechanisms was discovered by studying specific parent/daughter ion transitions. The detailed fragmentation pathways formulated may be applicable to the structure elucidation of other toxaphene congeners and the monitoring of strategic transitions is highly selective for the detection of these compounds in technical toxaphene and in environmental samples. 相似文献
3.
The reactions of bis(trimethylstannyl)ethyne, Me3Sn–C?C–SnMe3 ( 4 ), with trimethylsilyl‐ or dimethylsilyl‐dialkylboryl‐substituted alkenes 1 – 3 afford organometallic‐substituted allenes 5 , 6 and 8 , 9 in high yield. In the case of (E)‐2‐trimethylsilyl‐3‐diethylboryl‐2‐pentene ( 1) , a butadiene derivative 7 could be detected as an intermediate prior to rearrangement into the allene. All reactions were monitored by 29Si and 119Sn NMR, and the products were characterized by an extensive NMR data set (1H, 11B, 13C, 29Si, 119Sn NMR). Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
4.
The intramolecular Friedel-Crafts cyclisation of ω-arylalkanoic acids, which is in the benzene series a valuable synthetic route to bicyclic ketones with medium-sized and large rings, has been investigated with ω-(1-naphthyl)alkanoyl chlorides. The lower members, including naphthyl-caproic acid, close the ring at position 2 to form IV. The higher homologous acids show a preference for annellation at 7, making available a new type of heteronuclear naphthalene cyclic ketones (VII). During cyclisation of ω-(1-naphthyl) decanoic acid, the 1,4 ring closure competes with the 1,7 type.
Steric hindrance of resonance as a consequence of “medium ring torsion” was studied in different classes of naphthocyclenones. 相似文献
5.
Bernd G. Müller 《Journal of fluorine chemistry》1982,20(3):291-299
Single crystals of CaPdF4 (purple) and CdPdF4 (dark blue) have been obtained by heating CaF2 (CdF2) with PdF2 at 820°C (900°C) for ca. 20–30 d in sealed Pd (Pt) tubes. CaPdF4 crystallizes tetragonal (KBrF4-Type) with a = 5.521, c = 10.570 Å (space group I4/mcm ? D184h, No. 140) Z = 4, 283 unique reflexions, R = 0.083; Rw = 0.079, CdPdF4 cubic (CaF2-variant) with a = 5.403 Å (space group Pa3 ? T6h, No. 205) Z = 4, 165 unique reflexions, R = 0.047, Rw = 0.032. The high pressure modification of PdF2, obtained by heating PdF2 in closed Pt-tubes under a pressure of ≈ 60 kbar and ‘HgPdF4’, both black, a = 5.327 Å and a = 5.43 Å are isotypic. CaPdF4 is diamagnetic, CdPdF4 and HPPdF2 are antiferromegnetic. 相似文献
6.
Thomas Pontani Doz. Dr. Bernd M. Rode 《Monatshefte für Chemie / Chemical Monthly》1977,108(5):1153-1162
The solvating properties of formamide, N-methylformamide, dimethylformamide, N-ethylformamide and diethylformamide have been investigated by means of vapour pressure and conductivity measurements. For the salts and ions, resp. average solvation numbers have been calculated from vapour pressure data and limiting ionic conductances. The solvation numbers are used for a discussion of the influence of N-substituents on the solvating properties of the amides.
Mit 2 Abbildungen 相似文献
Mit 2 Abbildungen 相似文献
7.
[reaction: see text] A sequential solid-phase peptide synthesis was developed using both photolabile linker and protecting groups. The chromatic sequential lability between a tert-butyl ketone-derived linker (sensitive to irradiation at 305 nm) and a nitroveratryloxycarbonyl (NVOC) group (sensitive at 360 nm) was exploited to prepare Leu-Enkephalin in a 55% overall yield. This new strategy allows the preparation of peptides in essentially neutral medium, by avoiding the use of common deprotection reagents such as trifluoroacetic acid or piperidine. 相似文献
8.
Alpha-hydroxy ketones are versatile intermediates for the synthesis of complex molecular architectures and subunits of a variety of natural products. Different approaches towards the synthesis of this important functional group combination have been elaborated. The present article summarises our research on the field of RuO4-catalysed oxidations of alkenes that resulted in the development of the first RuO4-catalysed ketohydroxylation of olefins. Mechanistic investigations of both dihydroxylation and ketohydroxylation led to the discovery of the first regioselective catalytic mono oxidation of vic-diols, which was applied in a two-step sequence of asymmetric dihydroxylation and regioselective mono oxidation to furnish enantiopure alpha-hydroxy ketones with both predictable regioselectivity and absolute configuration. 相似文献
9.
10.
Bernd G. Müller 《无机化学与普通化学杂志》1982,491(1):245-252
New Fluoropalladates(II) Single crystal investigations on \documentclass{article}\pagestyle{empty}\begin{document}$ \begin{array}{*{20}c} {[6][4]} \\ {{\rm CsPdPdF}_{\rm 5} } \\ \end{array} $\end{document} (orange brown) demonstrate the close structural relationship to the CsAgFeF6 – and CsNiNiF6-type, respectively. One half of the Pd2+ ions is surrounded octahedrally, whereas the other half, because of the “absence” of one F?, is coordinated planar quadratically. CsPd2F5 crystallizes orthorhombic (Imma – D, No. 74; Z = 4) with a = 6.533, b = 7.862, c = 10.79 Å (four circle diffractometer data). From Guinier data are isotypic CsMgPdF5 (yellow, a = 6.603(2), b = 7.415(2), c = 10.548(3) Å), CsZnPdF5 (beige, a = 6.576(1), b = 7,483(2), c = 10.645(2) Å), CsNiPdF5 (yellow, a = 6.499(1), b = 7.504(2), c = 10.575(3) Å) and CsCoPdF5 (brown, a = 6.527(1), b = 7.553(1), c = 10.659(2) Å). Besides of CsPd2F5 there exist compounds of the composition Me3PdF5 on the alkali-rich side of the system MeF/PdF2. Single crystal investigations for Rb3PdF3 (yellow, P4/mbm–D, No. 127; Z = 2) led to a = 7.467, c = 6.497 Å (four circle diffractometer data). Isotypic are (single crystal data) Cs3PdF5 (yellow, a = 7.848, c = 6.688 Å) and Rb2CsPdF5 (yellow, ordered distribution of the alkali ions, a = 7.575, c = 6.445 Å). 相似文献