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41.
[formula: see text] The synthesis of all four diastereomers of bis(propionates), 3,5-dialkoxy-2,4-dimethylalkanals, by non-aldol aldol chemistry is described. The epoxy alcohols (3, 4) were converted into the mesylates (9, 11) which were cleanly rearranged to the desired 3,5-bis(oxygenated)-2,4-dimethylalkanals (10, 12) in high yield. The epoxy mesylates (13, 16) gave the desired products (14, 17) in good yield on treatment with TMSOTf and a hindered base. 相似文献
42.
Chi YS Jung YH Choi IS Kim YG 《Langmuir : the ACS journal of surfaces and colloids》2005,21(10):4669-4673
In this paper, we report surface-initiated d(A-T) polymerization by Taq DNA polymerase as a method for constructing DNA-tethered surfaces using an enzyme. The enzymatic polymerization was conducted successfully via two steps: tethering of oligo d(A-T)s onto the surface presenting carboxylic acids by amide coupling and surface-initiated polymerization using Taq DNA polymerase. In this enzymatic polymerization process, the design and construction of carboxylic acid-presenting surfaces were found to be an important factor: DNA growth did not occur on the gold surface coated only with the self-assembled monolayer (SAM) of 16-mercaptohexadecanoic acid (MHDA), but effectively proceeded on the surfaces presenting mixed SAMs of MHDA and 1-pentadecanethiol. The coupling of oligo d(A-T)s and the subsequent DNA polymerization reaction were characterized by polarized infrared external reflectance spectroscopy, ellipsometry, X-ray photoelectron spectroscopy, and atomic force microscopy. 相似文献
43.
Self-assembling structures of long-chain phenyl glucoside influenced by the introduction of double bonds 总被引:1,自引:0,他引:1
Jung JH John G Yoshida K Shimizu T 《Journal of the American Chemical Society》2002,124(36):10674-10675
Four long-chain phenyl glucoside amphiphiles possessing a saturated or unsaturated long alkyl chain group as the self-assembling unit of a highly organized molecular architecture were synthesized. Their self-assembling properties were investigated by EF-TEM, SEM, CD, FT-IR, and XRD. Compound 2 possessing one double bond in the lipophilic portion showed twisted helical fibers, which formed a bilayered structure with a 3.59 nm period, while compound 3 showed the helical ribbons and left-handed nanotubular structures with 150-200 nm inner diameters and ca. 20 nm of wall. Very interestingly, compound 4 possessing three double bonds showed a nanotubular structure with ca. 70 nm of inner diameter through a helical ribbon, which formed a loose bilayered structure with 4.62 nm. These results indicate that self-assembling properties strongly depend on the number of cis double bonds. 相似文献
44.
Theoretical and experimental study of the adsorption on radioactive gases on continuous flow columns
A bimolecular reaction model was used to describe the adsorption process in continuous flow columns filled with solid adsorbents. The analytical solution of the model for low gas concentrations and a cascade-type numerical method for higher gas concentrations were developed. An air flow apparatus using activated carbon as adsorbent and methyl-iodide labelled with125I as adsorbate was constructed for measuring breakthrough- and accumulation curves. 相似文献
45.
Zusammenfassung Das Nicotellin enthält wahrscheinlich nicht, wie die meisten anderen Tabakalkaloide, 2 N-Atome in der Molekel, sondern hat die Formel C15H11N3. Es werden gewichtige Gründe dafür beigebracht, es als 3,2;6,3-Terpyridyl (I) aufzufassen. Diese Hypothese wird durch Synthese des damit isomeren 3,2;4,3-Terpyridyls (V) und Vergleich der Infrarotspektren der beiden Terpyridyle mit denen von 4 bekannten Bipyridylen gestützt. Betrachtungen über eine mögliche Synthese des Nicotellins in der Pflanze führen zu Versuchen, diese Synthese in vitro nachzuahmen; diese Versuche geben aber eine andere Verbindung, wahrscheinlich das 1,5-Di--pyridyl-pentadien-(1,4)-on-(3).Herrn Prof. Dr.L. Ebert zum 60. Geburtstage in aufrichtiger Verehrung gewidment. 相似文献
46.
Configurationally and conformationally homogeneous cyclicN-aryl sulfimides. II.13C-and1H NMR spectra
Peter K. Claus Werner Rieder Friedrich W. Vierhapper 《Monatshefte für Chemie / Chemical Monthly》1978,109(3):631-650
The configuration and (in case of mobile ring systems) the preferred conformation in a series of thiane- and ofcis-andtrans-1-thiadecalin-1-N-4-chlorophenyl imides were assigned by means of13C- and1H nmr spectroscopy.1H nmr criteria known to be valid for determination of the stereochemistry of cyclic sulfoxides may be applied (with limitations) to cyclicN-aryl sulfimides, if both isomers (S–N bond equatorial and axial, respectively) are known. The assignments are easier, and unambiguous for single isomers, by comparison of13C nmr chemical shifts of ring carbon atoms of sulfimides and sulfides. The influence of equatorially and axially oriented sulfimide groups on the chemical shifts of neighbouring protons, and on the carbon atoms of the heterocyclic rings are discussed in detail.
Konfigurativ und konformationell einheitliche cyclische N-Aryl-sulfimide. II.13C- und1H-NMR-Spektroskopie
Zusammenfassung Die Konfiguration und (bei beweglichen Ringsystemen) die bevorzugte Konformation einer Reihe von Thian- und voncis- undtrans-1-Thiadekalin-1-N-4-chlorophenylimiden wurde durch13C- und1H-NMR-Spektroskopie bestimmt. Bekannte1H-NMR-Kriterien zur Festlegung der Stereochemie cyclischer Sulfoxide sind (mit Einschränkungen) auch bei cyclischenN-Arylsulfimiden anwendbar, wenn beide Isomere (S–N-Bindung äquatorial bzw. axial) bekannt sind. Leichter, und auch bei Vorliegen von nur einem Isomeren eindeutig, gelingt die Zuordnung durch Vergleich der13C-NMR-Verschiebungen der Ringkohlenstoffatome von Sulfimiden und Sulfiden. Die Einflüsse äquatorial oder axial orientierter Sulfimidgruppen auf die chemischen Verschiebungen benachbarter Wasserstoffe und der Kohlenstoffe des Heterorings werden diskutiert.相似文献
47.
Grein F 《The Journal of chemical physics》2005,122(12):124504
For Ne(n)-AlO (n=2, 4, 6, 8, 10) and Ar(n)-AlO clusters (n=2, 4, 6, 8), the perpendicular (relative to AlO) component of the g tensor was calculated by second-order perturbation theory, using multireference configuration-interaction wave functions. The rare-gas (Rg) atoms were placed axially and/or off axially (one or two rings of four Rg atoms each), and the distance of the Rg atoms from the Al and O atoms, or from the AlO axis, was varied from 4 to 12 bohrs. Rg atoms placed axially mostly increase g(perpendicular), whereas off-axially placed ones lower it below the gas-phase value of AlO. The largest deviations from g(perpendicular) of isolated AlO occur at Ne-Al,O distances of 5-6 bohrs, and Ar-Al,O distances of 6-9 bohrs, with maximal lowerings of about 1600 ppm for Ne and about 2200 ppm (estimated) for Ar in the case of two axial and eight off-axial Rg atoms. Electron spin resonance studies by Knight and Weltner found large matrix effects for AlO, with downshifts of g(perpendicular) observed to be about 450 and 1150 ppm in Ne and Ar matrices, respectively. 相似文献
48.
G. Miksch E. Liebermann Friedrich Kohler 《Monatshefte für Chemie / Chemical Monthly》1969,100(5):1574-1582
Zusammenfassung Totaldampfdrucke des Systems 1,2-Dichloräthan + Cyclohexan wurden bei 13°, 20° und 32° C über den gesamten Konzentrationsbereich gemessen. Für Cyclohexan-reiche Mischungen des Systems wurde ferner die Schmelzkurve bestimmt. Aus diesen Meßgrößen wurde die zusätzliche freie Mischungsenthalpie G
E des Systems für verschiedene Temperaturen berechnet. Bei 20°C beträgt G
E für die äquimolare Mischung 773 J/mol. Ein Vergleich mit Literaturangaben über die Mischungswärme (H=1611 J/mol für äquimolare Mischung bei 20°C) ergibt, daß die zusätzliche Mischungsentropie S
E des Systems stark positiv ist. Eine Interpretation der Ergebnisse wird in einer anderen Arbeit gegeben, wo auch Ergebnisse an anderen Dihalogenäthan + Kohlenwassersoff-Systemen berücksichtigt werden.
Mit 5 Abbildungen 相似文献
Free enthalpy of mixing for the system 1,2-dichloroethne-cyclohexane
Total vapour pressures of the system 1,2-dichloroethane + cyclohexane were measured at 13°, 20° and 32°C over the total concentration interval. For mixtures rich in cyclohexane the
Mit 5 Abbildungen 相似文献
49.
Christian C. Van de Sande Syed Zahoor Ahmad Friedrich Borchers Karsten Levsen 《Journal of mass spectrometry : JMS》1978,13(11):666-670
Gaseous protonated aziridine ions are produced at the threshold from β-phenoxyethylamine molecular ions. The evidence for this is collisional activation spectra, using various precursors (including labelled analogues) under electron impact and field ionization conditions. Partial conversion to the acyclic \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CH}_{\rm 3} {\rm CH = }\mathop {\rm N}\limits^ + {\rm H}_{\rm 2} $\end{document} isomer occurs at higher electron energies and is rationalized by means of a potential energy surface constructed from energetic data. 相似文献
50.
Friedrich Boberg Maria Ruhr Karl-Heinz Garburg Alfons Garming 《Journal of heterocyclic chemistry》1986,23(3):759-766
Dihydro-1,2-oxazines 8 and 12-oxazines 12 are formed by the reaction of the nitronic acids of the adducts of α-nitroolefins and β-dicarbonyl compounds ( 6 ) by two ways: A ) The nitronic acids 6 are heated in a boiling solution of urea in ethanol or methanol. B ) The nitronic acids 6 are reduced with an aqueous solution of ammoniachloride and sodium sulfide. 1H-nmr and 13C-nmr investigations prove the constitutions. The mechanism is discussed. 相似文献