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1.
Giancarlo Beggiato Giuseppe Casalbore Giancarlo Marconi Claudio Baraldi 《Monatshefte für Chemie / Chemical Monthly》1985,116(3):311-321
The kinetics of charge-transfer interaction betweenp-toluidine and iodine in methylene chloride was investigated in depth. Thethermal process of formation of theinner complex was found to proceed to an equilibrium. Thephotochemical process follows a different reaction coordinate, going through the formation of an exciplex between the excitedouter complex and the amine ground state. In both cases the same ionic complex (Am
2I+I
3
–
, whereAm stands forp-toluidine) was detected as the final product.
Kinetische Untersuchung der Charge-Transfer-Komplexe zwischenp-Toluidin und Jod
Zusammenfassung Die Kinetik der Charge-Transfer-Wechselwirkung zwischenp-Toluidin und Jod in Methylenchlorid wurde ausführlich untersucht. Derthermische Prozeß, der zur Bildung desinner-Komplexes führt, geht bis zu einem Gleichgewicht. Derphotochemische Prozeß folgt einer unterschiedlichen Reaktionskoordinate und verläuft über die Bildung eines Exziplexes zwischen dem angeregtenouter-Komplex und dem Amin im Grundzustand. In beiden Fällen wurde derselbe ionische Komplex (Am 2I+I 3 – , wobeiAm fürp-Toluidin steht) als Endprodukt festgestellt.相似文献
2.
Summary The separation of some purines by thin-layer chromatography, utilizing precoated plates with Silicagel R as stationary phase and the following mobile phases: i-butanol: methylethylketone: ammonium hydroxide 25%: water (40252015) and n-propanol: ammonium hydroxide 25%: water (80155) is reported.Visualisation of the spots has been achieved by spraying with aqueous 1% uranyl acetate and irradiating with UV both at 254 and 366 nm. The visual detection of a spot was 0.01 g. 相似文献
3.
A. G. Ryabenko V. E. Muradyan S. E. Esipov N. I. Cherepanova 《Russian Chemical Bulletin》2003,52(7):1516-1521
The transformation of the mass spectra of the laser-desorbed C60 and C70 samples with a successive increase in the laser power, resulting in an increase in the degree of excitation of C60 (C70) and in the number of the particles in the laser plume, was studied. Unusual metastable clusters (C60 + C2) and (C70 + C2) are formed even at a minimum laser power and begin to dissociate after 0.5 s following a short (3 ns) laser pulse. An increase in the laser power results in the appearance of peaks of metastable clusters C62 (C72) with the statistically normal lifetime without a delay of dissociation. A further increase in the laser power produces metastable clusters C60k–2n
and C70k–2n
(k = 2, 3) formed without a lag from the dimers and trimers of C60 (C70) by the ejection of a number of C2 required for the stabilization of the C2 molecules. The peak of C70 appears simultaneously with the appearance of the (C60)2–2n
peaks upon the laser desorption of pure C60. These findings provide evidence for the growth of the excited fullerene clusters by coalescence and subsequent stabilization due to the ejection of a small fragment rather than by the implantation of C2 into the fullerene framework. This mechanism of cluster growth should be taken into consideration in modeling fullerene formation in an electric arc reactor, because the clusters formed under these conditions have a substantial excess internal energy. 相似文献
4.
Zhang Fuji Sven J. Cyvin Björg N. Cyvin 《Monatshefte für Chemie / Chemical Monthly》1990,121(5):421-432
Summary A type of graphs derived from a cycle and associated with primitive coronoids are referred to as crowns. The characteristic polynomials and matching polynomials of crowns are studied. These notions are used to calculate the sextet polynomial for primitive coronoids. Patterns of aromatic sextets are treated in some detail.
Crowns und aromatische Sextette in einfachen coronoiden Kohlenwasserstoffen
Zusammenfassung Eine Graphentype, die von einem Cyclus abgeleitet ist und mit einfachen Coronoiden verknüpft ist, wird als Crown bezeichnet. Die charakteristischen Polynome und die matching Polynome der Crowns werden untersucht. In diesem Rahmen werden die Sextett-Polynome für einfache Coronoide berechnet. Die Muster der aromatischen Sextette werden im Detail behandelt.相似文献
5.
Summary The Hirshfeld population analysis scheme which carves the molecular density into atomic density contributions is tested. This method does not require a reference to basis sets or their respective locations, but is based on a different physical and mathematical footing. The advantage of this method is that, when the molecular deformation density converges to the true solution, the computed net charges will necessarily converge. This method also allows a straightforward definition for local moments. About 36 molecules have been used to compute the conventional Mulliken and Löwdin population analyses with STO3G, 6311G** and Dunning-Hay split valence basis sets. These results have been compared to the estimates provided by the Hirshfeld model. The charges found in the Hirshfeld method are smaller than those from the other methods. 相似文献
6.
Sven J. Cyvin 《Monatshefte für Chemie / Chemical Monthly》1989,120(3):243-252
Summary Primitive coronoids of hexagonal symmetry (D
6h
orC
6h
) are referred to as waffles. Some theorems about unbranched catacondensed benzenoids are presented and used to derive a general combinatorial formula for the number of Kekulé structures (K) for waffles. The symmetry-adapted method of fragmentation is employed. SeveralK formulas for special classes of waffles are also reported.
Die Anzahl von Kekulé-Strukturen für einige aromatische Coronoid-Kohlenwasserstoffe: Waffel-Strukturen
Zusammenfassung Einfache Coronoide von hexagonaler Symmetrie (D 6h oderC 6 h) werden als Waffel bezeichnet. Einige Theoreme bezüglich unverzweigter catakondensierter Benzenoide werden angegeben und zur Ableitung einer generellen Formel für die Anzahl von Kekulé-Strukturen (K) für Waffel benutzt. Es wird die symmetrie-adaptierte Methode zur Fragmentierung angewendet. Außerdem werden einigeK-Formeln für spezielle Klassen von Waffeln angegeben.相似文献
7.
Summary A previous paper established the principle of hairdressing showing that polyethylene shish-kebab fibres can be reversibly transformed by appropriate preparation conditions between three morphologies, smooth fibres; fibres with closely spaced lamellar overgrowths; fibres with widely spaced lamellar overgrowths, where the spacing is sensitively affected by storage temperature (3). In the present paper this hairdressing work is extended to include the molten state. Three classes of morphology analogous to the three obtained from solution (although with certain minor differences) can be obtained by melting shish-kebabs at constant length, followed by quenching or isothermal crystallization. These melt-hairdressed fibres can be transformed back into shish-kebabs of typical solvent hairdressed appearance by the previously established procedures for solvent hairdressing. Thus all these works, following on from the trend established by Pennings (4), serve to highlight the fact thatall shish-kebabs acquire their external morphology at temperatures which are beneath those of the core formation during final cooling or storage and thatall external forms associated with a given core are interconvertible. On the molecular level these features highlight the intrinsically hairy nature of the core fibre as formed.With 5 figures 相似文献
8.
Terry A. Miller 《Plasma Chemistry and Plasma Processing》1981,1(1):3-18
Diagnostic techniques for low-pressure, cold plasmas have mostly been limited to emission and mass spectrometry. Herein, the techniques of gas-phase electron paramagnetic resonance and laser-induced fluorescence spectroscopy are briefly reviewed. Particular attention is paid to their attributes which make them good candidates for plasma diagnostic tools. It is found that gas-phase electron paramagnetic resonance can be used to determine and monitor the absolute concentration of a number of important plasma species, e.g., free radicals and atoms. Laser-induced fluorescence can also monitor, with even more sensitivity, but perhaps not so well absolutely, the concentrations of many plasma species, e.g., free radicals, metastable excited states, and molecular ions. 相似文献
9.
P. A. Pavlov 《Chemistry of Heterocyclic Compounds》2001,37(9):1175-1176
10.
The 1-[1,8-bis(dimethylamino)-4-naphthyl[ethyl carbocation generated from the corresponding alcohol in benzene in the presence of Al2O3 undergoes elimination according to theE1 mechanism to give previously unknown 1,8-bis(dimethylami no)-4-vinyl naphthalene in a good yield. This compound was also synthesized from 1,8-bis(dimethylamino)-4-formylnaphthalene by the Wittig reaction. Polymerization of the vinylic derivative obtained was studied.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2297–2300, September, 1996. 相似文献
11.
El-Sayed A. M. Badawey Samia M. Rida Farid S. G. Soliman Thomas Kappe 《Monatshefte für Chemie / Chemical Monthly》1989,120(12):1159-1164
Summary The syntheses of 3-chloro derivatives of 2-alkyl-pyrimido[1,6-a]benzimidazol-1(2H)-ones2a, b as well as of 4,4-dichloro and 4,4-dibromo derivatives of 2-alkylpyrimido[1,6-a]benzimidazole-1,3(2H,4H)-diones3 a, b and4 are reported. Methods for converting some of the chloro compounds to azido (5, 6), amino (8), morpholino (9 a,10,11), piperidino (9 b), cyano (12), and methoxy (13) derivatives of the adopted tricyclic system are also described.
Kondensierte Ringsysteme des Benzimidazols, 6. Mitt.: Organische Azide in der Heterocyclen-Synthese, 10. Mitt.: Synthese von substituierten Pyrimido[1,6-a]benzimidazolen als mögliche antimikrobielle Wirkstoffe
Zusammenfassung Die Synthese von 3-Chlor-2-alkyl-pyrimido[1,6-a]benzimidazol-1(2H)-onen (2 a, b) und von 4,4-Dichlor- und 4,4-dibrom-pyrimido[1,6-a]benzimidazol-1,3(2H,4H)-dionen (3 a, b, 4) wird beschrieben. Diese Verbindungen lassen sich zu den entsprechenden Azido- (5, 6), Amino- (8), Morpholino- (9 a, 10, 11), Piperidino- (9 b), Cyano- (12) und Methoxy- (13) Derivaten umwandeln.相似文献
12.
S. Felder-Casagrande H. G. Wiedemann A. Reller 《Journal of Thermal Analysis and Calorimetry》1997,49(2):971-978
The calcination of limestone is one of the oldest technical processes and it is still of actual interest. Very early calcitic mortars from Turkey have been investigated and compared with materials of other early civilisations i.e. with Egyptian mortars containing gypsum as well as medieval dolomite-based mortars from alpine regions. Contemporary calcination procedures, in particular the cement production, range among the most important global industrial processes causing non neglectable environmental problems. Sustainable, solar energy assisted calcination technologies and the conversion of product CO2 into useful commodities are discussed.The authors like to thank Prof. K. von Salis Perch-Nielson, Institute of Geology, ETH Zürich, for assistance in sedimentological investigations. 相似文献
13.
Adamantanol was obtained by the ozonization of adamantane, at -78 ° C, adsorbed on silica gel. Ozone does not decompose on silica gel in the absence of a substrate.Ozonization of adamantane on silica gel is accompanied by chemiluntinescence in the IR region. The chemiluminescence quenching is of first-order with the effective rate constantk'. In the range from 0.4 to 5 mmol, k' depends linearly on the amount of adamantane adsorbed on the silica gel. The activation energy Ea = 9.97±1.89 kcal mol–1 and the pre-exponential factorA = (2.76±0.52) - 106 were calculated from the temperature dependence ofk'.Translated from Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 375–378, February, 1996. 相似文献
14.
The problem of the possibility of applying ap-correlation analysis by the three sigmas' system to carbanion reactions with electrophilic reagents was considered. In particular the alkylation as well as Wittig and Homer olefination reactions were discussed. It was shown that the condition for the application of correlation analysis to such reactions is the constancy of the Brönsted's parameter connected with steric and reorganization factors of the substrates and solvents. Perfect correlations were observed when this condition was met.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 634–639, March, 1996. 相似文献
15.
The effect of melt annealing duration at 260 °C-high above melting temperature on the crystallization of nylon-6 with various molecular weights (between 5 800 and 255 500) using dilatometric and calorimetric (DSC) techniques has been studied. The samples were laboratory synthesized, purified and characterized by GPC. It was found that the crystallization behavior of nylon-6 depends strongly on the melt annealing duration as well as on the molecular weight. This effect is explained by the gradual destruction of the crystallization centers during annealing of the melt. The experimental data support the well known memory effect and the recently observed accumulative memory effect on the same polymer 相似文献
16.
Heinz Berner Hermann Vyplel Gerhard Schulz Helmut Schneider 《Monatshefte für Chemie / Chemical Monthly》1986,117(8-9):1073-1080
The reaction of pleuromutilin-22-0-tosylat(2) withEtZnI afforded a mixture of the 12-epimeric compounds2 and3. A reversible retro-en-reaction of the homoallylic system is discussed as a possible mechanistic pathway. The structure assignment is based on1H- and13C-NMR spectroscopic data.
Für Verbindungen dieser Substanzklasse, die auf ihre antibakterielle Aktivität geprüft werden, ist erfahrungsgemäß eine basisch substituierte Acylgruppierung in Position 14 erforderlich4. Heterocyclische Acylgruppierungen erwiesen sich dabei als besonders wirkungsvoll. 相似文献
17.
18.
C. Zylka 《Theoretical chemistry accounts》1985,68(5):363-377
In this paper, we consider regions of attainability in certain state spaces as a function of the initial state under a well-defined and physically relevant class of processes. These processes are the continuous and chaos-enhancing processes (in the sense of Ruch and Uhlmann). It turns out that these sets have complicated geometrical structures: They are polyhedra which are generally non-convex. The proof — a rather geometrical one — is given. A theorem of Hardy, Littlewood, and Polya and properties of bistochastic matrices are used crucially. 相似文献
19.
In this paper we describe a system for interactive picture analysis useful for extraction of various types of physical information from both real- and Fourier-space images. The possibility of hardware and software operations are illustrated, with examples of applications such as analysis of light scattering patterns from phase separated systems, semicrystalline polymer films with significant supermolecular morphology and from less regular polymer systems with a pronounced speckle effect. The analysis concentrates on both spatial and time dependent scattering processes and measurements of intensity correlation of scattered light. Although the present examples of application are limited to light scattering patterns of polymer systems, the technique of interactive picture analysis is useful for quantitative extraction of information from real-and Fourierspace images of arbitrary structure. 相似文献
20.
K. -H. Frömming V. Wedelich W. Mehnert 《Journal of inclusion phenomena and macrocyclic chemistry》1987,5(5):625-629
- and -Cyclodextrin (CD) and heptakis-2,6-di-O-methyl--cyclodextrin (DIMEB) form soluble inclusion compounds with mefenorex (MEF); with -CD a partial inclusion occurs. No solid inclusion compound could be obtained with the four CDs. -, -CD and DIMEB, but not -CD, enhance the nitrosation rate of MEF if the nitrosation assay procedure (NAP test) is applied. During this reaction with - and -CD, solid inclusion compounds of the CDs and nitrosomefenorex (NMEF) precipitate.Part of the Ph.D. thesis of V. Wedelich, Freie Universität Berlin, 1985. 相似文献