Search results for "Molecule"
showing 10 items of 5162 documents
Thermal rearrangements of 1,2-dialkoxybenzenes by flash vacuum pyrolysis
1995
Flash vacuum pyrolysis of 1,2-dialkoxybenzenes 1a-c leads to the liberation of alkanes from the interacting side chains. A rearrangement of the skeleton yields the o-hydroxy carbonyl compounds 2 and 4. The generation of phenol 3 can be rationalized by a decarbonylation. The latter reaction is the sole process which can be observed for the bicyclic starting compound 9.
Studies in organic mass spectrometry. IV. Electron impact induced fragmentation of 2-substituted 3-(5-isoxazolyl)-4(3H)-quinazolinones of pharmaceuti…
1984
The fragmentation under electron impact of thirteen 2-substituted-3-(5-isoxazolyl)-4(3H)-quinazolinones has been investigated with the aid of metastable ion detection and high resolution measurements. Molecular ions are always abundant and the main primary fragmentation route involves acetonitrile elimination through isoxazole ring opening. The other common processes, particularly those leading to the abundant [R-C8H4N2]+ ion (b or b'), as well as those due to the nature of the 2-substituent are reported and discussed.
Schrittweise synthesen und eigenschaften einiger cyclopentamerer aus methylenverbrückten (5-alkyl-2-hydroxy-1,3-phenylen)-bausteinen
1981
Three cyclopentamers (2a–c) and a chainlike pentanuclear oligomer (3a) were prepared by stepwise syntheses. The molecules of the cyclic compounds with 20 links contain o,o′-methylene bridged 2-hydroxy-5-methyl-1,3-phenylene or 2-hydroxy-5-tert-butyl-1,3-phenylene units in a strictly defined manner. The properties of the cyclic pentamer 2a and the chainlike pentanuclear oligomer 3a were compared. They differ by their solubilities, melting points, IR and 1H NMR spectra (pseudorotation) and fragmentation behaviour shown by their mass spectra. The pseudorotation of the cyclic compounds were quantitatively studied.
DFT Study on the Complex Reaction Networks in the Conversion of Ethylene to Ethylidyne on Flat and Stepped Pd
2009
Adsorption and conversion of ethylene to ethylidyne on flat (111) and stepped Pd surfaces have been studied with the aim to unravel the complex chemistry of small organic molecules on Pd. These pro...
Topical Anti-Inflammatory Lignans from Haplophyllum hispanicum Haplophyllum hispanicum
1996
The present paper reports the results of the methanol extract of Haplophyllum hispanicum Spach on single or repeated local 12-O-tetradecanoylphorbol acetate (TPA) administration and in the oxazolone-induced contact-delayed hypersensitivity mouse ear edemas. Two topical anti-inflammatory aryl naphthalide lignans were isolated from the active fractions of the methanol extract. They were identified by spectroscopic methods, including 13C NMR and heteronuclear multiple bond correlation (HMBC), as diphyllin acetyl apioside and tuberculatin. The former was the most active on acute TPA edema with a ID50 of 0.27 μmol/ear
Unequivocal determination of isomeric products of reaction between 3-methyl-1-phenyl-2-pyrazoline-4,5-dione and aromatic 1,2-diamines
1999
Abstract Regioselectivity of condensation of 3-methyl-1-phenyl-2-pyrazoline-4,5-dione with aromatic 1,2-diamines is dependent on substituent present. Isomeric 3-methyl-1-phenyl-1H-pyrazolo-[3,4-b]-quinoxaline products are distinguished by comparison of their 2D z-gradient selected 1H, 15N HMBC (Heteronuclear Multiple Bond Correlation) spectra. Multiplicity of H5 signal, which is recognizable by the cross-peak for CH3(3)-N4 and H5-N4 interactions, indicates substitution in position 6 or 7. The applied method is expected to be useful for structure determinations in other positional isomers.
Terrylene in p-terphenyl: single-molecule experiments at room temperature
1999
Abstract This paper reports on fluorescence microscopy and spectroscopy of single terrylene molecules embedded in p -terphenyl at room temperature. The basic photophysical parameters of this crystalline host/guest system such as photostability, single-molecule emission rates and the properties of dispersed fluorescence spectra are reported. The stability of the single-molecule signals allowed the direct observation of singlet–triplet quantum jumps at room temperature, by means of which the underlying intersystem crossing rates can be investigated. The results of earlier investigations at liquid-helium temperatures are reviewed briefly where appropriate. The properties of terrylene in p -ter…
Polycondensed nitrogen heterocycles. Part 22. Pyrrolo[3,4-d]-1,2,3-triazines: A new ring system as potential antineoplastic agent
1989
Diazotization of the 3-aminopyrrole-4-carboxamides 6a,b under different conditions directly led to the new ring system pyrrolo[3,4-d]-1,2,3-triazine in excellent yields through an intramolecular coupling reaction. In all the cases it was impossible to isolate the intermediate 3-diazopyrroles.
Defects and Reactivity at Oxide Surfaces: Experimental Aspects of the Interaction of Hydrogen, Co And Co2 with the Nio{001} Surface
1989
This paper summarizes some previous or more recent experimental results on chemical interaction, at moderate temperatures, of H, H2, CO and CO2 with the surfaces of nickel oxide, mainly the NiO {001} surface. These results are in a general agreement with theoretical predictions. Nearly perfect surfaces of maximal valency oxides cannot react with molecules. Dissociation of molecules is often required for chemisorption. Conversely, chemical reaction is usually observed either when molecules are predissociated or the surface has defects with an energy level high enough to enable both dissociation and chemisorption. On a nearly perfect, “in situ” cleaved, NiO {001} surface, partially atomized h…
Investigation of Charge-Transfer Interactions Induced by Encapsulating Fullerene in a Mesoporous Tetrathiafulvalene-Based Metal-Organic Framework
2019
<p>The design of Metal-Organic Frameworks (MOFs) incorporating electroactive guest molecules in the pores has become a subject of great interest in order to install additional electrical functionalities within the framework while maintaining porosity. In this direction, understanding the charge-transfer (CT) process between the framework and the guest molecules is crucial towards the design of new electroactive MOFs. Herein, we present the encapsulation of fullerenes (C<sub>60</sub>) in a mesoporous tetrathiafulvalene(TTF)-based MOF. The CT process between the electron-acceptor C<sub>60 </sub>guest and the electron-donor TTF ligand is studied in detail by means…