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61.
A set of eighteen imidazol(in)e derivative drugs of various pharmacological activity were analysed under different high-performance liquid chromatographic (HPLC) conditions. Capacity factors were determined employing methanol-buffer eluents at seven volume ratios and at pH 10.9, 7.0 and 2.9. The use of an alkaline buffer was possible owing to the application of poly(butadiene)-coated alumina (PBCA) as the stationary phase. Two systems employing octadecylsilica (ODS) columns were applied, one operated at pH 7.0 and the other at pH 2.9. Capacity factors of the test solute drugs were determined in 21 chromatographic systems. All the data were subjected to chemometric analysis despite the fact that, except for the PBCA systems, only a limited range of linearity of the logarithm of capacity factor versus volume fraction of methanol in mobile phase was observed. The matrix of 21 x 18 capacity factors was statistically analysed by the principal component method. The first two principal components accounted for 80% of the variance in the capacity factors studied. The principal component object scores clearly separated the agents into groups in accordance with their pharmacological classification. It was concluded that diverse retention data can provide more information relevant to the bioactivity of solutes than just a one-dimensional hydrophobicity scale. 相似文献
62.
New Macrolides and Some Sesquiterpenoid Derivatives Occurring in Galbanum Absolute Analytical investigations of a Galbanum absolute have revealed for the first time the presence of four macrolides 1 – 4 derived from the corresponding hydroxylated C13–C16 fatty acids by lactonization of a secondary alcoholic group with the carboxylic group. The musky odor strengthens with increasing number of members in the macrocycle, whereas the woody note is predominant in the smaller rings. Isolation, identification and synthesis of the new naturally occurring substances are described. Shyobunol ( 24 ) epishyobunol ( 25 ) as well as their acetates 26 and 27 were identified - together with 10-epijunenyl acetate ( 28 ) - in the same substrate, thus indicating 25 and 26 to be natural products. The corresponding known and already naturally occurring ketones 23 and 24 are trace components in the investigated material derived from the so-called Galbanum oleo-gum-resin. 相似文献
63.
J. M. Pacheco F. Alasia H. E. Roman R. A. Broglia 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1996,37(3):277-280
A first-principles investigation of the photoabsorption cross section of the specially stable cluster Li12C60 is carried out, including the icosahedral symmetry of the cluster and treating the ions via ab initio pseudopotentials. The role of the coating metal is assessed by computing the same quantity for the fullerene “seed”. It is found that the main absorption features are determined by the carbon molecule, both at low and high excitation energies, in spite of a reduction of 60% for the ionization threshold of Li12C60 as compared to C60. Nonetheless the lithium coating is responsible for small yet clearly observable effects throughout the spectrum, in particular for a more structured and broad strength distribution at excitation energies below the ionization threshold of C60, and a double peak structure in the Mie resonance at ≈20 eV. 相似文献
64.
Roman Dziembaj 《Journal of solid state chemistry》1978,26(2):167-171
Using the redox mechanism of vanadia catalyst action as a starting point, oxygen binding energy and its measurement have been discussed. Experimental results on the equilibrium oxygen pressure are presented and two types of equilibrium are distinguished: chemisorbed and redox. It has been shown that univariant redox equilibrium is appropriate for characterizing vanadia catalysts. 相似文献
65.
Marián Kucharík František Šimko Vladimír Danielik Miroslav Boča Roman Vasiljev 《Monatshefte für Chemie / Chemical Monthly》2007,138(12):1211-1215
Summary. The phase diagram of the system Na3AlF6–NaVO3 was determined by means of thermal analysis. The system is a simple binary eutectic one. The eutectic point was estimated
at x(NaVO3) = 0.975 and t
eut = 617°C. The XRD patterns of samples after thermal analysis revealed the presence of cryolite and NaVO3 only supporting the above assumption of a simple eutectic binary system. 相似文献
66.
Jaromir Dmytrzyk Andrzej Kotarba Hanna Grabowska Roman Klimkiewicz 《Research on Chemical Intermediates》2004,30(3):337-342
The influence of gas-phase methylation of phenol on the state of the Fe-Si-Cr-K oxide catalyst surface was investigated by thermodesorption of K atoms and ions. Changes in potassium desorption energies, as determined from Arrhenius-like plots, varied from 3.07 eV to 1.21 eV for the atoms and from 2.59 eV to 2.89 eV for ion desorption from the active and deactivated samples, respectively. The results were discussed in terms of transformation of the catalyst surface and formation of β-ferrite. 相似文献
67.
Lucjan Chmielarz Piotr Kustrowski Marek Michalik Barbara Dudek Magdalena Czajka Roman Dziembaj 《Reaction Kinetics and Catalysis Letters》2007,91(2):369-378
Natural phlogophite, pre-treated with acids and intercalated with alumina pillars, was used as catalytic support. Transition
metals (Fe, Cu) were deposited on the surface of the modified clay materials by an ion-exchange method. The obtained samples
were characterized with respect to structure (XRD), texture (BET), composition (EPMA) and chemical nature of the deposited
transition metals species (UV-vis-DRS). The phlogophite based materials have been found to be active and selective catalysts
of the DeNOx process. The Fe-containing samples were catalytically active at lower temperatures than the clays modified with
copper. A competitive ammonia oxidation by oxygen decreased the effectiveness of the DeNOx process in the high temperature
range. 相似文献
68.
The occurrence of a series of new constituents which can be considered as Diels-Alder adducts of methyl vinyl ketone and ocimene (→1–4), myrcene (→ 9 , 10 ) or β-far-nesene ( → 11 , 12 ), respectively, was reported. Furthermore, the structures of four isomeric cyclohexene derivatives could be established as adducts 21–24 of (E, Z)- and (E, E)-1,3,5-undecatrience and methyl vinyl ketone. Another series of constituents having the norbornane skeleton represents adducts 25–32 , and 33–40 of methyl cyclopentadiene and 1-octen-3-one or methyl vinyl ketone, respectively. In accordance with Alder's endo-rule the endo-isomers are preponderant in the natural as well as in the synthetic mixtures. Most of these constituents could also be identified in a lavender absolute as well as in a freshly prepared hexane extract of lavender flowers (Lavandula officinalis CHAIX ). 相似文献
69.
E. Roman M. Sánchez-Avedillo J. L. de Segovia 《Applied Physics A: Materials Science & Processing》1984,35(1):35-40
In the present work, results of the interaction of O2 with polycrystalline titanium using AES, and ELS techniques, are presented. Changes in the shapes of Ti(LMV) and Ti(LMM) transitions and in the Ti(LM)O(V)/Ti(LMV) and Ti(LMV) Ti(LMM) amplitude ratios as well as a shift of the 34 eV loss peak [Ti(3p level], are studied as function of the oxygen exposure.At O2 pressures equal or less than 10–6 Pa and exposure up to 2000 L(O2) (weak oxidation), the Ti(LM)O(V)/Ti(LMV) and Ti(LMV)/Ti(LMM) ratios show three clearly distinct regions: (i) up to 20L there is a chemisorbed phase with the Ti(LMV)/Ti(LMM) ratio remaining constant and a fast linear increase in the Ti(LM)O(V)/Ti(LMM) ratio. (ii) At exposures higher than 20L the oxidation begins being characterized by a linear variation of the Ti(LM)O(V)/Ti(LMV) and Ti(LMV)/Ti(LMV) ratios, with positive and negative slopes, respectively. (iii) At 125L there is a change in both slopes but no stable value is achieved, despite the O(KLL)/Ti(LMM) ratio remains constant. Hence, it can be concluded that TiO is the final oxide obtained after that treatment, from features like the shape of the transitions and a maximum shift of 3eV of the Ti(3p) level, complemented with ESD experiments.On the other hand, experiments at pressures higher than 10–4Pa with or without the surfaces at 900K (strong oxidation) indicate that the most likely final oxide is TiO2.Work presented to the IXIVC-VICSS. Madrid (1983) 相似文献
70.
Roman Mazurkiewicz 《Monatshefte für Chemie / Chemical Monthly》1989,120(11):973-980
Summary N-Acylanthranilamides react with dibromotriphenylphosphorane in the presence of triethylamine as HBr captor to give 4-imino-4H-3,1-benzoxazines in good yields. If the reaction is carried out without acid acceptor, N-acetylanthranilamides yield 2-methyl-4-quinazolones, whereas N-benzoylanthranilamides give 2-phenyl-4-imino-4H-3,1-benzoxazines. It has also been found that 2-methyl-4-imino-4H-3,1-benzoxazines rearrange under the influence of HCl or HBr into the respective 2-methyl-4-quinazolones; 2-phenyl-4-imino-4H-3,1-benzoxazines, however, do not undergo such a rearrangement.
Synthese und Umlagerung von 4-Imino-4H-3,1-benzoxazinen
Zusammenfassung Die Umsetzung von N-Acyl-anthranilsäure-amiden mit Triphenyldibromphosphoran in Gegenwart von Triethylamin als HBr-Akzeptor führt mit guten Ausbeuten zu 4-Imino-4H-3,1-benzoxazinen. Wird die Reaktion ohne säurebindendes Mittel durchgeführt, dann entstehen aus N-Acetyl-anthranilsäure-amiden 2-Methylchinazolone-4, jedoch erhält man aus N-Benzoylanthranilsäure-amiden 2-Phenyl-4-imino-4H-3,1-benzoxazine. 2-Methyl-4-imino-4H-3,1-benzoxazine erleiden unter dem Einfluß von HBr oder HCl eine Umlagerung in entsprechende 2-Methylchinazolone-4, während 2-Phenyl-4-imino-4H-3,1-benzoxazine zu einer solchen Umlagerung nicht befähigt sind.相似文献