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61.
James E. Douglass Elba Michelena Ali Ataei Darin L. Dotson Herng-Hsiang Lo 《Journal of heterocyclic chemistry》1992,29(5):1361-1363
The quinaldyl ketone, 4-phenyl-3-(quinolin-2-yl)-butan-2-one was prepared by two methods: (a) benzylation of 1-(1H-quinolin-2-ylidene)propan-2-one in the presence of sodium hydride in dimethylformamide and (b) by the benzylative demethoxycarbonylation of methyl 2-(1H-quinolin-2-ylidene)-3-oxobutanoate in the presence of lithium bromide in hexamethylphosphoramide at 135°. In the absence of acid, the compound exists exclusively in the tautomeric form, 4-phenyl-3-(1H-quinolin-2-ylidene)butan-2-one. 相似文献
62.
John K. Gallos Pygmalion S. Lianis Nestor A. Rodios 《Journal of heterocyclic chemistry》1994,31(2):481-487
A series of substituted furazano[3,4-b]quinoxaline 1-oxides have been prepared by oxidation of the respective 2,3-bis(hydroxyimino)-1,2,3,4-tetrahydroquinoxalines with nitric acid and their structure was confirmed by means of their nmr spectra. A very rapid equilibrium occurs between their two isomeric N-oxide forms via the dinitroso equivalent, and the influence of the 6(7)-substituents on the equilibrium is discussed. These compounds were easily deoxygenated by triphenylphosphine in quantitative yields to the corresponding furazans. The electron impact mass spectra of both of the above series of compounds have also been recorded and their fragmentation pattern is discussed. 相似文献
63.
Gregory R. Lumpkin Miguel Pruneda Katherine L. Smith Karl R. Whittle Nestor J. Zaluzec 《Journal of solid state chemistry》2007,180(4):1512-1518
The radiation tolerance of synthetic pyrochlore and defect fluorite compounds has been studied using ion irradiation. We show that the results can be quantified in terms of the critical temperature for amorphization, structural parameters, classical Pauling electronegativity difference, and disorder energies. Our results demonstrate that radiation tolerance is correlated with a change in the structure from pyrochlore to defect fluorite, a smaller unit cell dimension, and lower cation-anion disorder energy. Radiation tolerance is promoted by an increase in the Pauling cation-anion electronegativity difference or, in other words, an increase in the ionicity of the chemical bonds. A further analysis of the data indicates that, of the two possible cation sites in ideal pyrochlore, the smaller B-site cation appears to play the major role in bonding. This result is supported by ab initio calculations of the structure and bonding, showing a correlation between the Mulliken overlap populations of the B-site cation and the critical temperature. 相似文献
64.
The synthesis of the title Compounds is described. Their mass spectra upon electron impact are given and the main fragmentation pathways are described. 相似文献
65.
Castro K Sarmiento A Maguregui M Martínez-Arkarazo I Etxebarria N Angulo M Barrutia MU González-Cembellín JM Madariaga JM 《Analytical and bioanalytical chemistry》2008,392(4):755-763
A complete study of several English polychromed alabaster sculptures is presented. The support, pigment, and binders were
characterised by combining μEDXRF, μRaman, and FTIR spectroscopies. Among the pigments, minium, vermilion, lead white, carbon
black, red iron oxide, and a degraded green copper pigment were determined, together with gold leaf. The presence of the rare
mineral moolooite (copper oxalate) was also found as a degradation product in the green areas, where weddellite (calcium oxalate
dihydrate) was also determined. These facts, together with degradation of the green copper pigment, suggest microbiological
degradation of the original materials. Remains of glue and a varnish were also determined by FTIR spectroscopy and principal-components
analysis (PCA) of the spectra. Finally, PCA analysis was carried out to confirm whether the pieces came from the same quarry. 相似文献
66.
A new and efficient conjugate addition of trialkylphosphites to 3-ω-bromoacetylcoumarin 1 catalysed by p-toluenesulfonic acid (TsOH) has been studied. Under the same conditions, an enolphosphate gave the corresponding esters of 3-acetyl-4-phosphono-2-oxochromans in high yields. The use of TsOH in the reaction of 3-acetyl-, 3-benzoyl-, and 3-ethoxycarbonyl coumarins led mainly to 1,4-addition products—the corresponding 3-acyl-4-dialkylphosphono-2-oxochromans—in very good yields. 相似文献
67.
68.
69.
Nestor Grehant 《Fresenius' Journal of Analytical Chemistry》1908,47(6-7):434-435
Ohne Zusammenfassung 相似文献
70.
Esquena J Nestor J Vílchez A Aramaki K Solans C 《Langmuir : the ACS journal of surfaces and colloids》2012,28(33):12334-12340
A novel and simple single-step method for the preparation of meso/macroporous silica materials is described, which consists in templating in highly concentrated emulsions with a cubic liquid crystal in the continuous phase. Tetraethyl orthosilicate (TEOS) was solubilized in the aqueous continuous phase of highly concentrated emulsions stabilized by C(12)(EO)(8) and a PEO-PPO-PEO block copolymer nonionic surfactant, with a cubic liquid crystalline phase of the Fd3m type. The resulting silica materials were characterized by small-angle X-ray scattering, nitrogen sorption and transmission electron microscopy. The results showed that a dual pore size distribution was obtained, consisting of mesopores in the nanometer range and macropores between 1 and 5 μm. These dual meso/macroporous silicas with bimodal pore size distribution can possess specific surface areas higher than 400 m(2)/g. 相似文献