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171.
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Łapczuk-Krygier Agnieszka Jaśkowska Jolanta Jasiński Radomir 《Chemistry of Heterocyclic Compounds》2018,54(12):1172-1174
Chemistry of Heterocyclic Compounds - The molecular mechanism of nitrous acid elimination from 5-nitro-3-phenyl-4,5-dihydroisoxazole systems has been explored using DFT computational study. It was... 相似文献
174.
A reaction of Grignard reagents with an optically pure N-sulfinylimine derived from methyl 2-formylbenzoate yields enantioenriched isoindolinones and tert-butyl sulfoxides. The products are formed by the addition of the nucleophile to N-sulfinylimine followed by cyclization to form N-tert-butylsulfinylisoindolinone, which readily undergoes substitution with a second equivalent of Grignard reagent. The reaction can be carried out in dichloromethane at room temperature or at elevated temperatures without any loss of stereoselectivity. The use of nucleophiles other than Grignard reagents has also been investigated. 相似文献
175.
Agnieszka Tomaszewska Grzegorz Moskal Damian Migas Marta Mikuśkiewicz Tomasz Maciąg 《Journal of Thermal Analysis and Calorimetry》2018,134(1):157-164
The γ–γ′ Co-based superalloys are newly developed class of refractory alloys which may replace commercial Ni-based superalloys owing to their favorable properties at high temperature. In case of new Co-based superalloys, the heat treatment aims to obtain microstructure composed of appropriate volume fraction of small cuboidal γ′-Co3(Al,W) precipitates within the γ-Co matrix. However, due to a high tendency to interdendritic segregations of alloying elements, the alloys based on Co–Al–W system should be normally homogenized before further steps of heat treatment (solutionizing and aging). In this study, thermal analysis was applied for determination of temperature range for primary heat treatment of the Co–9Al–9W (at.%). The differential thermal analysis (DTA) measurements were carried out on the thermal analyzer NETZSCH STA 449 F3 Jupiter. On the base of obtained results, respectively, solvus of γ′ phase and solidus temperatures were determined, as well as the thermal range of Co3W (DO19) phase precipitation. As a consequence, the heat treatment without homogenizing (only solution and aging) was proposed as a most suitable way to obtain beneficial microstructure. 相似文献
176.
M. W. Wieczorek G. D. Bujacz E. Galas J. Zjawiony A. Wojciechowska 《Journal of chemical crystallography》1989,19(5):883-892
The crystal structure of the title compound has been determined with three-dimensional MoK X-ray diffraction data. The space group and unit-cell parameters are:P21/c,a=8.610(3) Å,b=13.516(5) Å,c=16.818(5) Å,=94.95(3)° andV=1950.0(7) Å3. The structure was solved by direct methods, and refined by full-matrix least-squares techniques toR=0.0608 andR
w=0.0648. The compound is a derivative of the popular-adrenolytic propranolol, and in the propanol part of the side chain shows the typicalgauche conformation. 相似文献
177.
Avigo D Godoi AF Janissek PR Makarovska Y Krata A Potgieter-Vermaak S Alfoldy B Van Grieken R Godoi RH 《Analytical and bioanalytical chemistry》2008,391(4):1459-1468
The particulate matter indoors and outdoors of the classrooms at two schools in Curitiba, Brazil, was characterised in order
to assess the indoor air quality. Information concerning the bulk composition was provided by energy-dispersive x-ray fluorescence
(EDXRF). From the calculated indoor/outdoor ratios and the enrichment factors it was observed that S-, Cl- and Zn-rich particles
are of concern in the indoor environment. In the present research, the chemical compositions of individual particles were
quantitatively elucidated, including low-Z components like C, N and O, as well as higher-Z elements, using automated electron
probe microanalysis low Z EPMA. Samples were further analysed for chemical and morphological aspects, determining the particle
size distribution and classifying them according to elemental composition associations. Five classes were identified based
on major elemental concentrations: aluminosilicate, soot, organic, calcium carbonate and iron-rich particles. The majority
of the respirable particulate matter found inside of the classroom was composed of soot, biogenic and aluminosilicate particles.
In view of the chemical composition and size distribution of the aerosol particles, local deposition efficiencies in the human
respiratory system were calculated revealing the deposition of soot at alveolar level. The results showed that on average
42% of coarse particles are deposited at the extrathoracic level, whereas 24% are deposited at the pulmonary region. The fine
fraction showed a deposition rate of approximately 18% for both deposition levels. 相似文献
178.
Lesaw Siero Katarzyna Kie‐Kononowicz Janina Karolak‐Wojciechowska 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(2):m79-m82
The two title mononuclear compounds are four‐coordinate bis[N‐(5‐oxo‐4,4‐diphenyl‐4,5‐dihydro‐1H‐imidazolidin‐2‐ylidene)glycinato]copper(II) dimethylformamide disolvate, [Cu(C17H14N3O3)2]·2C3H7NO, (I), and five‐coordinate aquabis[N‐(5‐oxo‐4,4‐diphenyl‐4,5‐dihydro‐1H‐imidazolidin‐2‐ylidene)glycinato]copper(II) dimethylformamide disolvate, [Cu(C17H14N3O3)2(H2O)]·2C3H7NO, (II). In (I), the CuII ion lies on an inversion centre with one‐half of the complex molecule in the asymmetric unit, while in (II) there are two independent ligand molecules in the asymmetric unit, with the CuII ion and coordinated water molecule located on a general position. In both crystal structures, the complex molecules assemble in ribbons via N—H...O hydrogen‐bond networks. 相似文献
179.
Anna Doga Katarzyna Baranowska Agnieszka Pladzyk Katarzyna Majcher 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(7):m259-m263
The complexes [2‐(1H‐imidazol‐4‐yl‐κN3)ethylamine‐κN]bis(tri‐tert‐butoxysilanethiolato‐κS)cobalt(II), [Co(C12H27O3SSi)2(C5H9N3)], and [2‐(1H‐imidazol‐4‐yl‐κN3)ethylamine‐κN]bis(tri‐tert‐butoxysilanethiolato‐κS)zinc(II), [Zn(C12H27O3SSi)2(C5H9N3)], are isomorphous. The central ZnII/CoII ions are surrounded by two S atoms from the tri‐tert‐butoxysilanethiolate ligand and by two N atoms from the chelating histamine ligand in a distorted tetrahedral geometry, with two intramolecular N—H...O hydrogen‐bonding interactions between the histamine NH2 groups and tert‐butoxy O atoms. Molecules of the complexes are joined into dimers via two intermolecular bifurcated N—H...(S,O) hydrogen bonds. The ZnII atom in [(1H‐imidazol‐4‐yl‐κN3)methanol]bis(tri‐tert‐butoxysilanethiolato‐κ2O,S)zinc(II), [Zn(C12H27O3SSi)2(C4H6N2O)], is five‐coordinated by two O and two S atoms from the O,S‐chelating silanethiolate ligand and by one N atom from (1H‐imidazol‐4‐yl)methanol; the hydroxy group forms an intramolecular hydrogen bond with sulfur. Molecules of this complex pack as zigzag chains linked by N—H...O hydrogen bonds. These structures provide reference details for cysteine‐ and histidine‐ligated metal centers in proteins. 相似文献
180.
Krzymiński K Roshal AD Niziołek A 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,70(2):394-402
The long-wavelength absorption of eight 9-(phenoxycarbonyl)-acridines and the 10-H-9-(phenoxycarbonyl)-acridinium and 10-methyl-9-(phenoxycarbonyl)-acridinium cations derived from them, substituted with an alkyl or trifluoroalkyl group at the benzene ring, occurs above 300 nm as the superposition of four bands. Three of these bands occupy comparable positions (expressed in nm) in all the compounds; the fourth one, however, changes position, appearing in neutral molecules as a long-wavelength shoulder below 400 nm, but in cations as an almost separate band above 400 nm. The weak fluorescence resulting from excitation within the long-wavelength absorption band is red-shifted relative to absorption, such that Stokes shifts are similar for both neutral molecules and cations. Stokes shifts tend to increase with the orientational polarisability of a medium. Computations predict that long-wavelength electronic transitions are accompanied by structural changes in molecules. They also indicate that such transitions are followed by roughly uniform electron density changes in whole molecules accompanied by small changes in their dipole moments, which accounts for the weak absorption in the long-wavelength region. The predicted radiative and non-radiative deactivation rate constants suggest the occurrence of efficient spin-orbital coupling in the molecules investigated, which is the cause of the relatively low fluorescence quantum yields. Apart from the cognitive significance of these investigations, the results demonstrate that absorption of radiation by 10-methyl-9-(phenoxycarbonyl)-acridinium cations above 400 nm may influence their chemiluminescence output. 相似文献