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61.
Wileńska B Danikiewicz W Bugaj M Kamieńska-Trela K Krówczyńsk A 《European journal of mass spectrometry (Chichester, England)》2011,17(3):237-243
Electron ionization (EI) and positive electrospray ionization (ESI) mass spectra of selected diaryl enaminoketones and enaminothiones have been studied. In the EI mass spectra of both classes of compound, molecular ion peaks are accompanied by the peaks corresponding to the [M-H](+) ions. The formation of these ions can be rationalized by a cyclization reaction resulting in the formation of the respective isoxazolium and isothiazolium cations. Under positive ESI conditions, in the spectra recorded for the enaminoketones peaks corresponding to the [M+H](+), [M+Na](+) and [2M+Na](+) ions appeared, while in the spectra recorded for the enaminothiones, peaks corresponding to the [M-H](+) ions were dominant. These ions are most likely formed by oxidation of the neutral enaminothione molecules on the surface of the positively charged stainless steel capillary in the ESI ion source (anodic oxidation). 相似文献
62.
The oxidation process of 1-methoxy-4-(1-methylethyl)benzene catalysed by N-hydroxyphthalimide (NHPI) or NHPI in combination
with Cu(II), Co(II), Mn(II) and Fe(II) salts was studied. The effects of the amount of catalyst and the temperature were determined.
1-Methyl-1-(4-methoxyphenyl)ethyl hydroperoxide was obtained in a yield of 73 mol% when 1-methoxy-4-(1-methylethyl)benzene
was oxidised for 3 h at 60°C in acetonitrile as a solvent in the presence of NHPI. 1-(4-Methoxyphenyl)ethanone with high selectivity
up to 68–75 mol%, but low yield amounting to 11 mol% was obtained when 1-methoxy-4-(1-methylethyl)benzene was oxidised in
the presence of the NHPI/Cu(II) system at 120°C.
相似文献
63.
Aequationes mathematicae - For a family $$(\mathscr {A}_x)_{x \in (0,1)}$$ of integral quasi-arithmetic means satisfying certain measurability-type assumptions we search for an integral mean K such... 相似文献
64.
Dawid Maliszewski Agnieszka Wrbel Beata Kolesiska Justyna Frczyk Danuta Drozdowska 《Molecules (Basel, Switzerland)》2021,26(13)
A series of new analogs of nitrogen mustards (4a–4h) containing the 1,3,5-triazine ring substituted with dipeptide residue were synthesized and evaluated for the inhibition of both acetylcholinesterase (AChE) and β-secretase (BACE1) enzymes. The AChE inhibitory activity studies were carried out using Ellman’s colorimetric method, and the BACE1 inhibitory activity studies were carried out using fluorescence resonance energy transfer (FRET). All compounds displayed considerable AChE and BACE1 inhibition. The most active against both AChE and BACE1 enzymes were compounds A and 4a, with an inhibitory concentration of AChE IC50 = 0.051 µM; 0.055 µM and BACE1 IC50 = 9.00 µM; 11.09 µM, respectively. 相似文献
65.
Nowicka Beata Burgess John Parsons Simon A. Samotus Alina Szklarzewicz Janusz 《Transition Metal Chemistry》1998,23(3):317-319
Solvatochromism of the [Mo(CN)3O(phen)]− ion has been studied. Solvent effects on pressure dependence (up to 1.25 kbar) of wavelengths of maximum absorption for charge-transfer
bands of several molybdenum(IV) and tungsten(IV) complexes, [M(CN)3O(diimine)]− (M = Mo or W), are described. The effects of applied pressure are larger for less polar unstructured solvents than for highly
polar hydrogen-bonded solvents.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
66.
Jerzy Golimowski Beata Krasnodbska Eugeniusz Najdeker 《Fresenius' Journal of Analytical Chemistry》1995,352(6):544-546
The differential pulse single-sweep voltammetric technique with hanging mercury drop electrode was used for the determination of Cr(III). The determination was carried out in 0.2 mol/l sodium acetate as supporting electrolyte. The reduction peak of Cr(III) was recorded at –1.5 V vs. Ag/AgCl reference electrode. The relative standard deviation was 3% for Cr concentrations in the range of 0.4 mol/l. The determination of impurities (Cd, Cu, Pb and Zn) in fresh and overworked galvanic baths using anodic stripping voltammetry in the differential pulse mode is also described. 相似文献
67.
The electronic band structure and magnetic properties of iron phthalocyanine (FePc) monolayer were investigated by using the first-principles all-electron full-potential linearized augmented plane wave energy band method. It is found that the ferromagnetic FePc monolayer is energetically more stable than the paramagnetic one. The exchange interaction, which splits the majority and minority bands, influences strongly on the electronic structure near the Fermi level (EF). Magnetic moment of the central Fe atom is calculated to 1.95 μB. The range of the positive polarization of Fe site is larger in the out-of-plane than in the in-plane direction. The FePc ligand remains paramagnetic. The presence of states at EF indicates the metallic character of FePc monolayer both for the paramagnetic and ferromagnetic states. However, the large density of states at EF of the majority spins in the ferromagnetic state is expected to cause a phase transition to insulating antiferromagnetic state from the metallic ferromagnetic one. 相似文献
68.
Beata Bia?ek 《Surface science》2006,600(8):1679-1683
The structural end electronic properties of emeraldine base (EB) dimers interacting with a single Pd atom is investigated within Hartree-Fock with 6-31g(d, p) basis set for non-metal atoms, and 3-21g for Pd. It was found that Pd0 might create a stable complex with EB fragments. The influence of the Pd presence on the electronic structure of EB dimers is examined through an analysis of the total density of states and the crystal orbital overlap population (COOP). 相似文献
69.
Pawluc P Marciniec B Hreczycho G Gaczewska B Itami Y 《The Journal of organic chemistry》2005,70(1):370-372
Symmetrical 1,1-bis(silyl)ethenes have been easily prepared via ruthenium complex-catalyzed silylative coupling cyclization of 1,2-bis(dimethylvinylsiloxy)ethane to give 2,2,4,4-tetramethyl-3-methylene-1,5-dioxa-2,4-disilacycloheptane with excellent selectivity and good yield, followed by its reaction with Grignard reagents. The cyclic product can also be effectively transformed into cyclic carbosiloxane, 2,2,4,4,6,6,8,8-octamethyl-3,7-dimethylene-1,5-dioxa-2,4,6,8-tetrasilacyclooctane. 相似文献
70.
The effect of stress conditions on the concentrations of secondary metabolites were examined during various developmental stages of Papaver somniferum plants. P. somniferum plants were grown in laboratory conditions (Budakalász). The experiment consisted of 22 treatments. Significantly different alkaloid contents can be observed under different stress conditions. In general, the alkaloid contents of plants are very low; therefore, a highly sensitive and reliable method has to be developed for analysis. The amount of alkaloids was measured by 2 separation and detection techniques. Accuracy of the thin-layer chromatography method for quantitative analysis is limited. Without purification of samples the background is too noisy. Column liquid chromatography is a sensitive and relatively inexpensive method that allows precise quantitative determination of the alkaloid content. 相似文献