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931.
Frańska M Zgoła A Rychłowska J Szymański A Łukaszewski Z Frański R 《European journal of mass spectrometry (Chichester, England)》2003,9(3):165-173
Mass spectrometric behaviour of mono- and di-carboxylated polyethylene glycols (PEGCs and CPEGCs) and carboxylated octylphenol ethoxylates (OPECs) are discussed. The tendency for ionisation (deprotonation, protonation and cationisation by alkali metal cations) of carboxylated PEGs was compared with that of non-carboxylated correspondents by using both secondary ion mass spectrometry (SIMS) and electrospray ionisation (ESI). The fragmentation of the PEGCs and CPEGCs is discussed and also compared with their neutral correspondents, PEGs. The B/E mass spectra were recorded, using secondary ion mass spectrometry as a method for generation, for deprotonated and protonated molecules and molecules cationised by alkali metal cations. The fragmentation behaviour of PEGs is found to be different from that of CPEGCs, The presence of carboxylic groups may be confirmed not only by the determination of molecular weights of the ethoxylates studied, but also on the basis of the fragment ions formed. The metastable decomposition of the [OPEC-H](-) ions proceed through the cleavage of the bond between the octylphenol moiety and the ethoxylene chain leading to the octylphenoxy anions. It permits determination of the mass of the hydrophobic moiety of the studied carboxylated alkylphenol ethoxylate. ESI mass spectra recorded in the negative ion mode were found to be more suitable for the determination of the average molecular weight of carboxylated ethoxylates than SI mass spectra. 相似文献
932.
Jiménez JC Chavarría B López-Macià A Royo M Giralt E Albericio F 《Organic letters》2003,5(12):2115-2118
[reaction: see text] A solid-phase method for the synthesis of tentoxin has been developed. Two key steps-dehydration and N-alkylation-are carried out while the peptide is anchored to the resin. The method, which has been validated by the preparation of a library of tentoxin analogues, should be applicable to the generation of further libraries that have the tentoxin scaffold structure, as well as other structures containing N-alkylated didehydroamino acids. 相似文献
933.
CH_3自由基和O(~3P)反应机理的量子化学研究 总被引:4,自引:0,他引:4
用分子轨道从头计算MP2(full)方法和密度泛函理论(DFT)中的B3LYP方法 研究了CH_3自由基和三线态O原子反应的微观机理,优化得到了反应途径上的反应 物、过渡态、中间体和产物的几何构型,通过振动分析对过渡态和中间体构型进行 了确认,在G3不平上计算了能量,同时用经典过渡态理论对该反应的绝对速率常数 进行了理论计算。研究结果表明:CH_3自由基与O(~3P)反应有四条不同的放热反 应通道,主反应通道为IM1→TS1→CH_2O + H,同时反应可彻底裂解生成CO, H_2 及H。 相似文献
934.
Four new supramolecular compounds of Cu(II)-Ni(II) have been synthesized and characterized: [Cu(Me(2)oxpn)Ni(mu-NCS)(H(2)O)(tmen)](2)(ClO(4))(2) (1), [Cu(Me(2)oxpn)Ni(mu-NCS)(H(2)O)(tmen)](2)(PF(6))(2) (2), [Cu(oxpn)Ni(mu-NCS)(NCS) (tmen)](n) (3), and [Cu(Me(2)oxpn)Ni(mu-NCS)(NCS)(tmen)](n) (4), where oxpn = N,N'-bis(3-aminopropyl)oxamidate, Me(2)oxpn = N,N'-bis(3-amino-2,2'-dimethylpropyl)oxamidate, and tmen = N,N,N',N'-tetramethylethylenediamine. Their crystal structures were solved. Complexes 1 and 2 have the same tetranuclear cationic part but a different counteranion. The cationic part consists of two [Cu(Me(2)oxpn)Ni] moieties linked by SCN(-) bridged ligands and intra-tetranuclear hydrogen bonds. In the case of complex 3, a two-dimensional system was built, the thiocyanate ligand linking the dinuclear units gives a chain, and the chains are linked together by hydrogen bonds; intrachain hydrogen bonds are also present. For complex 4, the thiocyanate ligands produce intermolecular linkages between the dinuclear entities, giving a one-dimensional system; intrachain hydrogen bonds are also present. The magnetic properties of the four complexes were studied by susceptibility measurements vs temperature. DFT calculations were made to study the contribution of the SCN(-) and hydrogen bond bridges in the magnetic coupling. 相似文献
935.
Trapping centers related to P+ and B+ ions implanted in the SiO2 layer as well as traps introduced into SiO2 during boron implantation through the oxide into the silicon substrate have been investigated. The internal photoemission method has been used to estimate their capture cross section and total densityN
t
. 相似文献
936.
Izabela Jendrzejewska Tomasz Goryczka Ewa Pietrasik Joanna Klimontko Josef Jampilek 《Molecules (Basel, Switzerland)》2020,25(24)
Studies carried out by X-ray and thermal analysis confirmed that acetaminophen (paracetamol), declared by the manufacturers as an Active Pharmaceutical Ingredient (API), was present in all studied medicinal drugs. Positions of diffraction lines (2θ angles) of the studied drugs were consistent with standards for acetaminophen, available in the ICDD PDF database Release 2008. values were lower than 0.2°, confirming the authenticity of the studied drugs. Also, the values of interplanar distances dhkl for the examined samples were consistent with those present in the ICDD. Presence of acetaminophen crystalising in the monoclinic system (form I) was confirmed. Various line intensities for API were observed in the obtained diffraction patterns, indicating presence of the preferred orientation of the crystallites in the examined samples. Thermal analysis of the studied substances confirmed the results obtained by X-ray analysis. Drugs containing only acetaminophen as an API have melting point close to that of pure acetaminophen. It was found that presence of other active and auxiliary substances affected the shapes and positions of endothermal peaks significantly. A broadening of endothermal peaks and their shift towards lower temperatures were observed accompanying an increase in the contents of additional substances being “impurities” in relation to the API. The results obtained by a combination of the two methods, X-ray powder diffraction (XRPD) and differential scanning calorimetry/thermogravimetry (DSC/TGA), may be useful in determination of abnormalities which can occur in pharmaceutical preparations, e.g., for distinguishing original drugs and forged products, detection of the presence of a proper polymorphic form or too low content of the active substance in the investigated drug. 相似文献
937.
Palazón J. Gálvez J. García G. López G. 《Journal of Thermal Analysis and Calorimetry》1987,32(2):645-652
The preparations of the nickel-morpholine (Morph) complexes Ni(NO2)2·3Morph and Ni(ClO4)2·4Morph·2H2O are described. The thermal treatment of this perchlorate and of NiSO4·2Morph led to the isolation of Ni(ClO4)2·2Morph·2H2O and NiSO4·Morph. The magnetic moments, diffuse reflectance spectra and infrared spectra of these compounds are all compatible with a pseudo-octahedral environment around the nickel atom.
The authors are indebted to Consejeria de Cultura y Educación de la Comunidad Autónoma de Murcia for financial support. 相似文献
Zusammenfassung Die Darstellung der Nickel-Morpholin(Morph)-Komplexe Ni(NO2)2·3Morph und Ni(ClO4)2·4Morph·2H2O wird beschrieben. Die thermische Behandlung dieses Perchlorates und von NiSO4·2Morph ergibt Ni(ClO4)2·2Morph·2H2O und NiSO4Morph. Magnetisches Moment sowie diffuse Reflektionsspektren und Infrarotspektren dieser Verbindungen sind kompatibel mit einer pseudooktaedrischen Koordination des Nickelatoms.
, () : Ni(NO2)2·, NiSO4·2 Ni(ClO4)2·4·2H2O. NiSO4· Ni(ClO4)2·2·2H2O. , , .
The authors are indebted to Consejeria de Cultura y Educación de la Comunidad Autónoma de Murcia for financial support. 相似文献
938.
Summary The virial theorem for a molecule in the relativistic clamped-nuclei approximation is derived. The individual energy contributionsA (momentum energy),B (mass energy),T=A+B (kinetic energy) andV (potential energy) are expressed in terms ofE, E/R (derivate w.r.t. the nuclear coordinates) and the relativistic correction E/2 (derivative w.r.t. Sommerfield's fine-structure constant ). IfE and E/R are known as functions of , then all individual energy terms are also known as functions of . As an example, numerical results for H
2
+
are presented. The relativistic and nonrelativistic potential energy curves and the paradoxical behavior of their different contributions are analyzed and interpreted in both the largeR and shortR ranges.Dedicated to Professor W. Kutzelnigg on the occasion of his 60th birthday 相似文献
939.
W. Ryba-Romanowski S. Go
b G. Dominiak-Dzik W. A. Pisarski D. Podsiada Z. Czapla 《Journal of Molecular Structure》1998,450(1-3):219-222
Chromium doped (CH3)2NH2Al(SO4)2·6H2O (DMAAlS) and (CH3)2NH2Ga(SO4)2·6H2O (DMAGaS) single crystals were grown and investigated using the methods of optical spectroscopy. It was found that the Cr3+ ions in the two crystals are situated in a strong crystal field in which the 2E state is the lowest. The single narrow R-line associated with the 2E–4A2 phosphorescence of Cr3+ in DMAAlS in a ferroelectric phase indicates an undistorted octahedral site, whereas important distortion of Oh symmetry and structural disorder was inferred from spectral data obtained with DMAGaS:Cr3+ in a low temperature phase. Results of optical investigation are discussed taking into account the structural data. 相似文献
940.
Ksenija Radotic Smilja Todorovic Joanna Zakrzewska Milorad Jeremic 《Photochemistry and photobiology》1998,68(5):703-709
The structure of the polymer synthesized by UV irradiation of coniferyl alcohol was studied, using UV-visible, Raman, IR, H-NMR and 13C-NMR spectroscopy. The photochemical polymer was compared with the structure of the polymer obtained by peroxidase-catalyzed polymerization of coniferyl alcohol. General similarity of the spectra of the two polymers was shown. However, differences in the fine structure of particular regions of the NMR spectra, as well as in certain bands in the Raman and IR spectra, could be explained through the various bond types and organization within the polymers. These results are consistent with molecular mass distribution of the polymers. Two fractions of enzymatic polymer correspond to the main two fractions of photochemical polymer. The later polymer has additional fractions that are probably the main reason for the observed spectral differences. 相似文献