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91.
The principal characteristics and products of thermal degradation of a commercial epoxy resin prepared by reaction of 2,2-bis(4′-hydroxy phenyl)propane (bisphenol-A) with 1-chloro-2,3-epoxy propane (epichlorhydrin) have been studied. The principal volatile products, acrolein, acetone and allyl alcohol, are formed at 280°C and, although cross-linking is detectable at 220°C, it only becomes significant at 320°C when the residual resin is brittle and insoluble. Decomposition of the cross-linked resin occurs above 340°C when phenolic compounds appear together with more complex products with higher molecular weights whose structures have been speculated upon from examination of their mass spectral characteristics. 相似文献
92.
Dicobalt octacarbonyl catalyzed silyl-hydroformylation of oxetanes can be controlled by the choice of trialkylsilane. Triethylsilane gives 1,4--silyl ethers while -butyl-dimethylsilane yields silyl enol ethers. 相似文献
93.
Guy Bouchoux Yannik Hoppiiliard Pascale Jaudon 《Journal of mass spectrometry : JMS》1987,22(2):98-102
Dissociative ionization of 1,2-epoxy n-alkanes gives rise to abundant [C4H7O]+ ions of structure [CH3OCHCHCH2]+. This conclusion is drawn from metastable ion analysis and from collisional activation spectra. This fragmentation involves the C? C ring opening and a 1,4-H migration leading to the corresponding enol ether [CH3OCHCHCH2R]+. precursor of [CH3OCHCHCH2]+ fragment. The same isomerization scheme applies to 1,2-epoxy methyl substituted alkanes and 2,3-epoxy n-alkanes. 相似文献
94.
A number of recent papers have considered ways in which molecular structure may be calculated when both the electrons and the nuclei are treated from the outset as quantum particles. This is in contrast to the conventional approach in which the nuclei initially have their positions fixed and so merely provide a potential for electronic motion. The usual approach is generally assumed to be justified by the 1927 work of Born and Oppenheimer. In this paper we discuss what precisely might be anticipated in the way of molecular structure from a mathematical consideration of the spectral properties of the full Coulomb Hamiltonian, to what extent the very idea of molecular structure might be dependent upon treating the nuclei simply as providing a potential and the extent to which the work of Born and Oppenheimer can be used to support this position. 相似文献
95.
Reinhard Haase Dorit S. Meinhold Berthold Thomas Edwin Weber Gerd Rheinwald 《Structural chemistry》2002,13(5-6):471-477
The crystal structures of inclusion compounds of 3,3-bis(9-hydroxy-9-fluorenyl)-2,2-binaphthyl host (1) and its chloro (2) or bromo (3) derivatives substituted in 2,7-positions of the fluorene units with acetone guests (1A–3A) were determined by X-ray studies as well as by 1H-CRAMPS solid-state NMR. Using this NMR technique allows identification of differently bound guest molecules due to their different chemical shifts caused by the influence of the ring current effects of the host aryl units. 相似文献
96.
Th. Weber E. Riedle H. J. Neusser 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1991,20(1):43-46
Sub-Doppler electronic spectra with hundreds of resolved rotational lines are now available for benzene-Ar dimers and trimers. From their analysis the structure of these clusters is precisely determined. The analysis of two bands, 6 0 1 and 16 0 2 , of C6H6 · Ar is presented in detail. It leads to accurate values of the van der Waals bond length in the electronic ground and excited state. The change in frequency upon clustering is found to be a factor of 17 larger for the overtone of the out-of-plane modev 16 than for the in-plane vibrationv 1. This can be tentatively explained by an interaction of the low frequency out-of-plane motion of the ring with the van-der-Waals motion of the Ar atom. 相似文献
97.
Kratzsch C Peters FT Kraemer T Weber AA Maurer HH 《Journal of mass spectrometry : JMS》2003,38(3):283-295
A liquid chromatographic/mass spectrometric assay with atmospheric pressure chemical ionization (APCI-LC/MS) is presented for the fast and reliable screening and identification and for the precise and sensitive quantification of 15 neuroleptic (antipsychotic) drugs and three of their relevant metabolites in plasma. It allows confirmation of the diagnosis of a neuroleptic overdose and monitoring of psychiatric patients' compliance. The neuroleptics amisulpride, bromperidol, clozapine, droperidol, flupenthixol, fluphenazine, haloperidol, melperone, olanzapine, perazine, pimozide, risperidone, sulpiride, zotepine and zuclopenthixol and the pharmacologically active metabolites norclozapine, clozapine N-oxide and 9-hydroxyrisperidone were extracted from plasma using solid-phase extraction and were separated on a Merck LiChroCART column with Superspher 60 RP Select B as the stationary phase. Gradient elution was performed using aqueous ammonium formate and acetonitrile. After screening and identification in the scan mode using the authors' new LC/MS library, the neuroleptics were quantified in the selected-ion mode. The quantification assay was fully validated. It was found to be selective and proved to be linear from sub-therapeutic to over therapeutic concentrations for all analytes. The corresponding reference levels are listed. The accuracy and precision data were within the required limits. The analytes were stable in frozen plasma for at least 1 month. The method was successfully applied to several authentic plasma samples from patients treated or intoxicated with various neuroleptics. The validated LC/MS assay has proved to be appropriate for the isolation, separation, screening, identification and quantification of various neuroleptics in plasma for clinical toxicology and therapeutic drug monitoring purposes. 相似文献
98.
Jean BourguignonUlf Bremberg Georges DupasKristina Hallman Lars HagbergLaurent Hortala Vincent LevacherSerghey Lutsenko Emmanuel MacedoChristina Moberg Guy QuéguinerFredrik Rahm 《Tetrahedron》2003,59(48):9583-9589
Chiral pyridinooxazoline, quinolinooxazoline, bis(oxazolino)pyridine (pybox), and bisoxazoline (box) derivatives containing crown ether residues were prepared. Some of the ligands were assessed in substrate binding studies and in palladium catalyzed allylic alkylations. 相似文献
99.
Syntheses of new sulfinylcinnolines, quinoxalines, quinazolines and phtalazines have been investigated starting from the appropriate halogenobenzodiazine derivatives. The latter were converted in one step to the corresponding sulfanyl benzodiazines which upon oxidation with m-CPBA led to the corresponding sulfoxide derivatives of benzodiazines in moderate to good yields. In parallel to this study, an improved method for the synthesis of 2-methylsulfinylquinoxaline starting from 2-sulfanylquinoxaline is also described and in the quinazoline series a synthetic route has been developed to prepare 2-tert-butyl-5-phenylsulfinylquinazoline with satisfactory yield as well as 2-tert-butyl-5-tert-butylsulfinyl-4(3H)-quinazolinone and 2-tert-butyl-8-tert-butylsulfinyl-4(3H)-quinazolinone. 相似文献
100.
[structure: see text] A series of ruthenium(II) complexes containing BINOL-based monodonor phosphorus ligands have been prepared and applied to the asymmetric catalysis of the hydrogenation of aryl/alkyl ketones. The best ligands for this application are those which contain an aromatic groups with either a methoxide or bromide on the ortho position. Using these ligands, alcohols with ee's of up to 99% are formed. 相似文献