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  • 1
    Electronic Resource
    Electronic Resource
    Conformational analysis 29: Preparation and1H and13C NMR, FTIR, MS, and crystallographic conformational and configurational study of 3-Oxo-1,3-oxathiane and its monomethyl derivatives (1993)
    Springer
    Structural chemistry 4 (1993), S. 203-210 
    Details
    ISSN: 1572-9001
    Keywords: Conformational analysis ; X-ray crystallography ; 3-oxo-1,3-oxathianes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract 3-Oxo-1,3-oxathiane (1) and its monomethyl derivatives were prepared by oxidation of the corresponding 1,3-oxathianes. The structural analysis was carried out by1H and13C NMR, FTIR, and mass spectrometry. At 298 K compound1 was a 1 ∶ 1 (at 173 K a 3 ∶ 1) mixture of the SO(ax) and SO(eq) chair forms. The major oxidation products of methyl 1,3-oxathianes attained exclusively the SO(ax), Me(eq) chair forms except that of the 5-methyl derivative, which consisted of 7% of the SO(eq), Me(ax) chair conformation in CDCl3 solution. The minor products of oxidation existed in anancomeric SO(eq), Me(eq) chair conformations. The oxidation of 2-methyl- 1,3-oxathiane, however, led to 3,3-dioxo derivative (6) in addition to thetrans [SO(eq)] monoxide. The crystal structures of6 andtrans-3-oxo-5-methyl-1,3-oxathiane were solved by X-ray diffractometry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00679347
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  • 2
    Electronic Resource
    Electronic Resource
    Mass spectral fragmentation reactions of some stereoisomeric cyclic β-amino acids under electron and chemical ionization (1993)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 7 (1993), S. 1121-1125 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Mass spectral fragmentations of two cyclopentane, four cyclohexane/ene and four norbornane/ene ß-amino acids were studied under electron ionization by low-resolution, high-resolution, metastable ion analysis and collision-induced dissociation techniques. All stereoisomeric compounds gave rise to identical 70 eV electron-ionization mass spectra. The major fragmentation pathway for the saturated compounds began as an α-cleavage reaction with respect to the nitrogen atom. For the unsaturated compounds, a retro-Diels-Alder reaction was favoured. In addition to a normal retro-Diels-Alder fragmentation reaction, the norbornene compounds underwent a retro-Diels-Alder fragmentation reaction accompanied by the migration of one hydrogen atom. In the case of the chemical ionization mass spectra, differences between stereoisomers were observed only under methane chemical ionization, where monocyclic trans isomers decomposed more readily than the corresponding cis isomers. All the [M + H]+ ions decomposed mainly by dehydration and deamination reactions. The fragmentation in the chemical-ionization ion source resulted in the same elimination ratio [M + H — H2O]/{[M + H — H2O] + [M + H — NH3]} as observed under kinetic control in the collision region.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290071213
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  • 3
    Electronic Resource
    Electronic Resource
    Electron-impact induced fragmentations of some quinazolinediones and benzoxazinones (1993)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 7 (1993), S. 374-377 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Mass spectral fragmentations of 3-substituted 2,4(1H,3H)-quinazolinediones, 2-phenylimino-4H-3,l-benzoxazin-4-ones and 2-thioxo-2,3-dihydroquinazolidin-4(1H)-one were examined using metastable-ion analy sis and exact mass measurements. The isomeric compounds were easy to distinguish from their mass spectra. For quinazolinediones, the most surprising feature was the loss of CO2 showing that a rearrangement due to anilino migration must occur in these compounds. In comparison, the benzoxazinones showed no elimination of carbon dioxide.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290070512
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  • 4
    Electronic Resource
    Electronic Resource
    Mass spectral fragmentation of some cycloalkane-condensed 4,5-dihydro-3(2H)-pyridazinones and 4,5-dihydro-6H-1,2-oxazin-6-ones (1994)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 8 (1994), S. 1021-1025 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The electron ionization mass spectra of 10 cycloalkane-condensed 4,5-dihydro-3(2H)-pyridazinones and four cycloalkane-condensed 4,5-dihydro-6H-1,2-oxazin-6-ones were studied. The molecular ions of these compounds were very stable and in most cases formed the base peaks of the spectra. Otherwise the spectra of compounds having different fused cycloalkane rings deviated considerably from each other. The spectra of cis- and trans-fused cyclohexane derivatives showed characteristic differences.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290081223
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  • 5
    Electronic Resource
    Electronic Resource
    Electron ionization fragmentation of some isoindolone derivatives (1994)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 8 (1994), S. 858-862 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The electron ionization mass spectra of eleven isoindolone derivatives are reported. The molecular ions of these compounds were stable, some of them even very abundant (8-29% of the total ion current). There were many ions common to all or most of the compounds studied, although the abundances varied markedly from case to case. The base peak varied also from compound to compound. The most important ions common to almost every compound were [M - (CH2)iXH]+ (ions ai; i=1-4), [M - C7H7]+ (ion b) and the ion pattern [c - H], c and [c + H] corresponding to the loss of fused carbocycle together with the carbonyl function. These ions are caused by α-cleavages and inductive dissociations of the bonds of the molecular ion in respect to the hetero atoms X and/or N.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290081013
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  • 6
    Electronic Resource
    Electronic Resource
    Aromatische Sulfenylchloride, IX. Herstellung, Oxidation und spektroskopische Untersuchung von 1-substituierten (5-Tetrazolyl)aryldisulfiden (1974)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 107 (1974), S. 299-304 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Aromatic Sulfenyl Chlorides, IX. Preparation, Oxidation, and Spectroscopic Investigation of 1-Substituted 5-Tetrazolyl Aryl Disulfides1-Substituted 5-tetrazolyl mesityl disulfides were synthesized which on oxidation with hydrogen peroxide gave disulfide S2, S2-dioxides (thiolsulfonates). The structure of these as well as that of the 1-substituted 5-tetrazolyl p-tolyl disulfide S2, S2-dioxides synthesized earlier was elucidated by means of their i. r. and n. m. r. spectra. The supposed structures have been established by synthesis.
    Notes: Es wurden 1-substituierte (5-Tetrazolyl)mesityldisulfide hergestellt, welche zu Disulfid-S2, S2-dioxiden (Thiosulfonate) oxidiert wurden. Deren Struktur und die der früher hergestellten 1-substituierten (5-Tetrazolyl)p-tolyldisulfid-S2, S2-dioxide wurde anhand ihrer IR- und NMR-Spektren wahrscheinlich gemacht. Die angenommenen Strukturen wurden durch Synthese bewiesen.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19741070135
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  • 7
    Electronic Resource
    Electronic Resource
    Stereochemische Untersuchungen, 771).  -  Gesättigte Heterocyclen, 641). Synthese von gesättigten Methylen-überbrückten 1,3-Benzoxazinen (1984)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 3205-3210 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Stereochemical Studies, 771).  -  Saturated Heterocycles, 641). Synthesis of Saturated Methylene-Bridged 1,3-BenzoxazinesThe aminomethylbicyclanol 3, obtained from the cycloadduct 4 of norbornene (1) and trichloroacetyl isocyanate, furnished the 1,3-oxazin-2-one 7, 1,3-oxazine-2-thione 8 and 1,3-oxazines 2a-d. The exo-exo- (10, 12) and endo-endo-1,3-oxazin-4-ones (11, 13) were prepared from the 3-hydroxy-2-carboxamides 5 and 9. Structure of these rigid tricyclic systems were proved by 1H and 13C NMR spectroscopy.
    Notes: Aus dem Cycloaddukt 4 von Norbornen (1) und Trichloracetylisocyanat wurde der Aminoalkohol 3 hergestellt und daraus das tricyclische 1,3-Oxazin-2-on 7, bzw. 1,3-Oxazin-2-thion 8 und die 1,3-Oxazin-Derivate 2a-d synthetisiert. Die mit Norbornan anellierten exo-exo- (10 und 12) bzw. endo-endo-1,3-Oxazin-4-one (11 und 13) wurden aus den 3-Hydroxy-2-carboxamiden 5 und 9 erhalten. Die Struktur der tricyclischen kondensierten Systeme mit starrem Gerüst wurde durch 1H- und 13C-NMR-Spektroskopie bewiesen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19841171106
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  • 8
    Electronic Resource
    Electronic Resource
    Tautomerism and electron impact mass spectra of pyrimidin-4(3H)- and -4(1H)-ones (1990)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 25 (1990), S. 115-118 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A mass spectrometric identification and differentiation of pyrimidin-4(3H)- and -4(1H)-ones was carried out. N-Substitution at position 1 or 3 made the distinction of the two sets of compounds very easy because of their characteristic fragmentation pathways. Most interesting were the spectra of the N-unsubstituted derivatives, which illustrated a predominance of the two possible NH tautomers in relation to the 4-hydroxy structure.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210250206
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  • 9
    Electronic Resource
    Electronic Resource
    Mass spectrometric study of some cycloalkane/ene-condensed 2-thioxo-2935556-pyrimidin-4(1H)-ones and cycloalkane/ene-condensed [l,3] thwzino [3,2-a]-pyrimidinones under electron impact (1991)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 26 (1991), S. 493-497 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectra of four cycloalkane/ene cis- and trans-condensed 2-thioxo-2,3,5,6-tetrahydropyrimidin-4(1H)-ones and the corresponding cycloalkane/ene cis- and trans-condensed [l,3]thiazino[3,2-a]pyrimidinones were measured. Fragmentation pathways were confirmed by metastable ion analyses and exact mass measurements. The bicyclic isomers were easy to distinguish from each other, whereas the corresponding tricyclic isomeric adducts gave fairly similar mass spectra, owing to their favoured reiro-Diels- Alder fragmentations accompanied by the migration of one or two hydrogen atoms.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210260522
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  • 10
    Electronic Resource
    Electronic Resource
    Electron and chemical ionization mass spectrometry in stereochemical differentiation of some 1,3-amino alcohols (1994)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 29 (1994), S. 126-132 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mass spectral fragmentations of two cyclopentane, eight cyclohexane and four norbornane/one 1,3-amino alcohols were studied under electron ionization (EI) by low-resolution, high-resolution, metastable ion analysis and collision-induced dissociation (CID) techniques. All stereoisomeric compounds gave rise to identical 70 eV EI mass spectra. However, the spectra of positional isomers clearly differed. The main fragmentation pathway for the saturated compounds began as an α-cleavage reaction with respect to the nitrogen atom. For the norbornene compounds a retro-Diels - Alder reaction was favoured. Relative to the aminomethyl-substituted compounds the fragmentation patterns for the compounds having the amino group connected directly to the ring were more complicated. The chemical ionization (CI) mass spectra were recorded using ammonia, isobutane, methane, dichloromethane and acetone as reagent gas. From the norbornane/One compounds the di-exo isomers decomposed more easily than the di-endo isomers with most of the reagent gases used. Differences between stereoisomers were observed directly only under methane CI. The decomposition products of the [M + H]+ ions generated under ammonia and isobutane CI were studies by recording their CID mass spectra. These spectra allowed the differentiation of the stereoisomers, at least to some extent.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210290303
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