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  • 1
    Electronic Resource
    Electronic Resource
    Degradative Pathways for Aqueous Chlorination of Orcinol (1994)
    s.l. : American Chemical Society
    Environmental science & technology 28 (1994), S. 606-613 
    Details
    ISSN: 1520-5851
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/es00053a012
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    A Study of the Mechanism of Platinum(II)/Tin(II) Dichloride Mediated Hydrogenation of Alkynes and Alkenes Employing Parahydrogen-Induced Polarization (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 1915-1923 
    Details
    ISSN: 1434-1948
    Keywords: Hydrogenations ; Parahydrogen ; Platinum ; Alkynes ; Alkenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mechanism of hydrogenation of alkynes catalyzed by the [(PR3)2PtHX]/SnX2 system (PR3 = PPh3, PMePh2; × = Cl, Br) has been studied by means of parahydrogen-induced polarization of 1H spectra (PHIP). Dihydride intermediates confirming the stepwise hydrogenation at room temperature were observed when the reaction was run in acetone. The obtained 1H-PHIP spectra, together with NMR data for related species, are consistent with the formulation of these intermediates as cis-[H2Pt(PR3)(SnX3)(σ-alkenyl)(acetone)], where the σ-alkenyl ligand originates from an insertion reaction of the alkyne (1-phenyl-1-propyne, 1-phenyl-1-butyne, diphenylacetylene, 3,3-dimethylbutyne). At elevated temperatures, the hydrogenation in acetone proceeds as a cis-synchronous transfer of the two hydrogen atoms of parahydrogen to the substrate molecule. A mechanism for this synchronous hydrogenation is suggested.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    Collision-induced dissociation study of cyclization of α-diazo-ω-arylsulphonylaminoalkan-2-ones (1992)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 27 (1992), S. 730-735 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The collision-induced dissociation mass-analysed ion kinetic energy (CID MIKE) spectra (electron impact and chemical ionization) of five α-diazo-ω-arylsulphonylaminoalkan-2-ones and corresponding N-arylsulphonylazetidin-3-ones and N-arylsulphonylpyrrolidin-3-ones were studied. The [M — N2]+· and [MH — N2]+ ions of two types of the diazo ketones provide CID MIKE spectra similar to those of the corresponding M+· and MH+ of the heterocyclic compounds, i.e. a cyclization analogous to that in solution takes place. For the other three types of diazo compounds the Wolff rearrangement prevails in both the gas and liquid phases. The effect of the substituents on the cyclization process was studied. The data obtained permit the results of acid-catalysed cyclization of similar diazo ketones to be predicted on the basis of their CID MIKE spectra. Chemical ionization provides a closer similarity with reactions in solution than electron impact ionization, which can be rationalized by the protonation of the diazo ketone molecule being the driving force of the cyclization reaction either in solution or in the ion source of a mass spectrometer.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210270615
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Linear dependence of 1J13C, 199Hg) and 2J(1H, C,199Hg) for dibenzylmercury in various solventsContribution No. 5478. (1977)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 9 (1977), S. 555-556 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 1J(13C, 199Hg) spin-spin coupling constants have been studied for dibenzylmercury in various solvents. A linear correlation was found between 1J(13C, 199Hg) and the 2J(1H, C, 199Hg) constants obtained earlier for the same solutions.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270090914
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    The electron impact-induced cyclization of o-carboxy- and o-carboxamidocyclopropylbenzenes (1989)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 24 (1989), S. 149-152 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The isomerization of M+ · of o-carboxy- and o-carboxamidocyclopropylbenzenes into five- and six-membered heterocycles due to the ortho effect has been demonstrated by means of electron impact mass spectra, high-resolution mass spectrometry data and metastable ion spectra. The criteria for the quantitative estimation of the degree of cyclopropane cyclization into these isomeric cycles were formulated. The nature and quantity of heterocyclic ions proved to be in good accord with the results for cyclization of the same cyclopropanes in the strong acid solutions.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210240302
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    Paper (German National Licenses)
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  • 6
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    Molecular Weight Characteristics of Humic Substances from Different Environments As Determined by Size Exclusion Chromatography and Their Statistical Evaluation (2003)
    ACS (American Chemical Society)
    In:  Environmental Science & Technology, 37 (11). pp. 2477-2485.
    Details
    Publication Date: 2020-09-18
    Description: Recorded molecular weights (MWs) for humic substances (HS) range from a few hundred to millions of daltons. For purposes of defining HS as a specific class of chemical compounds, it is of particular importance to ascertain if this broad range of MWs can be attributed to actual variability in molecular properties or is simply an artifact of the analytical techniques used to characterize HS. The main objectives of this study were (1) to establish if a preferential range of MWs exists for HS and (2) to determine any consistent MW properties of HS. To reach the goal, we have undertaken an approach to measure under standardized conditions the MW characteristics of a large set of HS from different natural environments. Seventy-seven humic materials were isolated from freshwater, soil, peat, and coal, such that each possessed a different fractional composition:  humic acid (HA), fulvic acid (FA), and a nonfractionated mixture of HA and FA (HF). Size exclusion chromatography (SEC) was used as the analytical technique to determine molecular weight characteristics. The MW distributions were characterized by number (Mn) and weight (Mw) average MW, and by polydispersity. The complete range of Mw values varied within 4.7−30.4 kDa. The maximum Mw values were observed for peat HF and soil HA, whereas the smallest weights were measured for river water HF. Maximum values of polydispersity (3.5−4.4) were seen for peat HF and soil HA, while much lower values (1.6−3.1) were found for all preparations isolated with XAD-resins. Statistical evaluation showed consistent Mw and Mn variations with the HS source, while polydispersity was mostly a function of the isolation procedure used. A conclusion was made that HS have a preferential range of MW values that could characterize them as a specific class of chemical compounds.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1021/es0258069
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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