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  • 1
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 14 (1979), S. 244-253 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The very complex isomerization patterns of methoxy and carbomethoxy substituted cycloalkanes (3- to 7-membered rings) have been investigated using collisional activation, metastable ion characteristics and field ionization kinetics. The extent of isomerization depends on both the ring size and the substituent. Irrespective of the electronic properties of the substituent, ring opening involves exclusively the C-1—C-2 bond whereby linear alkene radical cations are formed. In the case of OCH3- and COOCH3 substituents the position of the resulting double bond (terminal or α,β-unsaturated) is determined more by the ring size of the precursor molecules and less by the electronic properties of the substituents. Contrary to these findings alklyl substituted cycloalkanes (3- to 5-membered rings) rearrange exclusively to terminal alkene radical cations. The barrier for double bond isomerization seems to be substantially influenced by substituents.
    Notes: Unter Benutzung mehrerer Techniken, wie Stoßaktivierung, Charakteristik metastabiler Ionen und Feldionisationskinetik, wird das äußerst komplexe Isomerisierungsverhalten von methoxy- und caarbomethoxysubstituierten Cycloalkanen (drei-bis siebengliedrege Ringe) analysiert. Das Ausmaß der Isomerisierung hängt sowohl von der Ringgröße als auch vom Substituenten ab, während die Ringöffnung unabhängig von den elektronischen Eigenschaften der Substituenten immer die C-1—C-2-Bindung betrifft. Hierbei werden ausschließlich lineare Alken-Radikalkationen erzeugt. Bei OCH3- und COOCH3-Substituenten wird die Lage der resultierenden Doppelbindung terminal oder α,β-ungesättigt hauptsächlich durch die Ringgröße des Cycloalkan-Molekülions und weniger durch den Substituenten beeinfluß. Alkylsubstituierte Cycloalkane (drei- bis fünfgliedrige Ringe) lagern sich allerdings nur zu terminalen Alken-Radikalkationen um. Die Barriere der Doppelbindungswanderung scheint vom Substituenten abhängig zsu sein.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 17 (1986), S. 51-53 
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Raman excitation profiles (REPs) for bands of carotenoid and chlorophyll b (Chl b) from whole cells of green algae at low temperatures are presented. In addition to preventing thermal destruction of the samples during long-term irradiation, the use of a double channel surface scanning technique allowed the recording of the Raman spectrum of a non-resonating substance such as acetone suitable as an intensity reference at the same time. The measured REPs are compared with the absorption spectrum of whole cells at low temperatures.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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