ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Analytical Chemistry and Spectroscopy  (3)
  • Wiley-Blackwell  (3)
  • American Geophysical Union
  • National Academy of Sciences
  • 2020-2022
  • 1975-1979  (3)
Collection
Publisher
  • Wiley-Blackwell  (3)
  • American Geophysical Union
  • National Academy of Sciences
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 7 (1975), S. 355-357 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have determined the magnitudes of all possible four-, five- and six-bond HH couplings in four 2-pyrone derivatives. Substituents exert a negligible effect on the couplings. The allylic couplings are position-specific (J34 = 1·2; J45 ≤ 0·2; J56 = 0.8) and the observed pattern of alternating magnitudes is indicative of π-bond fixation. The allylic couplings can be translated into π-bond orders which agree well with results of recently published SCF-MO calculations on 2-pyrone. Finally, comparison of long range coupling constant data for 4,6-dimethyl-2-pyrone with those for related cyclic anhydrides and trans-1,3-pentadiene further supports the picture of 2-pyrone as a slightly perturbed butadiene, in agreement with extensive chemical and physical evidence.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 13C n.m.r. spectra of 11 derivatives of 2,3-dimethylenenorbornane, 1-11, of 5 derivatives of 2,3-dimethylene-7-oxanorbornane, 12-16, and of 2,3,5,6-tetramethylene-7-oxanorbornane (17) have been measured and the chemical shifts have been assigned. The effects of 1-methyl, 5-hydroxy, 5-acetoxy, 5-para-bromobenzenesulphonyloxy and 5-keto substituents on the olefinic carbons of the s-cis-butadiene group are compared with the same substituent effects reported for model compounds. Apparent linear correlations between the reciprocals of the V←N transition energies of the butadiene chromophores and the differences of the chemical shifts ΔδC between the quaternary and methylene olefinic carbons are found for the dienes 1-3, 12-14, butadiene and 2,3-dimethylbutadiene. The ΔδC of the olefinic carbons of the tetraene 17 also falls on the correlation line if the average of the two absorption hands at 250 and 228 nm is taken for the V←N transition energy of this compound. The chemical shift of the carbon of the methano bridge H2C-7 is almost insensitive to the presence of one or two methylene groups at C-2,3, in contrast with the downfield shift of 10-14 ppm observed when an endocyclic double bond is introduced into the norbornane skeleton.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    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 electron impact induced decomposition of 1,6-methano[10]annulene and of its bridge substituted derivatives has been investigated in view of a possible climination of a carbene and formation of ionized naphthalene. While carbene elimination is not observed with the parent hydrocarbon (〈0.5% rel. int.), it is a prominent fragmentation path for its 11-halogen and 11,11-dihalogen derivatives. Elimination of the bridge is observed also with 1,6-methano[10]annulenes carrying C-substituents at C-11. It cannot be determined, however, whether the neutral particle lost is a carbene or a rearranged species. The analogy between thermal and electron impact decomposition is commented upon.
    Notes: Der elektronenstoß-induzierte Zerfall von 1,6-Methano[10]annulen und Derivaten mit Brücken-Substituenten (11-Stellung) wurde im Hinblick auf die Möglichkeit untersucht, daß die Brücke unter gleichzeitiger Bildung von ionisiertem Naphthalin als Carben eliminiert wird. Während die Carbenabspaltung beim 1,6-Methano[10]annulen selbst nicht beobachtet wird (〈0,5% rel. Int.), ist diese bei seinen 11-Halogen- und 11,11-Dihalogen-Derivaten ein wichtiger Fragmentierungsweg. Komplette Eliminierung der Brücke wird auch bei 1,6-Methano[10]annulen mit C-Substituenten in 11-Stellung beobachtet, doch läß sich hier nicht entscheiden, ob die Brücke als Carben order als umgelagerte neutrale Spezies austritt. Auf die Parallelität zwischen thermischem und elektronenstoß-induzierten Verhalten der 1,6-Methano[10]annulene wird hingewiesen.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...