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1978 (1)
1977 (1)
1976 (1)
1Author    Jerzy Sepiol, Zygmunt Kazimierczuk, David ShugarRequires cookie*
 Title    Tautomerism of Isoguanosine and Solvent-Induced Keto-Enol Equilibrium  
 Abstract    Ultraviolet and infrared absorption spectroscopy, in aqueous and non-aqueous media, have been employed to study the tautomerism of 9-substituted isoguanines, including the nucleoside iso­ guanosine. With the aid of a series of model compounds, it was shown that 9-substituted isogua­ nines, and isoguanosine, in aqueous medium are predominantly in the form N (1) H,2-keto-6-amino. In dioxane solution the tautomeric equilibrium is shifted in the direction of the enol form. The shift towards this form is accentuated for those analogues in which the exocyclic amino group is methylated. 
  Reference    (Z. Naturforsch. 31c, 361 [1976]; received May 3 1976) 
  Published    1976 
  Keywords    Isoguanine Analogues, Isoguanosine, Tautomerism, Tautomeric Equilibrium, Solvent Polarity 
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 TEI-XML for    default:Reihe_C/31/ZNC-1976-31c-0361.pdf 
 Identifier    ZNC-1976-31c-0361 
 Volume    31 
2Author    Requires cookie*
 Title    Beiträge zur Chemie der Pyrrolpigmente, X V II1  
 Abstract    Struktur-und konformationsanalytische Untersuchungen am chromophoren System der Bilivioline [Biladiene-(a.b)] On the Chemistry of Pyrrole Pigments, X V II Investigations of Structure and Conformation of the Chromophoric System of Biliviolines [Biladienes-(a,b)] H e i n z F a l k , S t e f a n G e r g e l y , K a r l G r u b m a y r u n d O t m a r H o f e r The {Z,Z)-configuration of the bilivioline chromophoric system was established in ­ vestigating an appropriate model compound by means of pK measurement, X H NMR spectroscopy Lanthanide ion induced shift technique, electron absorption spectroscopy and P P P calculations. Moreover a syn-syn conformation which is twisted at the a-methine single bond and planar within the pyrromethene unit (based on the concept of partial structures of bile pigments) of the molecule was deduced. 
  Reference    (Z. Naturforsch. 32b, 299—303 [1977]; eingegangen am 12. November 1976) 
  Published    1977 
  Keywords    !H NMR, Lanthanide Shifts, PP P calculations, UV, Tautomeric Equilibrium 
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 TEI-XML for    default:Reihe_B/32/ZNB-1977-32b-0299.pdf 
 Identifier    ZNB-1977-32b-0299 
 Volume    32 
3Author    Heinz Falk, Karl Grubmayr, Klaus ThirringRequires cookie*
 Title    Beiträge zur Chemie der Pyrrolpigmente, XXIII [1] Die Struktur eines Bilatrien-abc-Derivates im gelösten Zustande On the Chemistry of Pyrrole Pigments, XXIII [1] The Structure of a Bilatriene-abc Derivative in the State of Solution  
 Abstract    The (Z,Z,Z)-configuration of the mono-lactim-ether of an alkyl substituted bilatriene-abc, Etiobiliverdin-IV-y, was established for chloroform solutions. Moreover the confor-mation of this molecule is a helical one (syn-syn-syn) with a twist along the single bonds at the methine groups of approximately 20°. The two tautomeric lactam-forms with a proton on one or the other nitrogen atom of the pyrromethene subsystem are indistin-guishable by the methods used in this investigation: *H NMR pattern, Lanthanide induced shift technique and Nuclear Overhauser Effect measurements. 
  Reference    Z. Naturforsch. 33b, 924—931 (1978); eingegangen am 30. Januar 1978 
  Published    1978 
  Keywords    *H NMR, Lanthanide Shifts, Configuration, Conformation, Tautomeric Equilibrium 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0924.pdf 
 Identifier    ZNB-1978-33b-0924 
 Volume    33