Direct observation of the tautomeric forms of histidine in nitrogen-15 NMR spectra at low temperatures. Comments on intramolecular hydrogen bonding and on tautomeric equilibrium constants

1993 ◽  
Vol 115 (15) ◽  
pp. 6813-6819 ◽  
Author(s):  
Shauna Farr-Jones ◽  
Winona Y. L. Wong ◽  
William G. Gutheil ◽  
William W. Bachovchin
Keyword(s):  
Hydrogen Bonding ◽  
Direct Observation ◽  
Low Temperatures ◽  
Nmr Spectra ◽  
Equilibrium Constants ◽  
Intramolecular Hydrogen Bonding ◽  
Tautomeric Equilibrium ◽  
Tautomeric Forms ◽  
Intramolecular Hydrogen

2-Substituted and 2,6-disubstituted 1,4-benzoquinone 4-oximes ('p-nitrosophenols')

1969 ◽  
Vol 22 (5) ◽  
pp. 935 ◽  
Author(s):  
RK Norris ◽  
S Sternhell
Keyword(s):  
Hydrogen Bonding ◽  
Physical Properties ◽  
Intramolecular Hydrogen Bonding ◽  
Tautomeric Equilibrium ◽  
Phenolic Hydroxyl ◽  
Hydroxyl Group ◽  
Electronic Effects ◽  
Intramolecular Hydrogen

The preparation and physical properties of 27 compounds in the title series are described. Tautomerism, syn-anti isomerism, N.M.R. parameters, and the mechanism of isomerization are discussed. In this series of derivatives, the tautomeric equilibrium in dioxan solutions lies heavily towards the oxime form unless intramolecular hydrogen bonding between the substituent at C2 (or C6) and the phenolic hydroxyl group of the nitroso form is possible. The substituents at C2 (and C6) influence the position of the syn-anti equilibrium in the quinone monoxime forms through electronic effects.

13C CP/MAS NMR spectra of poly-β-D(1 → 4) mannose: mannan

1990 ◽  
Vol 68 (7) ◽  
pp. 1192-1195 ◽  
Author(s):  
R. H. Marchessault ◽  
M. G. Taylor ◽  
W. T. Winter
Keyword(s):  
Hydrogen Bonding ◽  
Solid State ◽  
Solid State Nmr ◽  
Nmr Spectra ◽  
Repeat Unit ◽  
Intramolecular Hydrogen Bonding ◽  
Lower Mobility ◽  
Intramolecular Hydrogen ◽  
Cp Mas Nmr ◽  
13C Cp Mas Nmr

13C solid-state NMR spectra (CP/MAS) were recorded for mannan polymorphs: mannan I ("ivory nut") and mannan II (Codiumfragile). These pure mannans, poly-β-(1 → 4) mannopyranose, show a single resonance for each carbon of the chemical repeat unit. This is the expected result based on the crystalline P212121 and 1222 symmetries. The T1 values were also recorded and the results are compared to those for cellulose obtained from the literature. The much lower mobility of C-6, even in noncrystalline mannan, compared to native cellulose is attributed to the epimeric difference at C-2 between cellulose and mannan allowing intramolecular hydrogen bonding in the former but not the latter. Keywords: mannan, solid state NMR, T1 relaxation, polysaccharide, ivory nut.

Structure of 5-Methyl-4-[(arylamino)methylene]-2,4-dihydro-3H-pyrazol-3-ones

1981 ◽  
Vol 34 (5) ◽  
pp. 1117 ◽  
Author(s):  
JE Rockley ◽  
LA Summers
Keyword(s):  
Hydrogen Bonding ◽  
Intramolecular Hydrogen Bonding ◽  
Tautomeric Forms ◽  
Intramolecular Hydrogen

5-Methyl-4-[(arylamino)methylene]-2,4-dihydro-3H-pyrazol-3-ones have been synthesized. Of the 12 possible tautomeric forms it has been shown that they exist as the (ary1amino)methylene tautomerwith intramolecular hydrogen bonding between the CO and exocyclic NH groups.

IR and NMR spectra, intramolecular hydrogen bonding and conformations of mercaptothiacalix[4]arene molecules and their para-tert-butyl-derivative

2007 ◽  
Vol 60 (3-4) ◽  
pp. 281-291 ◽  
Author(s):  
Sergey A. Katsyuba ◽  
Elena E. Zvereva ◽  
Alla V. Chernova ◽  
Artur R. Shagidullin ◽  
Svetlana E. Solovieva ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Nmr Spectra ◽  
Intramolecular Hydrogen Bonding ◽  
Ir And Nmr Spectra ◽  
Tert Butyl ◽  
Intramolecular Hydrogen
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