Protonation of purines and related compounds in dimethylsulfoxide and water

1985 ◽  
Vol 63 (6) ◽  
pp. 1228-1232 ◽  
Author(s):  
Robert L. Benoit ◽  
Danielle Boulet ◽  
Luc Séguin ◽  
Monique Fréchette
Keyword(s):  
Solvent Effect ◽  
Functional Groups ◽  
Thermodynamic Data ◽  
Ionization Constants ◽  
Enthalpies Of Transfer ◽  
Heats Of Solution ◽  
Bonding Properties ◽  
Related Compounds

The ionization constants of the conjugated acids BH+ of purine, adenine, 9-methyladenine, adenosine, guanine, and hypoxanthine, and of the related compounds imidazole, N-methylimidazole, benzimidazole, and 4-amino-2,6-dimethylpyrimidine have been determined potentiometrically in Me2SO. The heats of solution and the heats of protonation of most of these bases have been obtained by calorimetry. Some additional determinations were carried out in water so that thermodynamic data in Me2SO and in water could be compared. Our discussion of the solvent effect on these data is largely based on a consideration of the enthalpies of transfer of B and BH+ and emphasizes the contrasting H-bonding properties of the solvents and of the functional groups on the solutes B and BH+.

Untersuchungen zum ternären System Bi/Te/O, III. Bestimmung thermodynamischer Daten der ternären Verbindungen/Investigations on the Ternary System Bi/Te/O,III. Determination of Thermodynamic Data of Ternary Compounds

1999 ◽  
Vol 54 (2) ◽  
pp. 252-260 ◽  
Author(s):  
P. Schmidt ◽  
C. Hennig ◽  
H. Oppermann
Keyword(s):  
Solid State ◽  
Ternary System ◽  
Thermodynamic Data ◽  
Phase Relations ◽  
Solid State Reactions ◽  
Enthalpies Of Formation ◽  
Ternary Compounds ◽  
Heats Of Solution

The phase relations in the ternary system Bi/Te/O have been determined in previous studies by solid state reactions. Thermodynamical data have now been obtained for the pertinent equilibria. The heats of solution of Bi2O3, Bi12TeO20, Bi10Te2O19, Bi16Te5O34, Bi2TeO5, Bi2Te2O7, Bi2Te4O11 and TeCl4 were determined in 4N HCl. From these the enthalpies of formation of bismuth tellurites at 298 K have been derived:⊿H°b (Bi12TeO20, f, 298) = -901,6 ± 8 kcal/mol,⊿H°b (Bi10Te2O19, f, 298) = -856,1 ± 9 kcal/mol,⊿H°b (Bi16Te5O34, f, 298) = -1519,5 ± 17 kcal/mol,⊿H°b (Bi2TeO5, f, 298)= -222,8 ± 3 kcal/mol,⊿H°b (Bi2Te2O7, f, 298)= -299,4 ± 4 kcal/mol,⊿H°b (Bi2Te4O11, f, 298)= -448,2 ± 7 kcal/mol.

scholarly journals Facile Deoxygenation of Hydroxylated Flavonoids by Palladium-Catalysed Reduction of its Triflate Derivatives

2005 ◽  
Vol 60 (7) ◽  
pp. 792-796 ◽  
Author(s):  
József Kövér ◽  
Sándor Antus
Keyword(s):  
Formic Acid ◽  
Functional Groups ◽  
Catalytic Amount ◽  
Palladium Acetate ◽  
Efficient Procedure ◽  
Related Compounds

An efficient procedure to deoxygenate hydroxy substituted flavonoids, isoflavonoids and related compounds via their trifluoromethanesulfonates is presented. Their reduction with formic acid in the presence of a catalytic amount of palladium acetate, triethylamine and 1,3-bis(diphenylphosphanyl) propane (dppp) in DMF results in their des-hydroxy derivatives without affecting other functional groups.

Solvent effect on the proton-transfer equilibria and thermodynamic data of the hydrogen bond in a Mannich base

1984 ◽  
Vol 88 (2) ◽  
pp. 321-323 ◽  
Author(s):  
Maria Rospenk ◽  
Johannes Fritsch ◽  
Georg Zundel
Keyword(s):  
Hydrogen Bond ◽  
Proton Transfer ◽  
Solvent Effect ◽  
Thermodynamic Data ◽  
Mannich Base

Solvent Effect on Functional Groups Attached to Edges of Carbon Nanotubes

Nano Letters ◽  
2002 ◽  
Vol 2 (6) ◽  
pp. 573-575 ◽  
Author(s):  
T. Halicioglu ◽  
R. L. Jaffe
Keyword(s):  
Carbon Nanotubes ◽  
Solvent Effect ◽  
Functional Groups

The Fine Structure of Cytosine

1962 ◽  
Vol 15 (4) ◽  
pp. 851 ◽  
Author(s):  
DJ Brown ◽  
M Lyall
Keyword(s):  
Aqueous Solution ◽  
Nuclear Magnetic Resonance ◽  
Fine Structure ◽  
Magnetic Resonance ◽  
Nuclear Magnetic Resonance Spectrum ◽  
Tautomeric Form ◽  
Resonance Spectrum ◽  
Ionization Constants ◽  
Recent Formulation ◽  
Related Compounds

The ionization constants and ultraviolet spectra of cytosine, of its appropriately methylated derivatives, and of related compounds are used to indicate that its pre- dominant tautomeric form in aqueous solution is 4-amino-1,2-dihydro-2-oxopyrimidine. This is in sharp contrast to its recent formulation as a zwitterion on the grounds of its nuclear magnetic resonance spectrum.

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