RELATIVE HYDROGEN BONDING OF DEUTERIUM. II. ACID IONIZATION CONSTANTS IN H2O AND D2O1

1962 ◽  
Vol 66 (3) ◽  
pp. 429-433 ◽  
Author(s):  
A. O. McDougall ◽  
F. A. Long
Keyword(s):  
Hydrogen Bonding ◽  
Ionization Constants ◽  
Acid Ionization ◽  
Acid Ionization Constants

Carboxylic acid amide enols: keto-enol/enolate interconversion of N-methylindoline-2-one and its 2-thione and 2-selone analogs in aqueous solution

1999 ◽  
Vol 77 (9) ◽  
pp. 1528-1536 ◽  
Author(s):  
A Jerry Kresge ◽  
Qingshui Meng
Keyword(s):  
Aqueous Solution ◽  
Isotope Effects ◽  
Acid Amide ◽  
Spectrophotometric Titration ◽  
Base Catalysis ◽  
Ionization Constants ◽  
Acidity Constant ◽  
Carbon Acid ◽  
Acid Ionization ◽  
Acid Ionization Constants

Carbon-acid ionization constants, QaK (concentration quotient at ionic strength = 0.10 M), were determined by spectrophotometric titration in aqueous solution for N-methylindoline-2-one, pQaK = 15.70, N-methylindoline-2-thione, pQaK = 8.93, and N-methylindoline-2-selone, pQaK = 7.25. Rate profiles were also constructed for the thione and selone. These were interpreted, with support from the form of acid-base catalysis as well as solvent and substrate isotope effects, as representing keto - enol/enolate ion interconversion. That led to the enol acidity constant pQaE = 4.05 and the keto-enol equilibrium constant pKE = 4.88 for the thione and estimates of the limits on these quantities, pQaE< 3 and pKE > 4, for the selone.Key words: lactam, thiolactam, selenolactam, keto-enol equilibria, carbon-acid ionization constants.

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