Kinetic isotope effects and aliphatic diazo-compounds. Part I. General acid catalysis and the Brønsted coefficients

1972 ◽  
pp. 2180-2185 ◽  
Author(s):  
W. J. Albery ◽  
A. N. Campbell-Crawford ◽  
K. S. Hobbs
Keyword(s):  
Acid Catalysis ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Diazo Compounds ◽  
Kinetic Isotope ◽  
General Acid

Vinyl ether hydrolysis. XIII. The failure of I-strain to produce a change in rate-determining step

1980 ◽  
Vol 58 (2) ◽  
pp. 124-129 ◽  
Author(s):  
Y. Chiang ◽  
W. K. Chwang ◽  
A. J. Kresge ◽  
S. Szilagyi
Keyword(s):  
Vinyl Ether ◽  
Acid Catalysis ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Mineral Acid ◽  
Buffer Solutions ◽  
Rate Determining Step ◽  
Kinetic Isotope ◽  
Acetic Acid Buffer ◽  
Hydrolysis Of

Rates of hydrolysis of 1-ethoxy-3,3,5,5-tetramethylcyclopentene and 1-methoxy-2,3,3,5,5-pentamethylcyclopentene measured in mineral acid and formic and acetic acid buffer solutions show general acid catalysis and give large kinetic isotope effects in the normal direction (kH/kD > 1). This indicates that these reactions proceed by the conventional mechanism for vinyl ether hydrolysis in which proton transfer from the catalyzing acid to the substrate is rate-determining, and that the I-strain in these substrates is insufficiently great to shift the reaction mechanism to rapidly reversible substrate protonation followed by rate-determining hydration of the ensuing cationic intermediate.

Some Kinetic and Equilibrium Isotope Effects in the Isobutylphenone Eno land Enolate Ion System

1989 ◽  
Vol 44 (5) ◽  
pp. 406-412 ◽  
Author(s):  
Y. Chiang ◽  
A. J. Kresge ◽  
P. A. Walsh
Keyword(s):  
Acetic Acid ◽  
Isotope Effect ◽  
Acid Catalysis ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Free Energies ◽  
Kinetic Isotope ◽  
Hydronium Ion ◽  
Acid Catalyzed ◽  
Water Catalysis

The following kinetic isotope effects were determined for acid-catalyzed ketonization of isobutyrophenone enol and enolate ion through rate-determining hydron transfer from catalyst to substrate: enol, kH/kD = 3.30±0.07 (hydronium ion catalysis), kH/kD = 4.0 + 2.8 (acetic acid catalysis); enolate ion, kH/kD= 1.00 + 0.21 (hydronium ion catalysis), kH/kD = 3A \ +0.20 (acetic acid catalysis), kH/kD = 7.48±0.23 (water catalysis). The magnitude of these isotope effects, when assessed in terms of the free energies of reaction for the processes in which they occur, are consistent with Melander-Westheimer- Bigeleisen theory. An equilibrium isotope effect of KH/KD = 5.88±0.32 was also determined for the ionization of isobutyrophenone enol as an oxygen acid.

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