Kinetic hydrogen isotope effects in a proton-transfer reaction: the general acid-catalyzed hydrolysis of cyanoketen dimethylacetal

1967 ◽  
pp. 40
Author(s):  
V. Gold ◽  
D. C. A. Waterman
Keyword(s):  
Proton Transfer ◽  
Hydrogen Isotope ◽  
Transfer Reaction ◽  
Isotope Effects ◽  
Proton Transfer Reaction ◽  
General Acid ◽  
Acid Catalyzed ◽  
Hydrolysis Of

Crystallization kinetics of cerium oxide nanoparticles formed by spontaneous, room-temperature hydrolysis of cerium(iv) ammonium nitrate in light and heavy water

2017 ◽  
Vol 19 (5) ◽  
pp. 3523-3531 ◽  
Author(s):  
Natasha W. Pettinger ◽  
Robert E. A. Williams ◽  
Jinquan Chen ◽  
Bern Kohler
Keyword(s):  
Proton Transfer ◽  
Heavy Water ◽  
Room Temperature ◽  
Transfer Reaction ◽  
Proton Transfer Reaction ◽  
Cerium Oxide Nanoparticles ◽  
Oxide Nanoparticles ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Cerium Iv Ammonium Nitrate

Ceria nanocrystals form tenfold more slowly in D2O vs. H2O, revealing a rate-determining proton transfer reaction and a non-classical crystallization mechanism.

Kinetic study of the proton transfer reaction between 1-nitro-1-(4-nitrophenyl)alkanes and TBD and MTBD bases in acetonitrile solvent

2001 ◽  
Vol 79 (7) ◽  
pp. 1128-1134 ◽  
Author(s):  
Iwona Grzeskowiak ◽  
Wtodzimierz Galezowski ◽  
Arnold Jarczewski
Keyword(s):  
Proton Transfer ◽  
Kinetic Study ◽  
Transfer Reaction ◽  
Isotope Effects ◽  
Ion Pairs ◽  
Kinetic Isotope Effects ◽  
Proton Transfer Reaction ◽  
Comparable Amount ◽  
Kinetic Isotope ◽  
Proton Transfer Reactions

The rates of proton transfer reactions between C-acids of the series of nitroalkanes with increasing bulk of R = H, Me, Et, i-Pr substituent as: 4-nitrophenylnitromethane (0), 1-(4-nitrophenyl)-1-nitroethane (1), 1-(4-nitrophenyl)-1-nitropropane (2), 2-methyl-1-(4-nitrophenyl)-1-nitropropane (3) and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD) have been measured in acetonitrile at pseudo-first-order conditions. The product of the proton transfer reaction with MTBD in acetonitrile is dissociated into free ions while that of the TBD reaction is composed of a comparable amount of ions and ion pairs. The second-order rate constants (k2H) for these bases of almost equal strength in acetonitrile (pKa = 24.70, 24.97 for MTBD and TBD) and C-acids 1, 2, and 3 are: 317, 86, 7.6 dm3 mol–1 s–1; and 15 200, 5300, 1100 dm3 mol–1 s–1, respectively. The appropriate primary deuterium kinetic isotope effects (kH/kD) are 12.5, 10.8, 6.9; and 9.9, 11.2, 12.6. The influence of steric hindrance brought by reacting C-acids and bases is discussed. The different structure of the transition states and the products as mono- and double-hydrogen bonded complexes for these series of C-acids and MTBD and TBD bases is manifested by a distinct reaction mechanism which we attempt to explain.Key words: proton transfer, kinetic study, C-acids, organic bases, acetonitrile, kinetic isotope effects.

Phenyltetramethylguanidines: substituent effect on rates and isotope effects in their reaction with bis(4-nitrophenyl)cyanomethane in acetonitrile

1991 ◽  
Vol 69 (2) ◽  
pp. 205-210 ◽  
Author(s):  
Przemyslaw Pruszynski ◽  
Kenneth T. Leffek
Keyword(s):  
Proton Transfer ◽  
Transfer Reaction ◽  
Isotope Effects ◽  
Proton Transfer Reaction ◽  
Kinetic Isotope ◽  
Reaction Constant ◽  
Base Strength ◽  
Derivatives Of ◽  
Best Fit ◽  
Hammett Relationship

A series of 22 phenyl substituted derivatives of 2-phenyl-1,1′,3,3′-tetramethylguanidine were used as bases in the proton transfer reaction from bis(4-nitrophenyl)cyanomethane in acetonitrile solvent. Brønsted and Hammett type relationships are examined for this family of closely related substrates. The Brønsted relationship constructed from the pKa values determined in acetonitrile shows β = 0.55 ± 0.03. The best fit of the Hammett relationship, with special values for p-NO2 and p-CN groups, gives the reaction constant ρ = −1.39 ± 0.1. The kinetic isotope effect, kH/kD, increases from 9.6 to 12.4 at 25 °C with decreasing base strength, i.e., when the reaction becomes more thermoneutral. Key words: tetramethylguanidine, proton transfer, deuterium isotope effects.

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