QM/MM Determination of Kinetic Isotope Effects for COMT-Catalyzed Methyl Transfer Does Not Support Compression Hypothesis

2004 ◽  
Vol 126 (28) ◽  
pp. 8634-8635 ◽  
Author(s):  
Giuseppe D. Ruggiero ◽  
Ian H. Williams ◽  
Maite Roca ◽  
Vicent Moliner ◽  
Iñaki Tuñón
Keyword(s):  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Kinetic Isotope ◽  
Methyl Transfer

ChemInform Abstract: PULSE RADIOLYTIC DETERMINATION OF KINETIC ISOTOPE EFFECTS OF THE ADDITION REACTION OF HYDROGEN ATOMS TO ETHYLENE AND PROPENE

1976 ◽  
Vol 7 (12) ◽  
pp. no-no
Author(s):  
D. MIHELCIC ◽  
V. SCHUBERT ◽  
F. HOEFLER ◽  
P. POTZINGER
Keyword(s):  
Addition Reaction ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Hydrogen Atoms ◽  
Kinetic Isotope

Theoretical simulation of Brønsted correlations for proton transfer and methyl transfer: the significance of the Brønsted coefficient β

1999 ◽  
Vol 77 (5-6) ◽  
pp. 830-841 ◽  
Author(s):  
Ian H Williams ◽  
Paul A Austin
Keyword(s):  
Proton Transfer ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Molecular Orbital Calculations ◽  
Theoretical Simulation ◽  
Kinetic Isotope ◽  
Methyl Transfer ◽  
Equilibrium Relationship ◽  
Substituted Pyridines ◽  
Very High

Brønsted correlations for proton transfer and methyl transfer between pairs of mimicked 4-substituted pyridines have been simulated by means of AM1 molecular orbital calculations. The enthalpies of activation and of reaction are well correlated by the Marcus relation. The Brønsted correlation is markedly curved for proton transfer for which the Marcus intrinsic barrier is very low (~ 5 kJ mol-1). Conversely, the Brønsted correlation is almost imperceptibly curved for methyl transfer for which the Marcus intrinsic barrier is very high (~ 152 kJ mol-1). The slope of the Brønsted correlation provides an approximate measure of the position of the transition structure along the reaction coordinate between the reactant and product encounter complexes. Primary kinetic isotope effects for proton transfer show a broad maximum, centered on ΔHrxn = 0, when plotted against reaction exo/endothermicity only if computed with respect to isolated acids and bases, but intracomplex kinetic isotope effects show a maximum displaced significantly towards the endothermic proton transfers.Key words: Brønsted correlation, rate-equilibrium relationship, transition state, isotope effect.

Evidence for a rate-determining solvation change in methyl transfer to water. Solvent dependence of water-deuterium oxide kinetic isotope effects

1986 ◽  
Vol 108 (11) ◽  
pp. 2960-2968 ◽  
Author(s):  
Joseph L. Kurz ◽  
Jasun. Lee ◽  
Mark E. Love ◽  
Susan. Rhodes
Keyword(s):  
Deuterium Oxide ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Water Solvent ◽  
Kinetic Isotope ◽  
Methyl Transfer ◽  
Solvent Dependence

Influence of Compression upon Kinetic Isotope Effects for SN2 Methyl Transfer:  A Computational Reappraisal

2000 ◽  
Vol 122 (44) ◽  
pp. 10895-10902 ◽  
Author(s):  
Vicent Moliner ◽  
Ian H. Williams
Keyword(s):  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Kinetic Isotope ◽  
Methyl Transfer
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