Kinetic isotope effects for gas phase SN2 methyl transfer: a computational study of anionic and cationic identity reactions

2002 ◽  
pp. 591-597 ◽  
Author(s):  
Giuseppe D. Ruggiero ◽  
Ian H. Williams
Keyword(s):  
Gas Phase ◽  
Computational Study ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Kinetic Isotope ◽  
Methyl Transfer

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.

Measurements of Solvent and Secondary Kinetic Isotope Effects for the Gas-Phase SN2 Reactions of Fluoride with Methyl Halides

1994 ◽  
Vol 116 (8) ◽  
pp. 3609-3610 ◽  
Author(s):  
Richard A. J. O'Hair ◽  
Gustavo E. Davico ◽  
Jale Hacaloglu ◽  
Thuy Thanh Dang ◽  
Charles H. DePuy ◽  
...  
Keyword(s):  
Gas Phase ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Methyl Halides ◽  
Sn2 Reactions ◽  
Kinetic Isotope

scholarly journals Deuterium kinetic isotope effects in microsolvated gas-phase E2 reactions

2007 ◽  
Vol 18 (6) ◽  
pp. 1046-1051 ◽  
Author(s):  
Nicole Eyet ◽  
Stephanie M. Villano ◽  
Shuji Kato ◽  
Veronica M. Bierbaum
Keyword(s):  
Gas Phase ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Kinetic Isotope

Activation of methane by gaseous platinum(II) ions PtX+ (X = H, Cl, Br, CHO)

2005 ◽  
Vol 83 (11) ◽  
pp. 1936-1940 ◽  
Author(s):  
Detlef Schröder ◽  
Helmut Schwarz
Keyword(s):  
Mass Spectrometry ◽  
Key Words ◽  
Electrospray Ionization ◽  
Gas Phase ◽  
Bond Activation ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Methane Activation ◽  
Gas Phase Reactions ◽  
Kinetic Isotope

The gas-phase reactions of methane with the platinum(II) ions PtX+ with X = H, Cl, Br, and CHO are studied by mass spectrometry. The PtX+ ions are generated by electrospray ionization of methanolic solutions of hexachloroplatinic acid and hexabromoplatinic acid, respectively. Small to moderate intramolecular kinetic isotope effects determined for the C—H(D) bond activation of CH2D2 suggest that the activation of methane by gaseous PtX+ cations is subject to thermochemical control by the product channels. In addition, the PtCl2+ cation is also able to activate methane, whereas PtCl3+ is unreactive under the conditions chosen. Key words: gas-phase reactions, mass spectrometry, methane activation, platinum bromide, platinum chloride.

Deuterium kinetic isotope effects on the thermal isomerizations of deuteriocyclopropane to deuterium-labeled propenes

2005 ◽  
Vol 83 (9) ◽  
pp. 1510-1515
Author(s):  
John E Baldwin ◽  
Stephanie R Singer
Keyword(s):  
Key Words ◽  
Gas Phase ◽  
Bond Cleavage ◽  
Isotope Effects ◽  
Reactive Intermediates ◽  
Kinetic Isotope Effects ◽  
Thermal Rearrangement ◽  
Carbon Bond ◽  
Kinetic Isotope ◽  
Carbon Carbon Bond

The gas-phase thermal isomerizations of deuteriocyclopropane to the four possible monodeuterium-labeled propenes have been followed at 435 °C. The observed distribution of products provides estimates of two deuterium kinetic isotope effects, the secondary [Formula: see text] for the carbon–carbon bond cleavage leading to trimethylene diradical reactive intermediates and the primary [Formula: see text] ratio for a [1,2] shift of a hydrogen or deuterium leading from the diradical to a labeled propene. The values determined are [Formula: see text] = 1.09 ± 0.03 and [Formula: see text] = 1.55 ± 0.06. The experimental [Formula: see text] value found agrees well with some, but not all, earlier calculated values and conjectures. Key words: cyclopropane, thermal rearrangement, kinetic isotope effects.

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