Secondary Kinetic Isotope Effect in Nucleophilic Substitution:  A Quantum-Mechanical Approach†

2006 ◽  
Vol 110 (9) ◽  
pp. 3071-3079 ◽  
Author(s):  
Carsten Hennig ◽  
Rainer B. Oswald ◽  
Stefan Schmatz
Keyword(s):  
Nucleophilic Substitution ◽  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Quantum Mechanical ◽  
Kinetic Isotope ◽  
Mechanical Approach ◽  
Quantum Mechanical Approach

Quantum Mechanical Tunneling in Homodienyl Sigmatropic [1,5]-Hydrogen Shifts of (Hydroxymethyl)styrylcyclopropanes

1990 ◽  
Vol 43 (6) ◽  
pp. 1071 ◽  
Author(s):  
GG Pegg ◽  
GV Meehan
Keyword(s):  
Low Temperature ◽  
Temperature Dependence ◽  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Natural Compounds ◽  
Quantum Mechanical ◽  
Strong Temperature Dependence ◽  
Quantum Mechanical Tunneling ◽  
Hydrogen Migration ◽  
Kinetic Isotope

The strong temperature dependence of the deuterium kinetic isotope effect observed for homodienyl [1,5]-hydrogen migration of [hydroxy (D)methyl] styrylcyclopropanes (1c,d) in hexane solvent is suggestive of a significant tunnelling contribution to the mechanism. While the hydroxy substituent at the migration origin appears to influence the thermolytic behaviour of these molecules, attempts to promote oxy anionic homodienyl rearrangement in the isotopically natural compounds (1a,b) at low temperature were unsuccessful.

Isotope effects in nucleophilic substitution reactions. II. Secondary α-deuterium kinetic isotope effects: a criterion of mechanism?

1979 ◽  
Vol 57 (9) ◽  
pp. 1089-1097 ◽  
Author(s):  
Kenneth Charles Westaway ◽  
Syed Fasahat Ali
Keyword(s):  
Transition State ◽  
Nucleophilic Substitution ◽  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Substitution Reactions ◽  
Nucleophilic Substitution Reactions ◽  
Kinetic Isotope ◽  
Steric Crowding

A very large secondary α-deuterium kinetic isotope effect of 1.179 ± 0.007 (1.086 ± 0.003 per α-deuterium) has been observed for the SN2 reaction of thiophenoxide ion with benzyldimethylphenylammonium ion in DMF at 0°C. This large isotope effect which is far outside the range reported for SN2 reactions, is attributed to the fact that the extraordinarily large steric crowding around the Cα—H bonds in the substrate is reduced in the SN2 transition state. The structure of the transition state is shown to be consistent with this hypothesis.

Isotope effects in nucleophilic substitution reactions X. The effect of changing the nucleophilic atom on ion-pairing in an SN2 reaction

1998 ◽  
Vol 76 (6) ◽  
pp. 758-764 ◽  
Author(s):  
Yao-ren Fang ◽  
Zhu-gen Lai ◽  
Kenneth Charles Westaway
Keyword(s):  
Transition State ◽  
Nucleophilic Substitution ◽  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Isotope Effects ◽  
Substituent Effects ◽  
Ion Pairing ◽  
State Structure ◽  
Transition State Structure ◽  
Kinetic Isotope

The effect of ion-pairing in an SN2 reaction is very different when the nucleophilic atom is changed from sulfur to oxygen, i.e., changing the nucleophile from thiophenoxide ion to phenoxide ion. When the nucleophile is sodium thiophenoxide, ion-pairing markedly alters the secondary α -deuterium kinetic isotope effect (transition state structure) and the substituent effect found by changing the para substituent on the nucleophile. When the nucleophile is sodium phenoxide, ion-pairing does not significantly affect the secondary α -deuterium or the chlorine leaving group kinetic isotope effects (transition state structure) or the substituent effects found by changing a para substituent on the nucleophile or the substrate. The different effects of ion-pairing may occur because the electron density on the hard oxygen atom of the sodium phenoxide is not affected significantly by ion-pairing.Key words: nucleophilic substitution, SN2, kinetic isotope effect, transition state, substituent effects, ion-pair.

Quantum electrocatalysts: theoretical picture, electrochemical kinetic isotope effect analysis, and conjecture to understand microscopic mechanisms

2020 ◽  
Vol 22 (20) ◽  
pp. 11219-11243 ◽  
Author(s):  
Ken Sakaushi
Keyword(s):  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Effect Analysis ◽  
Kinetic Isotope

The fundamental aspects of quantum electrocatalysts are discussed together with the newly developed electrochemical kinetic isotope effect (EC-KIE) approach.

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