Determination of the Chlorine Kinetic Isotope Effect on the 4-Chlorobenzoyl-CoA Dehalogenase-Catalyzed Nucleophilic Aromatic Substitution

2002 ◽  
Vol 398 (2) ◽  
pp. 249-252 ◽  
Author(s):  
Andrzej Lewandowicz ◽  
Juliusz Rudzinski ◽  
Lusong Luo ◽  
Debra Dunaway-Mariano ◽  
Piotr Paneth
Keyword(s):  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Nucleophilic Aromatic Substitution ◽  
Aromatic Substitution ◽  
Kinetic Isotope ◽  
Chlorobenzoyl Coa Dehalogenase

Method of determination of the kinetic isotope effect in a mixture of reacting isotopomers

2012 ◽  
Vol 48 (3) ◽  
pp. 157-162 ◽  
Author(s):  
R. S. Mitchenko ◽  
T. V. Krasnyakova ◽  
I. V. Zhikharev ◽  
S. A. Mitchenko
Keyword(s):  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Kinetic Isotope ◽  
Method Of Determination

The Determination of the Preferred Stereochemistry and the Magnitude of the Hydrogen Isotope Effect for 1,3 Elimination in the Locked Norbornyl System Methyl exo-2-Bromo-1-norbornanecarboxylate-endo, endo-5,6-d2

1975 ◽  
Vol 53 (1) ◽  
pp. 26-40 ◽  
Author(s):  
Nick Henry Werstiuk
Keyword(s):  
Isotope Effect ◽  
Hydrogen Isotope ◽  
Kinetic Isotope Effect ◽  
Front Face ◽  
Elimination Kinetic ◽  
Kinetic Isotope ◽  
Hydrogen Isotope Effect

Methyl exo-2-bromo-1-norobornanecarboxylate-endo,endo-5,6-d2 (1b) has been prepared and solvolyzed at 112° in 80:20 EtOH-H2O buffered with NaOAc. The loss of 85–90% of the deuterium available on the front face of 1b in the formation of the tricyclic ester 6D coupled with a novel analysis established that the endo:exo preference for 1,3 elimination is at least 15:1 to 20:1. A comparison of the solvolytic kinetic isotope effect (1.18 ± 0.04) for 1b and the 1,3-elimination kinetic isotope effect (1.45–1.6) with data for 1,2 eliminations indicates that elimination occurs from the classical, perhaps 1,3 hyperconjugatively stabilized carbocation 20. The endo:exo preference established in this study is used to reinterpret 1,3-elimination data determined by Collins in the solvolysis of deuteriohydroxyphenyl norbornyl tosylates.

The base-catalysed anomerization of dinitrophenyl glycosides: evidence for a novel reaction mechanism

1990 ◽  
Vol 68 (10) ◽  
pp. 1859-1866 ◽  
Author(s):  
Leise A. Berven ◽  
David Dolphin ◽  
Stephen G. Withers
Keyword(s):  
Reaction Mechanism ◽  
Reaction Rate ◽  
Kinetic Isotope Effect ◽  
Substituent Effects ◽  
Proton Exchange ◽  
Nucleophilic Aromatic Substitution ◽  
Aromatic Substitution ◽  
Proton Abstraction ◽  
Sugar Moiety ◽  
Kinetic Isotope

The mechanism of base-catalysed anomerization of per-O-acetylated 2,4-dinitrophenyl-β-D-glucopyranoside in dimethylsulfoxide has been investigated using a variety of techniques. A mechanism involving proton abstraction at C-1 was eliminated by the absence of proton exchange at that center and the measurement of a secondary deuterium kinetic isotope effect for the 1-deuterio substrate. A mechanism involving phenolate departure and recombination is rendered unlikely on the basis of remote substituent effects on the reaction rate and by the absence of any exchange of the phenyl moiety with added phenolate. A mechanism involving nucleophilic aromatic substitution initiated by an attack of the dimethylsulfinyl anion to generate a glucosyl oxyanion intermediate that anomerizes and recombines with the reactive aryl intermediate is consistent with the observations. This mechanism is further supported by the observation of a purple Meisenheimer complex intermediate and by the observed exchange between the substrate containing a labelled sugar moiety and added unlabelled 2,3,4,6-tetra-O-acetyl-β-D-glucopyranose. Keywords: glycoside, anomerization, reaction mechanism.

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