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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 32, Number 1
BKCSDE 32(1)
January 20, 2011 

 
Title
Kinetics and Mechanism of the Aminolysis of Aryl N-Benzyl Thiocarbamates in Acetonitrile
Author
Hyuck Keun Oh
Keywords
Nucleophilic substitution, Aryl N-benzyl thiocarbamates, Cross-interaction constant, Kinetic isotope effects, Concerted mechanism
Abstract
The aminolysis reactions of phenyl N-benzyl thiocarbamate with benzylamines in acetonitrile at 50.0 oC are investigated. The reactions are first order in both the amine and the substrate. Under amine excess, pseudo-first coefficient (kobs) are obtained, plot of kobs vs free amine concentration are linear. The signs of ρXZ (< 0) are consistent with concerted mechanism. Moreover, the variations of ρX and ρZ with respect to the sustituent in the substrate and large ρXZ value indicate that the reactions proceed concerted mechanism. The normal kinetic isotope effects (kH/kD = 1.3 ~ 1.5) involving deuterated benzylamine nucleophiles suggest a hydrogen-bonded, four-centered-type transition state. The activation parameters, ΔH and ΔS, are consistent with this transition state structure.
Page
137 - 140
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