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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 35, Number 4
BKCSDE 35(4)
April 20, 2014 

 
Title
Nucleophilic Substitution Reactions of O-Methyl N,N-Diisopropylamino Phosphonochloridothioate with Anilines and Pyridines
Author
Hasi Rani Barai, Hai Whang Lee*
Keywords
Thiophosphoryl transfer reaction, Anilinolysis, Pyridinolysis, O-Methyl N,N-diisopropylamino phosphonochloridothioate, Biphasic concave upward free energy relationship
Abstract
The kinetic studies on the reactions of O-methyl N,N-diisopropylamino phosphonochloridothioate with Xanilines and X-pyridines have been carried out in acetonitrile. The free energy relationship with X in the anilines exhibits biphasic concave upwards with a break region between X = (H and 4-F), giving unusual negative βX and positive ρX values with weakly basic anilines. The unusual phenomenon is rationalized by isokinetic relationship. A stepwise mechanism with a rate-limiting leaving group departure from the intermediate is proposed based on the selectivity parameter and variation trend of the deuterium kinetic isotope effects with X. The free energy relationship with X in the pyridines exhibits biphasic concave upwards with a break point at X = 3-MeO. A concerted mechanism is proposed based on relatively small βX value, and frontside and backside nucleophilic attack are proposed with strongly and weakly basic pyridines, respectively.
Page
1016 - 1022
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