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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 35, Number 5
BKCSDE 35(5)
May 20, 2014 

 
Title
Kinetics and Mechanism of Pyridinolysis of O,O-Diethyl S-Aryl Phosphorothioates
Author
Hasi Rani Barai, Hai Whang Lee*
Keywords
Biphasic concave upward free energy correlation, Phosphoryl transfer reaction, Pyridinolysis, O,O-Diethyl S-aryl phosphorothioates, Cross-interaction constant
Abstract
The kinetic studies on the reactions of O,O-diethyl Z-S-aryl phosphorothioates with X-pyridines have been carried out in dimethyl sulfoxide. The free energy correlations with X in the nucleophiles are biphasic concave upwards with a break point at X = H, while those for substituent Z variations in the leaving groups are linear. The negative sign of ρXZ implies that the reaction proceeds through a concerted mechanism for both the strongly and weakly basic pyridines. The biphasic concave upward free energy relationships with X are rationalized by a change in the nucleophilic attacking direction from frontside with the strongly basic pyridines to backside with the weakly basic pyridines.
Page
1329 - 1332
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