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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 33, Number 10
BKCSDE 33(10)
October 20, 2012 

 
Title
Kinetics and Mechanism of the Pyridinolysis of Diisopropyl Chlorothiophosphate in Acetonitrile
Author
Md. Ehtesham Ul Hoque, Hai Whang Lee*
Keywords
Thiophosphoryl transfer reaction, Diisopropyl chlorothiophosphate, Pyridinolysis, Biphasic concave upward free energy relationship
Abstract
The nucleophilic substitution reactions of diisopropyl chlorothiophosphate (5) with X-pyridines have been kinetically studied in MeCN at 35.0 oC. The Hammett and Brönsted plots for the substituent X variations in the nucleophiles show biphasic concave upwards with a break point at X = 3-Ph. The pyridinolysis rate of 5 exhibits great negative deviation from the Taft plot. A concerted SN2 mechanism is proposed involving a change of the attacking direction of the X-pyridines from a frontside attack with the strongly basic pyridines to a backside attack with the weakly basic pyridines.
Page
3203 - 3207
Full Text
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