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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 32, Number 9
BKCSDE 32(9)
September 20, 2011 

 
Title
Kinetics and Mechanism of the Anilinolysis of 1,2-Phenylene Phosphorochloridate in Acetonitrile
Author
Hasi Rani Barai, Hai Whang Lee *
Keywords
Phosphoryl transfer reaction, Anilinolysis, 1,2-Phenylene phosphorochloridate, Biphasic concave upward free energy correlation, Deuterium kinetic isotope effect
Abstract
The nucleophilic substitution reactions of 1,2-phenylene phosphorochloridate (1) with substituted anilines (XC6H4NH2) and deuterated anilines (XC6H4ND2) are investigated kinetically in acetonitrile at –15.0 oC. The studied substrate of 1,2-phenylene phosphorochloridate is cyclic five-membered ring of phosphorus ester, and the anilinolysis rate of 1 is much faster than its acyclic analogue (4: ethyl phenyl chlorophosphate) because of extremely small magnitude of the entropy of activation of 1 compared to 4. The Hammett and Brönsted plots exhibit biphasic concave upwards for substituent X variations in the nucleophiles with a break point at X = 3- Me. The values of deuterium kinetic isotope effects (DKIEs; kH/kD) change from secondary inverse (kH/kD < 1) with the strongly basic anilines to primary normal (kH/kD > 1) with the weakly basic anilines. The secondary inverse with the strongly basic anilines and primary normal DKIEs with the weakly basic anilines are rationalized by the transition state (TS) variation from a predominant backside attack to a predominant frontside attack, in which the reaction mechanism is a concerted SN2 pathway. The primary normal DKIEs are substantiated by a hydrogen bonded, four-center-type TS.
Page
3355 - 3360
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