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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 33, Number 2
BKCSDE 33(2)
February 20, 2012 

Kinetics and Mechanism of the Anilinolysis of Dibutyl Chlorophosphate in Acetonitrile
Md. Ehtesham Ul Hoque, Hai Whang Lee *
Phosphoryl transfer reaction, Anilinolysis, Dibutyl chlorophosphate, Deuterium kinetic isotope effect
The nucleophilic substitution reactions of dibutyl chlorophosphate (3) with substituted anilines (XC6H4NH2) and deuterated anilines (XC6H4ND2) are investigated kinetically in acetonitrile at 55.0 oC. The obtained deuterium kinetic isotope effects (DKIEs; kH/kD) are secondary inverse (kH/kD = 0.86-0.97) with the strongly basic anilines while primary normal (kH/kD = 1.04-1.10) with the weakly basic anilines. The DKIEs, steric effects of the two ligands, activation parameters, cross-interaction constants, variation trends of the kH/kD values with X, and mechanism are discussed for the anilinolyses of the nine (R1O)(R2O)P(=O)Cl-type chlorophosphates. A concerted mechanism is proposed with a backside nucleophilic attack transition state for the strongly basic anilines and with a frontside attack involving a hydrogen-bonded four-center-type transition state for the weakly basic anilines on the basis of the magnitudes, secondary inverse and primary normal, and variation trends of the kH/kD values with X.
663 - 669
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