Kinetics and mechanism of the aminolysis of aryl phenyl chlorothiophosphates with anilines.
Kinetic studies of the reactions of aryl phenyl chlorothiophosphates (1) and aryl 4-chlorophenyl chlorothiophosphates (2) with substituted anilines in acetonitrile at 55.0 degrees C are reported. The negative values of the cross-interaction constant rhoXY (rhoXY = -0.22 and -0.50 for 1 and 2, respectively) between substituents in the nucleophile (X) and substrate (Y) indicate that the reactions proceed by concerted SN2 mechanism. The primary kinetic isotope effects (kH/kD = 1.11-1.13 and 1.10-1.46 for 1 and 2, respectively) involving deuterated aniline nucleophiles are obtained. Front- and back-side nucleophilic attack on the substrates is proposed mainly on the basis of the primary kinetic isotope effects. A hydrogen-bonded, four-center-type transition state is suggested for a front-side attack, while the trigonal bipyramidal pentacoordinate transition state is suggested for a back-side attack. The MO theoretical calculations of the model reactions of dimethyl chlorothiophosphate (1') and dimethyl chlorophosphate (3') with ammonia are carried out. Considering the specific solvation effect, the front-side nucleophilic attack can occur competitively with the back-side attack in the reaction of 1'.
Hoque
Md Ehtesham Ul
ME
Department of Chemistry, Inha University, Incheon 402-751, Korea.
Dey
Shuchismita
S
Guha
Arun Kanti
AK
Kim
Chan Kyung
CK
Lee
Bon-Su
BS
Lee
Hai Whang
HW
D000588:Amines / Q000737:chemistry*; D000814:Aniline Compounds / Q000737:chemistry*; D007700:Kinetics; D008958:Models, Molecular; D010710:Phosphates / Q000737:chemistry*
D000588:Amines; D000814:Aniline Compounds; D010710:Phosphates; C023650:aniline; C035638:thiophosphoric acid