Kinetics and mechanism of the aminolysis of aryl ethyl chloro and chlorothio phosphates with anilines.
The reactions of ethyl Y-phenyl chloro (1) and chlorothio (2) phosphates with X-anilines in acetonitrile at 55.0 degrees C are studied kinetically and theoretically. Kinetic results yield the primary kinetic isotope effects (k(H)/k(D) = 1.07-1.80 and 1.06-1.27 for 1 and 2, respectively) with deuterated aniline (XC(6)H(4)ND(2)) nucleophiles, and the cross-interaction constants rho(XY) = -0.60 and -0.28 for and , respectively. A concerted mechanism involving a partial frontside attack through a hydrogen-bonded, four-center-type transition state is proposed. The large rho(X) (rho(nuc) = -3.1 to -3.4) and beta(X) (beta(nuc) = 1.1-1.2) values seem to be characteristic of the anilinolysis of phosphates and thiophosphates with the Cl leaving group. Because of the relatively large size of the aniline nucleophile, the degree of steric hindrance could be the decisive factor that determines the direction of the nucleophilic attack to the phosphate and thiophosphate substrates with the relatively small-sized Cl leaving group.
Department of Chemistry, Inha University, Incheon, 402-751, Korea.
Md Ehtesham Ul
ME
Hoque
Nilay Kumar
NK
Dey
Chan Kyung
CK
Kim
Bon-Su
BS
Lee
Hai Whang
HW
Lee
D000588:Amines / Q000737:chemistry*; D000814:Aniline Compounds / Q000737:chemistry*; D002384:Catalysis; D006868:Hydrolysis; D007700:Kinetics; D008956:Models, Chemical; D015394:Molecular Structure; D010710:Phosphates / Q000737:chemistry*
D000588:Amines; D000814:Aniline Compounds; D010710:Phosphates; C035638:thiophosphoric acid