Collect. Czech. Chem. Commun. 2004, 69, 2174-2182

Kinetics and Mechanism of the Aminolysis of S-Aryl O-Ethyl Dithiocarbonates in Acetonitrile

Hyuck Keun Oha, Ji Young Oha, Dae Dong Sungb and Ikchoon Leeb,c,*

a Department of Chemistry, Chonbuk National University, Chonju 560-756, Korea
b Department of Chemistry, Dong-A University, Busan 604-714, Korea
c Department of Chemistry, Inha University, Inchon 402-751, Korea


The aminolysis of S-aryl O-ethyl dithiocarbonates with benzylamines are studied in acetonitrile at -25.0 °C. The βXnuc) values are in the range 0.67-0.77 with a negative cross-interaction constant, ρXZ = -0.24, which are interpreted to indicate a concerted mechanism. The kinetic isotope effects involving deuterated benzylamine nucleophiles (XC6H4CH2ND2) are large, kH/kD = 1.41-1.97, suggesting that the N-H(D) bond is partially broken in the transition state by forming a hydrogen-bonded four-center cyclic structure. The concerted mechanism is enforced by the strong push provided by the EtO group which enhances the nucleofugalities of both benzylamine and arenethiolate from the putative zwitterionic tetrahedral intermediate.

Keywords: S-Aryl O-ethyl dithiocarbonates; Aminolysis; Concerted mechanism; Cross-interaction constants; Kinetic isotope effects; Reaction mechanisms.

References: 39 live references.