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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 24, Number 1
BKCSDE 24(1)
January 20, 2003 

Kinetics and Mechanism of the Aminolysis of O-Methyl-S-Phenylthiocarbonates in Methanol
Ho Bong Song, Moon Ho Choi, In Sun Koo, Hyuck Keun Oh, Ikchoon Lee
O-Methyl-S-phenylthiocarbonates, Stepwise mechanism, Zwitterionic tetrahedral intermediate, Cross-interaction constant
Kinetic studies of the reaction of O-methyl-S-phenylthiocarbonates with benzylamines in methanol at 45.0 oC have been carried out. The reaction proceeds by a stepwise mechanism in which the rate-determining step is the breakdown of the zwitterionic tetrahedral intermediate, T±, with a hydrogen-bonded four-center type transition state (TS). These mechanistic conclusions are drawn based on (i) the large magnitude of rX and rZ, (ii) the normal kinetic isotope effects (kH/kD > 1.0) involving deuterated benzylamine nucleophiles, (iii) the positive sign of rXY and the larger magnitude of rXZ than that for normal SN2 processes, and lastly (iv) adherence to the reactivity-selectivity principle (RSP) in all cases.
91 - 94
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