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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 20, Number 12
BKCSDE 20(12)
December 20, 1999 

Kinetics and Mechanism of the Aminolysis of Thiophenyl Acetates in Acetonitrile
Hyuck Keun Oh, Jin Hee Yang, Hai Whang Lee, Ikchoon Lee
Kinetics and mechanism of the aminolysis of Z-thiophenyl acetates with X-benzylamines are investigated in acetonitrile at 45.0℃. The magnitudes of Bronsted coefficients βx (=1.3~-1.6) and βz (= -2.1~-2.4) are all large and cross-interaction constant ρxz is relatively large and positive (0.90). These trends are consistent with the rate-limiting breakdown of a tetrahedral intermediate, T±. The proposed mechanism is also supported by adherence of the rate data to the reactivity-selectivity principle (RSP). The kinetic isotope effects, kH/kD, are greater than unity (1.3-1.4) suggesting a possibility of hydrogen-bonded four-centered transition state. The activation parameters, ΔH ≠ and ΔS ≠ , are consistent with this transition-state structure.
1418 - 1420
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