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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 23, Number 10
BKCSDE 23(10)
October 20, 2002 

Kinetic Studies on the Nucleophilic Addition Reactions of Vinylic β-Diketones
Hyuck Keun Oh, Jae Myon Lee
Nucleophilic addition reaction, Single-step process, Cross-interaction constant, Kinetic isotope effect, Four-center cyclic transition state
The kinetics of the addition of X-substituted benzylamines (BA) to Y-substituted Benzylideneacetylacetones (BAA) have been investigated in acetonitrile at 25.0℃. The reaction is studied under pseudo-first-order conditions by keeping a large excess of BA over BAA. The addition of BA to BAA occurs in a single step in which the addition of BA to Cα of BAA and proton transfer from BA to Cβ of BAA take place concurrently with a four-membered cyclic transition state structure. The magnitude of the Hammett ( ρx) and Bronsted ( βx) coefficients are rather small suggesting an early tansition state (TS). The sign and magnitude of the cross-interaction constant, ρXY (= -0.49), is comparatible to those found in the normal bond formation processes in the SN2 and addition reactions. The normal kinetic isotope effect (kH/kD > 1.0) and relatively low DH and large negative DS values are also consistent with the mechanism proposed.
1459 - 1462
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