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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 24, Number 2
BKCSDE 24(2)
February 20, 2003 

 
Title
Kinetics and Mechanism of the Addition of Benzylamines to Benzylidene Meldrum's Acids in Acetonitrile
Author
Hyuck Keun Oh, Tae Soo Kim, Hai Whang Lee*, Ikchoon Lee*
Keywords
Benzylidene Meldrum's acid, Nucleophilic addition reaction, Cross-interaction constant
Abstract
Nucleophilic addition reactions of benzylamines (XC6H4CH2NH2) to benzylidene Meldrum's acids (BMA; YC6H4CH=C(COO)2C(CH3)2) have been investigated in acetonitrile at 20.0 ℃. The rates of addition are greatly enhanced due to the abnormally high acidity of Meldrum's acid. The magnitudes of the Hammett (ρX and ρY) and Bronsted (βX) coefficients are rather small suggesting an early transition state. The sign and magnitude of the cross-interaction constant, ρXY (= -0.33), and kinetic isotope effects (kH/kD 1.5-1.7) involving deuterated benzylamine nucleophilies (XC6H4CH2ND2) are indicative of hydrogen-bonded cyclic transition state. The activation parameters, DH‡ 4 kcal mol-1 and DS‡ -37 e.u., are also in line with the proposed mechanism.
Page
193 - 196
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