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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 (ρ_X and ρ_Y) and Bronsted (β_X) coefficients are rather small suggesting an early transition state. The sign and magnitude of the cross-interaction constant, ρ_XY (= -0.33), and kinetic isotope effects (k_H/k_D 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
Full Text	PDF

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