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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 35, Number 7
BKCSDE 35(7)
July 20, 2014 

Kinetic Study on Aminolysis of 4-Nitrophenyl Isonicotinate in Acetonitrile: Effect of Amine Basicity on Reactivity and Reaction Mechanism
Minah Shin, Min-Young Kim, Ik-Hwan Um*
Aminolysis, 4-Nitrophenyl isonicotinate, Energy profile, Stepwise mechanism, Catalysis
A kinetic study is reported on nucleophilic substitution reactions of 4-nitrophenyl isonicotinate (7) with a series of cyclic secondary amines in MeCN. The plots of kobsd vs. [amine] curve upward for the reactions with weakly basic amines (e.g., morpholine, 1-(2-hydroxyethyl)piperazine, and piperazine) but are linear for those with strongly basic amines (e.g., piperidine and 3-methylpiperidine). The curved plots for the reactions with the weakly basic amines are typical for reactions reported previously to proceed through uncatalyzed and catalyzed routes with two intermediates (e.g., a zwitterionic tetrahedral intermediate T± and its deprotonated form T–). In contrast, the linear plots for the reactions with the strongly basic amines indicate that the catalytic route (i.e., the deprotonation process to yield T– from T± by a second amine molecule) is absent. The Brønsted-type plots for Kk2 and Kk3 (i.e., the rate constants for the uncatalyzed and catalyzed routes, respectively) exhibit excellent linear correlations with βnuc = 0.99 and 0.69, respectively. The effect of amine basicity on the reaction mechanism is discussed in detail.
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