KCS Publications

HOME > Search > Browsing(BKCS) > Archives

Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 35, Number 6
BKCSDE 35(6)
June 20, 2014

Title	Kinetic Study on Nucleophilic Substitution Reaction of 5-Nitro-8-quinolyl Benzoate, Picolinate, Nicotinate and Isonicotinate with Alkali Metal Ethoxide: Effect of Nonleaving Group on Reactivity and Transition State Structure
Author	Jieun Lee, Min-Young Kim, Ik-Hwan Um*
Keywords	Metal ion catalysis, Reaction mechanism, Transition state, Electrophilicity, Nucleofugality
Abstract	Pseudo-first-order rate constants (kobsd) have been measured spectrophotometrically for the reactions of 5-nitro- 8-quinolyl nicotinate (4) and 5-nitro-8-quinolyl isonicotinate (5) with alkali metal ethoxides (EtOM; M = K, Na and Li) in anhydrous ethanol at 25.0 ± 0.1 oC. The plots of kobsd vs. [EtOM] curve slightly upward for the reactions with EtOK and EtONa but are linear for the reactions with EtOLi and for those with EtOK in the presence of 18-crown-6-ether. Dissection of kobsd into kEtO− and kEtOM (i.e., the second-order rate constants for the reactions with the dissociated EtO– and ion-paired EtOM, respectively) has revealed that the reactivity increases in the order EtO– ≈ EtOLi < EtOK < EtONa for the reactions of 4 and EtOLi < EtO– < EtOK < EtONa for the reactions of 5. Comparison of the kinetic results for the reactions of 4 and 5 with those reported previously for the corresponding reactions of 5-nitro-8-quinolyl benzoate (2) and picolinate (3) has revealed that the esters possessing a pyridine ring (i.e., 3-5) are significantly more reactive than the benzoate ester 2 due to the presence of the electronegative N atom (e.g., 2 << 3 < 4 < 5). It has been concluded that M+ ion catalyzes the reactions of 3-5 by increasing the electrophilicity of the reaction center through a five-membered cyclic transition state (TS) for the reaction of 3 and via a four-membered cyclic TS for the reactions of 4 and 5.
Page	1789 - 1793
Full Text	PDF

How to access to the WOL for The Bulletin of the Korean Chemical Society ?

The Bulletin of the Korean Chemical Society will be co-published with Wiley-VCH from 2015 towards. The online version of the Journal will thus be available on Wiley Online Library, Wiley(-VCH)'s global online platform.

KCS members can get a free online access to the Bulletin of the Korean Chemical Society in WOL.

Free Access to WOL