KCS Publications

HOME > Search > Browsing(BKCS) > Archives

Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 29, Number 10
BKCSDE 29(10)
October 20, 2008

Title	Aminolysis of 2,4-Dinitrophenyl and 3,4-Dinitrophenyl Benzoates: Effect of ortho-Nitro Group on Reactivity and Mechanism
Author	Jin A Seo, Hye Min Lee, Ik Hwan Um*
Keywords	Aminolysis, Brønsted-type plot, Steric hindrance, Reaction mechanism, ortho-Effect
Abstract	Second-order rate constants (kN) have been measured spectrophotometrically for reactions of 3,4-dinitrophenyl benzoates (5b) with a series of alicyclic secondary amines in 80 mol % H2O/20 mol % DMSO at 25.0 ± 0.1 oC. The kinetic data have been compared with the data reported previously for the corresponding reactions of 2,4- dinitrophenyl benzoates (5a) to investigate the effect of changing the nucleofuge from 2,4-dinitrophenoxide to 3,4-dinitrophenoxide on reactivity and mechanism. The kinetic results show that aminolyses of 5a and 5b proceed through the same mechanism, i.e., a zwitterionic tetrahedral intermediate (T^±) with a change in the rate-determining step (RDS). Substrate 5a is more reactive than 5b when breakdown of T± is the RDS but less reactive when formation of T^± is the RDS. Dissection of kN values into the microscopic rate constants (e.g., k₁ and k₂/k_?1 ratio) has revealed that 5a results in larger k₂/k_?1 ratios but smaller k₁ values than 5b for all the amines studied. Since 2,4-dinitrophenoxide is less basic and a better nucleofuge than 3,4-dinitrophenoxide, the larger k₂/k_?1 ratios determined for the reactions of 5a than for those of 5b are as expected. The steric hindrance exerted by the ortho-nitro group on 5a contributes to the smaller k1 values found for the reactions of 5a than for those of 5b.
Page	1915 - 1919
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