Reactions of 2,4-dinitrophenyl 2-thiophenecarboxylate (2a–d) with R2NH/R2NH2 + in 20 mol % DMSO(aq) have been studied. The reactions are overall second order, first order to the substrates, and first order to the nucleophiles. The Brönsted plots showed downward curves with pKa 0 = 9.5, β1 = 0.22–0.34, and β2 = 0.85–0.92. The k1 values increased with a stronger electron-withdrawing 5-thienyl substituent and a stronger nucleophile, whereas the k2/k−1 values remained nearly the same for all 5-thienyl substituents. The influence of 5-thienyl substituent on the reaction rates showed excellent correlations on the Yukawa-Tsuno plots with ρ = 1.28–2.16 and r = 0.20–0.60. The ρ value increased and r value decreased with a stronger nucleophile, indicating an increase in the electron density at the carbonyl carbon and a decrease in the resonance demand. From these results, a stepwise mechanism with a change in the rate-determining step has been proposed.
|Number of pages||8|
|Journal||Bulletin of the Korean Chemical Society|
|Publication status||Published - 2019 Oct 1|
- Hammett plot
- Yukawa-Tsuno plot
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