Reactions of 2,4-Dinitrophenyl 5-substituted-2-thiophenecarboxylates with R2NH/R2NH2 + in 20 Mol % DMSO(aq). Effects of 5-Thienyl Substituent and Leaving Group on the Reaction Mechanism

Sang Yong Pyun, Kyu Cheol Paik, Man So Han, Bong-Rae Cho

Research output: Contribution to journalArticle

Abstract

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.

Original languageEnglish
JournalBulletin of the Korean Chemical Society
DOIs
Publication statusAccepted/In press - 2019 Jan 1

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Nucleophiles
Dimethyl Sulfoxide
Reaction rates
Carrier concentration
Carbon
Electrons
Substrates

Keywords

  • Aminolysis
  • Bronsted-plot
  • Hammett plot
  • Yukawa-Tsuno plot

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

@article{0f353a17f4444c05a2515e37416fa48d,
title = "Reactions of 2,4-Dinitrophenyl 5-substituted-2-thiophenecarboxylates with R2NH/R2NH2 + in 20 Mol {\%} DMSO(aq). Effects of 5-Thienyl Substituent and Leaving Group on the Reaction Mechanism",
abstract = "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 Br{\"o}nsted 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.",
keywords = "Aminolysis, Bronsted-plot, Hammett plot, Yukawa-Tsuno plot",
author = "Pyun, {Sang Yong} and Paik, {Kyu Cheol} and Han, {Man So} and Bong-Rae Cho",
year = "2019",
month = "1",
day = "1",
doi = "10.1002/bkcs.11857",
language = "English",
journal = "Bulletin of the Korean Chemical Society",
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TY - JOUR

T1 - Reactions of 2,4-Dinitrophenyl 5-substituted-2-thiophenecarboxylates with R2NH/R2NH2 + in 20 Mol % DMSO(aq). Effects of 5-Thienyl Substituent and Leaving Group on the Reaction Mechanism

AU - Pyun, Sang Yong

AU - Paik, Kyu Cheol

AU - Han, Man So

AU - Cho, Bong-Rae

PY - 2019/1/1

Y1 - 2019/1/1

N2 - 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.

AB - 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.

KW - Aminolysis

KW - Bronsted-plot

KW - Hammett plot

KW - Yukawa-Tsuno plot

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