Elimination reactions of (E)-2,4,6-trinitrobenzaldehyde O-benzoyloximes promoted by R2NH/R2NH2 + in 70 mol% MeCN (aq). Effects of the β-aryl group and leaving group on nitrile-forming transition states

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

Research output: Contribution to journalArticle

Abstract

Elimination reactions of (E)-2,4,6-(NO2)3C6H2CH=NOC(O)C6H4X (3) promoted by R2NH/R2NH2 + in 70 mol% MeCN (aq) have been studied. The reactions produced elimination products and exhibited second-order kinetics. The β and |β1g| values remained nearly the same for all leaving groups and bases. The results can be described by the negligible pxy interaction coefficient, pxy = ∂β/∂pKlg = ∂βlg/∂pKBH ≈ 0, which provides a strong support for the (E1cb)irr mechanism. For eliminations from (E)-ArCH NOC=(O)C6H4X (1, 3) and (E)-2,4,6-(NO2)3C6H2CH=NOAr′ (2, 3), the change of the β-aryl group (Ar) from 2,4-dinitrophenyl (1) to 2,4,6-trinitrophenyl (3) increased the rate by 270-fold without appreciable change in the transition state structure. On the other hand, the leaving group (OAr′) variation from benzoate (3) to 4-nitrophenoxy (2) induced a change in reaction mechanism from (E1cb)irr to E2. These results have been attributed to the cyclic transition state for the nitrile-forming eliminations involving the benzoate leaving group.

Original languageEnglish
Pages (from-to)871-876
Number of pages6
JournalBulletin of the Korean Chemical Society
Volume37
Issue number6
DOIs
Publication statusPublished - 2016 Jun 1

Keywords

  • E2 and (E1cb)
  • Elimination
  • Mechanism
  • β-aryl group and leaving group effect

ASJC Scopus subject areas

  • Chemistry(all)

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