Eliminations from (E)-2,4-dinitrobenzaldehyde O-aryloximes promoted by R3N/R3NH+ in 70 mol% MeCN(aq). Effects of leaving group and base-solvent on the nitrile-forming transition-state

Bong-Rae Cho, Sang Yong Pyun

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Abstract

Elimination reactions of (E)-2,4-(NO2)2C 6H2CH=NOC6H3-2-X-4-NO2 (1a-e) promoted by R3N/R3NH+ in 70 mol % MeCN(aq) have been studied kinetically. The reactions are second-order and exhibit Brönsted β = 0.80- 0.84 and |βlg| = 0.39-0.42, respectively. For all leaving groups and bases employed in this study, the β and |βlg| values remained almost the same. The results can be described by a negligible pxy interaction coefficient, pxy = δβ/pKlg = δβlg/pK-azip ̃ 0, which describes the interaction between the base catalyst and the leaving group. The negligible pxy interaction coefficient is consistent with the (E1cb) irr mechanism. Change of the base-solvent system from R 3N/MeCN to R3N/R3NH+-70 mol % MeCN(aq) changed the reaction mechanism from E2 to (E1cb)irr. Noteworthy was the relative insensitivity of the transition state structure to the reaction mechanism change.

Original languageEnglish
Pages (from-to)1030-1034
Number of pages5
JournalBulletin of the Korean Chemical Society
Volume34
Issue number4
DOIs
Publication statusPublished - 2013 Apr 20

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Keywords

  • E1cb-like and (E1cb)
  • Elimination
  • Leaving group and base-solvent effect

ASJC Scopus subject areas

  • Chemistry(all)

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