Bulletin of the Korean Chemical Society

  • 제34권4호
  • /
  • Pages.1030-1034
  • /
  • 2013
  • /
  • 0253-2964(pISSN)
  • /
  • 1229-5949(eISSN)
대한화학회 (Korean Chemical Society)
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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

  • 투고 : 2012.12.26
  • 심사 : 2013.01.03
  • 발행 : 2013.04.20
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초록

Elimination reactions of $(E)-2,4-(NO_2)_2C_6H_2CH=NOC_6H_3-2-X-4-NO_2$ (1a-e) promoted by $R_3N/R_3NH^+$ in 70 mol % MeCN(aq) have been studied kinetically. The reactions are second-order and exhibit Br$\ddot{o}$nsted ${\beta}$ = 0.80-0.84 and ${\mid}{\beta}_{lg}{\mid}$ = 0.39-0.42, respectively. For all leaving groups and bases employed in this study, the ${\beta}$ and ${\mid}{\beta}_{lg}{\mid}$ values remained almost the same. The results can be described by a negligible $p_{xy}$ interaction coefficient, $p_{xy}={\partial}{\beta}/pK_{lg}={\partial}{\beta}_{lg}/pK_{BH}{\approx}0$, 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 $R_3N/R_3NH^+$-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.

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참고문헌

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피인용 문헌

  1. in 70 mol% MeCN (aq). Effects of the β-Aryl Group and Leaving Group on Nitrile-Forming Transition States vol.37, pp.6, 2016, https://doi.org/10.1002/bkcs.10791