ヴィニル炭素における核性置換のための構成の逆転対保持
R D Bach1, A G Baboul, H B Schlegel
1Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA.
Journal of the American Chemical Society
|June 14, 2001
まとめ
計算による研究では,ガス相核性ビニル基置換メカニズムが明らかになりました. 活性化されていないビニルクロライドはシグマ攻撃を好み,活性化されたダイハロエチレンはPI経路を好むが,どちらも高いエネルギーバリアを持っている.
科学分野:
- コンピューティング・ケミストリー
- 有機反応のメカニズム
背景:
- 核性ビニル置換 (Nu-V) は,有機合成において極めて重要です.
- ガス相メカニズムの理解は,反応性に関する基本的な洞察を提供します.
- 以前の研究では,Nu-V反応の複雑な経路が示唆されていた.
研究 の 目的:
- 核愛性ビニル置換のガス相機構を計算的に調査する.
- 異なるビニル基板の好ましい攻撃経路 (シグマ対パイ) を決定する.
- 反応経路における基質活性化と複合化の影響を分析する.
主な方法:
- クープレッド・クラスター・シングル・ダブルス (CCSD),CCSD (T),G2 (T+) を含む高レベルの計算方法が採用されました.
- ジオメトリの最適化は,CCSD/6-31+G* とCCSD(T)/6-31+G* を使用して行われました.
- 理論的な計算では,塩化アニオン (Cl-) とビニル塩化物および1-クロロ-1-フッ素エチレンとの反応を調査した.
主要な成果:
- 活性化されていないビニルクロライドは,単段階のシグマ攻撃を通じてガス相Nu-Vを経験します.
- 適度に活性化された1-クロロ-1-フッ素エチレンは,単段階のPI攻撃経路を好みます.
- Na(+) を併用しても,ビニル塩化物のシグマ偏好は変わらなかった.
- ガス相反応の計算された活性化バリアは,極めて高い.
結論:
- ガス相Nu-V反応は,基板活性化によって異なるシグマとパイ経路を示します.
- 高エネルギーバリアは,溶解とカウンターイオンが凝縮相反応に不可欠であることを示唆しています.
- 溶液中では,電子取り除く群が,カルバニオン中介物質を介してNu-Vを促進する可能性が高い.
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