サイクロプロペンのエネ反応の移行構造
1Contribution from the Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, and the Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260.
Journal of the American Chemical Society
|November 19, 2013
まとめ
プロペンエチレン反応は,プロペンエチレン反応と比較して,著しく低い活性化バリアを示しており,実験結果と一致しています. エノフィールとしてサイクロプロペンのストレスの緩和は,これらのエネルギー的な違いを駆動します.
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:
- エネ反応は,アルケンがアリル水素と二重または三重結合を伴う基本的な有機変換である.
- サイクロプロペンは,圧縮されたサイクリックアルケーンであり,その高いリングストレンのためにユニークな反応性を提示します.
研究 の 目的:
- シクロプロペンをエノフィールとして含むエネ反応の移行構造とエネルギー学を調査する.
- 1つの反応におけるサイクロプロペンの反応性をプロペンの反応性と比較する.
主な方法:
- Ab initio分子軌道計算は, 6-31G* ベースセットを使用しています.
- 密度関数理論 (DFT) の計算は,Becke3LYP関数と6-31G*ベースセットを用いて行われました.
- 選択された移行構造のアクティブ・スペース・セルフ・コンシスタント・フィールド (CASSCF) 計算を完了します.
- エネルギー評価のための第2次モラー・プレセット (MP2) 混乱理論.
主要な成果:
- サイクロプロペンの反応は,プロペン-エチレン反応よりも実質的に低い活性化バリアを示します.
- トランジション構造は,基幹中間物質の安定性によって影響を受け,異なった程度の非同期性を表します.
- サイクロプロペンの二分化のためのエンドトランジション構造は,エクソ構造よりも2.7 kcal/molでエネルギー的に優れている.
結論:
- エノフィールとして作用するサイクロプロペンのストレスの緩和は,観察されたより低い活性化バリアの主要な理由です.
- 二次軌道重複は,サイクロプロペン二分化におけるエンドトランジション状態の好みを説明するために提案されています.
- 計算された二基間物質は,使用された理論的方法の人工物である可能性が高い.
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