N-アセチラミノ-p-メチラセトフェノン系におけるケトエノール/エノラートバランス. ベータ窒素置換剤の効果
Y Chiang1, A G Griesbeck, H Heckroth
1Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada.
Journal of the American Chemical Society
|September 13, 2001
まとめ
N-アセチラミノ置換剤は,N-アセチラミノ-p-メチラセトフェノンのケトエノールバランスと酸性定数を大幅に増加させます. この置換剤は,また,酸触媒によるエノールケトニゼーションの速度を劇的に遅らせる.
科学分野:
- 有機化学 オーガニック・ケミストリー
- 物理有機化学 物理有機化学
- 反応の動力学
背景:
- ケトンエノル化に対する置換剤の電子効果を理解することは,有機化学において極めて重要です.
- ケトン・エノール・タウトメリスムの酸性および均衡に対するN-アセチラミノ群の影響は,詳細な調査を必要とします.
研究 の 目的:
- P-メチラセトフェノンのケトエノールバランスと酸性に対するN-アセチラミノ置換物の影響を定量化するために.
- 様々な条件下でN-アセチラミノ-p-メチラセトフェノンのエノ化とケトン化率を決定する.
主な方法:
- フラッシュ光分解により,シスエノール中間産物が生成されました.
- ケトン化速度は,酸性および塩基性溶液,およびさまざまなバッファシステムで測定されました.
- エノライゼーション率は,メチレン陽子の水素交換によって決定された.
主要な成果:
- ケトエノール均衡定数 (K(E)) は5.33.3であることが判明しました.
- エノール (Q) (a) (E)) とケトン (Q) (a) (K)) の酸性定数は,それぞれ9.12と14.45と決定されました.
- N-アセチラミノ置換剤は,K (((E)) を3桁,Q (((a) ((E)) を1桁,Q (((a) ((K)) を4桁増加させ,同時にH+触媒によるケトニゼーションを4桁遅らせました.
結論:
- N-アセチラミノ群は,エノール形態を著しく安定させ,エノールとケトンの両方のタウトマーの酸度を変化させます.
- 観察された置換効果は,平衡と反応経路に対する電子の影響に起因する.
- この研究は,ケトン化学における電子提供置換物の影響に関する定量的なデータを提供します.
関連する概念動画
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