モノヒドリックアルコールを含んだ水溶液中の水嫌性のエステルによって形成された,水嫌性安定化遭遇複合体の動的証拠

N J Buurma¹, L Pastorello, M J Blandamer

¹Physical Organic Chemistry Unit, Stratingh Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.

Journal of the American Chemical Society

|November 29, 2001

まとめ

エステルの水解速度は,エタノールなどのアルコールを添加すると低下し,エタノールは接触複合体を安定させます. この水嫌性安定化作用は,水を阻害することで,反応運動に影響する.

科学分野:

物理有機化学物理有機化学
溶液化学について
化学動力学化学動力学

背景:

エステル水解は,有機化学における基本的な反応である.
化学反応速度に対する溶媒の影響を理解することは,化学的振る舞いを予測する上で極めて重要です.

研究の目的:

4つの特定のエステルのpHに依存しない水解を調査する.
エステル水解速度に対する様々なアルコールコソルト (エタノール,1-プロパノール,1-ブタノール) の影響を分析する.
これらの観測された媒体の効果の背後にある運動および熱力学的メカニズムを解明する.

主な方法:

水溶液中のp-メトキシフェニル2,2-ジクロロアルカノアートの中性水解速度を研究した.
添加されたモノヒドリックアルコールコソルトのモラリティが変化した.
速度常数変化を分析するために熱力学および運動モデルを適用した.

主要な成果:

水解速度の定数は,コソリュート濃度が増加するにつれて減少した.
エステルとアルコールコソルトの両方の排水性と相関する運動媒体の効果.
水害性相互作用によって安定するコンプレックス形成は,主なメカニズムとして特定されました.

結論:

コソルートとエステルの間の水性相互作用は,水解運動学を著しく影響する.
遭遇複合体は,反応の初期状態を安定させ,速度を下げます.
活性化エンタルピーとエントロピーの観察された変化は,水害性安定化モデルを支持する.

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