酸 は,ニトロキシド の 抗酸化 作用 の 鍵 に なっ て い ます
Evan A Haidasz1, Derek Meng1, Riccardo Amorati2
1Department of Chemistry, University of Ottawa , Ottawa, Ontario K1N 6N5, Canada.
Journal of the American Chemical Society
|March 30, 2016
まとめ
TEMPOのような持続的なダイアルキルニトロキシドは,阻害されたアミン光安定剤の鍵です. この研究は,TEMPOがアルキル基によって再生され,抗酸化作用が説明される別のメカニズムを示しています.
科学分野:
- 有機化学
- ポリマー科学
- 材料科学
背景:
- 2,2,6,6-テトラメチルピペリジン-1-オキシル (TEMPO) などの持続的なダイアルキルニトロキシドは,阻害アミン光安定剤 (HALS) の重要な成分です.
- HALS添加物は,様々な消費者および産業製品の光酸化分解を防止します.
- HALSの確立されたメカニズムは,窒素酸化物,アルキルラジカル,および過酸化ラジカルによる触媒サイクルを含む.
研究 の 目的:
- 持続的なダイアルキルニトロキシドの (光) 酸化分解の代替反応機構の証拠を提供すること.
- 酸化窒素と過酸化ラジカルとの反応における酸触媒の役割を調査する.
- アルキルラジカルによるオキシアンモニウムイオンからのTEMPOの再生経路を解明する.
主な方法:
- TEMPOとペロキシルラジカルとの反応の動的研究.
- TEMPOのオクソアモニウムイオンとアルキル基間の反応の速度常数の決定
- 高温での炭化水素の自己酸化における反応機構の調査.
主要な成果:
- TEMPOは,過酸化ラジカルと 拡散制御された速度で反応します.
- TEMPOのオキシアンモニウムイオンからアルキルラジカルによる再生は,約1−3×10 M−1 s−1の速度定数で起こります.
- この再生経路はアルキル基に対して O2 と効果的に競合し,その速度は酸の強度によって影響されます.
結論:
- HALSにおける窒素酸化物の活性に対する代替的酸触媒メカニズムが提案され,オキソアンモニアムイオン形成とアルキル基による減少を伴う.
- このメカニズムは,炭化水素の自己酸化で観察されたTEMPOの触媒的根幹捕獲抗酸化活性を説明します.
- この発見は,HALSとTEMPOベースの抗酸化物質の有効性の基礎となる化学的性質の理解に寄与する.
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