Pt上でのアルキル群水素化の移行状態 ((111))
Pingping Ye1, Andrew J Gellman
1Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.
Journal of the American Chemical Society
|June 6, 2008
まとめ
プラチナ表面の置換効果は,水素化バリアに影響します. アルキル群の極化性と化度が増加すると,水素化のエネルギー障壁が上昇し,カチオンの移行状態を示します.
科学分野:
- 表面化学について
- カタリシス カタリシス カタリシス
- 物理化学 物理化学とは
背景:
- 置換剤効果を理解することは,触媒プロセスを設計する上で極めて重要です.
- Pt(111) 表面は,表面反応を研究するためのモデルシステムです.
研究 の 目的:
- Pt上にあるアルキル群の水素化移行状態に対する置換剤効果を調査する.
- 線形自由エネルギー関係を使用して,水素化バリアと置換剤の性質を相関させる.
主な方法:
- Pt上でのアルキルおよびフッ素アルキルイオジドの離散性アドソープション ((111)).
- 水素による共吸収に続いて,熱による脱吸収が行われます.
- 温度プログラム反応スペクトロスコピーは,水素化バリア (ΔE(H) ‡) を測定する.
主要な成果:
- 水素化バリアは,アルキル群の極化性と化度の両方とともに増加する.
- 置換定数とΔE(H) ‡の間の線形自由エネルギー関係が確立されました.
- フィールド反応常数 (ρF) = 27 ± 4 kJ/molと偏極化反応常数 (ρα) = 19 ± 3 kJ/molを決定した.
結論:
- Pt(111) 上のアルキル群水素化の過渡状態は,わずかにカチオンの性質を示す.
- 置換効果は,表面反応エネルギーを著しく調節する.
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