トリフェニルメチル誘導体によるパウリ反発とロンドンの分散の微妙なバランスを探す
Sören Rösel1, Jonathan Becker2, Wesley D Allen
1Institute of Organic Chemistry , Justus Liebig University , Heinrich-Buff-Ring 17 , 35392 Giessen , Germany.
Journal of the American Chemical Society
|October 6, 2018
まとめ
ロンドン分散相互作用は,ヘキサフェニルエタン (HPE) 誘導体を著しく安定させる. アダマンチルなどの大きな硬い炭化水素群は,溶液中でも,有利な幾何学的な適合と強い分子内分散力によってHPEの安定性を高めます.
科学分野:
- 物理有機化学
- 超分子化学
- コンピュータ化学
背景:
- ロンドン分散 (LD) 相互作用は化学における基本的,無所不在な力である.
- ヘキサフェニルエタン (HPE) 誘導体は,固有の不安定性で知られている.
- HPEの安定性に寄与する要因を理解することは,分子設計において極めて重要です.
研究 の 目的:
- ヘクサフェニルエタン誘導体の安定化におけるロンドンの分散相互作用の役割を調査する.
- 新しい全メタヒドロカルビル置換トリフェニルメチル (TPM) 誘導体を合成し,特徴づけること.
- HPEの安定性に対する異なる置換剤の安定効果を定量化する.
主な方法:
- 全メタヒドロカルビル置換のTPM誘導体の一連の合成
- 構造的特徴化のための単結晶X線微分法 (SC-XRD).
- 核磁共鳴 (NMR),電子パラマグネティック共鳴 (EPR),UV-Visスペクトロスコーピー
- 温度依存解離定数分析と計算モデル化 (B3LYP-D3 ((BJ) /def2-TZVPP ((C-PCM)).
主要な成果:
- SC-XRDは,二次的なHPE構造におけるメタ置換物,特にターチル・ブチルおよびアダマンチルなどの大型のグループ間の優れた幾何学的な適合性を明らかにした.
- 顕微鏡データでは,トリチル基のエスカフォードに対する全メタアルキル置換の限界的な電子効果を示した.
- 熱力学的分析により,全メタターチル-ブチル-HPE (0.3(5) kcal mol−1) と全メタアダマンチル-HPE (2.1(6) kcal mol−1) の実験的な解離自由エネルギー (ΔGd298) が得られた.
- 計算上の研究により,実験結果が裏付けられ,置換物の大きさが増加するにつれて安定する傾向が示された.
結論:
- ロンドン分散相互作用は,ヘクサフェニルエタン誘導体の主要な安定化因子である.
- 大きく,硬く,対称な炭化水素分子は,効率的な分散エネルギードナーである.
- 最適な幾何学的なフィットにより,これらの分子はHPEのような不安定な分子を強い分子内LD相互作用によって安定させ,溶液でも持続します.
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