Departmental Bulletin Paper ベンゾエートアニオンの気相安定性に及ぼす置換基効果の二面角依存性

中田, 和秀  ,  藤尾, 瑞枝

30pp.27 - 35 , 2016-4-1 , 法政大学情報メディア教育研究センター
ISSN:18807526
Description
ベンゼン環とCOO平面がなす二面角を多様に固定した環置換ベンゾエートアニオンの相対気相安定性を計算化学的に決定した。得られた置換基効果を拡張湯川−都野式によって解析した。二面角の増大に伴ってr値は顕著に増加した。r値に反映される直接共鳴効果の作用機構を解明するため,NBO解析を行った。その結果,二面角が大きいときには側鎖の酸素原子の非共有電子対からベンゼンπ電子系への電子移動が観測され,これがr値増大の原因であることが明らかになった。
Relative gas-phase stabilities of ring-substituted benzoate anions, of which the dihedral angle φ between the benzene ring and the COO – planes was fixed, were computationally determined utilizing isodesmic reactions. The energies of respective species involved in the reactions were calculated by B3LYP/6-311+G(2d,p) level of theory. The φ was varied from 0˚ to 90˚ by steps of 10˚. Obtained 10 kinds of substituent effects were analyzed by an extended Yukawa-Tsuno equation: –Δ E X =ρ (σ 0 + r − Δσ R − + s Δσ S Resultant r – value increased from -0.03 (φ=0˚) to 0.38 (φ=90˚) with the increase of the φ. To reveal the mechanism of the through-resonance in benzoate anions, NBO analyses were performed. It has become apparent that the donation of electrons from the lone pairs on the O atoms to the benzene π-electron system is crucial to the through-resonance in twisted benzoate anions. Keywords : Substituent Effect, Benzoate Anion, Extended Yukawa-Tsuno Equation, DFT calculation, NBO Analysis
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