陽子化されたベンゼンは,鉄トリカルボニル基の協調によってどのくらい安定化されますか?
Martin Galvin1, J Peter Guthrie, Claire M McDonnell
1School of Chemistry and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland.
Journal of the American Chemical Society
|December 20, 2008
まとめ
鉄トリカルボニル (Fe ((CO)) 3) グループは,サイクロヘキサジニルカチオンを著しく安定させ,酸性を下げ,水解速度を変更する. この調整は,有機イオンの安定性と反応性に影響する.
科学分野:
- 有機金属化学 有機金属化学
- 反応の動力学
- コンピューティング・ケミストリー
背景:
- 有機カチオンの反応性は,様々な化学プロセスにおいて極めて重要です.
- 有機イオンの安定性に対する金属の調整の影響を理解することが鍵となる.
研究 の 目的:
- Fe(CO) 3の調整がサイクロヘキサジニルカチオンの水解と酸性に対する影響を調査する.
- 調整されたおよび調整されていないサイクロヘキサディエニルイオンの反応性を比較する.
主な方法:
- サイクロヘキサジニルカチオン水解の運動と均衡の測定.
- エネルギー転送の推定のための密度関数理論 (DFT) 計算. エネルギー転送の推定のための密度関数理論 (DFT) 計算.
主要な成果:
- Fe(CO) 3の調整により,サイクロヘキサジニルカチオンのpKRが−2.1から4.7に上昇する.
- 協調カチオンの水解は,エンドイゾーマーよりも107倍のエクソイゾーマー形成を好む.
- DFTの計算では,調整カチオンのデプロトネーションのpKaを8と推定しています.
結論:
- Fe(CO) 3の調整により,サイクロヘキサジニルカチオンの酸度 (46 kcal/mol) が劇的に低下する.
- 水解における観察されたステレオ選択性は,同位体安定性の違いによるものではない.
- 金属調整は,有機中間物質の性質を調節するための強力な戦略を提供します.
関連する概念動画
Electrophilic Aromatic Substitution: Nitration of Benzene
The nitration of benzene is an example of an electrophilic aromatic substitution reaction. It involves the formation of a very powerful electrophile, the nitronium ion, which is linear in shape. The reaction occurs through the interaction of two strong acids, sulfuric and nitric acid.
Electrophilic Aromatic Substitution: Chlorination and Bromination of Benzene
Chlorination and bromination are important classes of electrophilic aromatic substitutions, where benzene reacts with chlorine or bromine in the presence of a Lewis acid catalyst to give halogenated substitution products. A Lewis acid such as aluminium chloride or ferric chloride catalyzes the chlorination, and ferric bromide catalyzes the bromination reactions. During the bromination of alkenes, bromine polarizes and becomes electrophilic. However, in the bromination of benzene, the bromine...
Structure of Benzene: Kekulé Model
In 1865, August Kekule suggested the structure of benzene according to the structural theory of organic chemistry based on the three assertions—formula of benzene is C6H6, all the hydrogens of benzene are equivalent, and each carbon must have four bonds due to its tetravalency.
He proposed that benzene has a cyclic structure of six carbon atoms attached to one hydrogen atom each, with three alternating pi bonds.
He proposed that benzene has a cyclic structure of six carbon atoms attached to one hydrogen atom each, with three alternating pi bonds.
Electrophilic Aromatic Substitution: Sulfonation of Benzene
Sulfonation of benzene is a reaction wherein benzene is treated with fuming sulfuric acid at room temperature to produce benzenesulfonic acid. Fuming sulfuric acid is a mixture of sulfur trioxide and concentrated sulfuric acid.
Reduction of Benzene to Cyclohexane: Catalytic Hydrogenation
Unlike the easy catalytic hydrogenation of an alkene double bond, hydrogenation of a benzene double bond under similar reaction conditions does not take place easily. For example, in the reduction of stilbene, the benzene ring remains unaffected while the alkene bond gets reduced. Hydrogenation of an alkene double bond is exothermic and a favorable process. In contrast, to hydrogenate the first unsaturated bond of benzene, an energy input is needed; that is, the process is endothermic. This is...
Valence Bond Theory
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...


