水素結合フェノールの酸化における協調した陽子電子移転
Ian J Rhile1, Todd F Markle, Hirotaka Nagao
1Department of Chemistry, Campus Box 351700, University of Washington, Seattle, Washington 98195-1700, USA.
Journal of the American Chemical Society
|May 4, 2006
まとめ
フェノールとペンダント塩基を含むプロトン結合電子移転反応 (PCET) を研究した. これらの反応は,段階的なメカニズムではなく,協調された陽子電子移転 (CPET) により起こり,有意な再構成エネルギーが発生します.
科学分野:
- 物理化学 物理化学
- 電気化学 電気化学について
- 化学動力学 化学動力学
背景:
- ペンダント水素結合塩基 (HOAr-B) のフェノルは,陽子結合電子移転 (PCET) を研究するためのモデルシステムです.
- PCETのメカニズムの理解は,様々な化学的および生物学的プロセスに不可欠です.
研究 の 目的:
- アセトニトリルにおけるペンダント水素結合塩基 (プライマリーアミン,イミダゾール,ピリジン) の3つのフェノールの酸化機構を調査する.
- レドックスポテンシャルと反応経路を決定し,特に協調型陽子電子移転 (CPET) と段階的なメカニズムを区別する.
- これらのPCET反応の運動学と熱力学を電気化学的および化学的方法を使用して分析する.
主な方法:
- 様々な単電子酸化剤を用いた化学的酸化.
- 準逆の電気化学的酸化である.
- 熱化学的議論の分析,運動的同位体効果,および機械的解明のためのマーカス理論.
主要な成果:
- 酸化産物は,塩基に陽子移転するフェノキシル基で, (*) OAr-BH (((+),PCETプロセスを示す.
- レドックス電位は,陽子伝達の推進力により低下します.
- 証拠は,初期電子または陽子移転を排除する協調された陽子-電子移転 (CPET) メカニズムを強く支持しています.
- 大量の再構成エネルギー (λ = 2356 kcal mol−1) がCPETで観察されました.
- 異質な電子移転の速度定数は,アディアバティック・マルカス理論の予測と一致しています.
結論:
- ペンダント塩基によるフェノールの酸化は,CPETメカニズムによって行われます.
- 観測された運動学と熱力学は,アディアバティック・マーカス理論と一致しています.
- これらの発見は,陽子と電子の移転が異なる場所に行われるCPET反応の詳細な洞察を提供します.
![Protein Film Infrared Electrochemistry Demonstrated for Study of H2 Oxidation by a [NiFe] Hydrogenase](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F55858.jpg&w=3840&q=50)
関連する概念動画
02:21Oxidation of Alkenes: Syn Dihydroxylation with Potassium Permanganate
Alkenes can be dihydroxylated using potassium permanganate. The method encompasses the reaction of an alkene with a cold, dilute solution of potassium permanganate under basic conditions to form a cis-diol along with a brown precipitate of manganese dioxide.
02:04Oxidation of Alkenes: Anti Dihydroxylation with Peroxy Acids
Diols are compounds with two hydroxyl groups. In addition to syn dihydroxylation, diols can also be synthesized through the process of anti dihydroxylation. The process involves treating an alkene with a peroxycarboxylic acid to form an epoxide. Epoxides are highly strained three-membered rings with oxygen and two carbons occupying the corners of an equilateral triangle. This step is followed by ring-opening of the epoxide in the presence of an aqueous acid to give a trans diol.
02:47Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
Introduction
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
01:17Oxidation of Phenols to Quinones
In the presence of oxidizing agents, phenols are oxidized to quinones. Quinones can be easily reduced back to phenols using mild reducing agents. The electron-donating hydroxyl group enhances the reactivity of the aromatic ring, enabling oxidation of the ring even in the absence of an α hydrogen.
o-hydroxy phenols are oxidized to o-quinones and p-hydroxy phenols to p-quinones. Such redox reactions involve the transfer of two electrons and two protons. The reversible redox property is crucial in...
o-hydroxy phenols are oxidized to o-quinones and p-hydroxy phenols to p-quinones. Such redox reactions involve the transfer of two electrons and two protons. The reversible redox property is crucial in...
01:19Phase I Reactions: Oxidation of Aliphatic and Aromatic Carbon-Containing Systems
Phase I biotransformation reactions are integral to drug metabolism, predominantly involving oxidative, reductive, and hydrolytic transformations. Chief among these are oxidative reactions, which enhance the hydrophilicity of xenobiotics and introduce polar functional groups to facilitate their elimination from the body.
Oxidation reactions are fundamental in aromatic carbon-containing systems. An example is the hydroxylation of phenobarbital, a process that transforms it into...
Oxidation reactions are fundamental in aromatic carbon-containing systems. An example is the hydroxylation of phenobarbital, a process that transforms it into...
01:15Phase I Reactions: Oxidation of Carbon-Heteroatom and Miscellaneous Systems
Oxidative reactions are pivotal in metabolizing numerous compounds, including pharmaceutical drugs. These reactions often occur in carbon-heteroatom systems, such as carbon-nitrogen, carbon-sulfur, and carbon-oxygen.
In carbon-nitrogen systems, aliphatic and aromatic amines can undergo oxidative reactions. Secondary and tertiary amines, like those found in tricyclic antidepressants, can undergo N-dealkylation, a process that involves the oxidation of the alkyl group. In addition, oxidative...
In carbon-nitrogen systems, aliphatic and aromatic amines can undergo oxidative reactions. Secondary and tertiary amines, like those found in tricyclic antidepressants, can undergo N-dealkylation, a process that involves the oxidation of the alkyl group. In addition, oxidative...