原子酸素を持つ金属基板に成長したグラフェンの機能化:エノラート vs エポキシード
Jaehoon Jung1, Hyunseob Lim, Junepyo Oh
1Surface and Interface Science Laboratory, RIKEN , Wako, Saitama 351-0198, Japan.
Journal of the American Chemical Society
|June 3, 2014
まとめ
エピタキシアルグラフェンの原子酸化により,安定したグラフェンエノラート,新しい中間物質が形成されます. この発見は,グラフェンの機能化と,触媒とデバイスにおける応用のための新しい経路を提供します.
科学分野:
- マテリアルサイエンス 材料科学
- 表面化学について
- コンピューティング・ケミストリー
背景:
- グラフェンの機能化は,高度な材料や触媒の開発に不可欠です.
- グラフェンの表面化学を制御することは,様々な用途での潜在能力を解き放つための鍵です.
研究 の 目的:
- エピタキシアルグラフェンにおける原子酸化のメカニズムを調査する.
- グラフェンの新しい機能化経路と中間物質を特定する.
主な方法:
- 周期密度関数理論 (DFT) の計算を用いて計算する.
- 金属基板で育ったエピタキシアルグラフェンで原子酸素吸収をシミュレートする.
主要な成果:
- 原子酸化により,安定したグラフェンエノラート中間物質が形成されます.
- エノラートは局所的な最小値であり,グラフェン-金属基板の相互作用によって安定します.
- このエノラートは,これらの条件下でグラフェンエポキシードよりも安定しています.
結論:
- 原子酸化は,グラフェンの機能化のための新しい化学的経路を提供します.
- 安定したグラフェンエノラートは,新しいグラフェンベースのアプリケーションの機会を提供します.
- この中間物質の理解は,グラフェンの化学と材料設計を進める.
関連する概念動画
Hydroboration-Oxidation of Alkenes
In addition to the oxymercuration–demercuration method, which converts the alkenes to alcohols with Markovnikov orientation, a complementary hydroboration-oxidation method yields the anti-Markovnikov product. The hydroboration reaction, discovered in 1959 by H.C. Brown, involves the addition of a B–H bond of borane to an alkene giving an organoborane intermediate. The oxidation of this intermediate with basic hydrogen peroxide forms an alcohol.
Preparation of Epoxides
Overview
Epoxides result from alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
Epoxidation with Peroxy Acids
Epoxidation of alkenes via oxidation with peroxy acids involves the conversion of a carbon–carbon double bond to an epoxide using the oxidizing agent meta-chloroperoxybenzoic acid, commonly known as MCPBA. Since the O–O bond of peroxy acids is very weak, the addition of electrophilic oxygen of peroxy acids to...
Epoxides result from alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
Epoxidation with Peroxy Acids
Epoxidation of alkenes via oxidation with peroxy acids involves the conversion of a carbon–carbon double bond to an epoxide using the oxidizing agent meta-chloroperoxybenzoic acid, commonly known as MCPBA. Since the O–O bond of peroxy acids is very weak, the addition of electrophilic oxygen of peroxy acids to...
Acid-Catalyzed Ring-Opening of Epoxides
Epoxides that are three-membered ring systems are more reactive than other cyclic and acyclic ethers. The high reactivity of epoxides originates from the strain present in the ring. This ring strain acts as a driving force for epoxides to undergo ring-opening reactions either with halogen acids or weak nucleophiles in the presence of mild acid. The acid catalyst converts the epoxide oxygen, a poor leaving group, into an oxonium ion, a better leaving group, making the reaction feasible. The...
Base-Catalyzed Ring-Opening of Epoxides
Due to their highly strained structures, epoxides can readily undergo ring-opening reactions through nucleophilic substitution, either in the presence of an acid or a base. The nucleophilic substitution reactions in the presence of acid are called acid-catalyzed ring-opening reactions, and nucleophilic substitution reactions in the presence of a base are called base-catalyzed ring-opening reactions. Epoxides undergo base-catalyzed ring-opening reactions in the presence of a strong nucleophile...
Reactivity of Enolate Ions
Enolate ions are formed by the acid–base reaction of a carbonyl compound with a base. This leads to deprotonation of the α hydrogen atom, leading to a resonance-stabilized enolate ion where one of the contributing structures is an oxyanion, which imparts additional stability. Therefore, the proton on the α carbon is more acidic in nature than that of other sp3-hybridized C–H bonds but less acidic than those in O–H bonds where the negative charge in the conjugate base is localized on the oxygen...
Regioselective Formation of Enolates
As depicted in the figure below, the unsymmetrical ketones can form two possible enolates: less substituted or more substituted enolates. Usually, the thermodynamic enolates are formed from the more substituted α-carbon atom, while the kinetic enolates are formed faster by deprotonation from the less substituted position. The thermodynamic enolates have lower energy, so they are more stable. But the energy required to form kinetic enolates is less.


