4-ヒドロキシベンゼンダイアゾニウム塩と反応する単一壁の炭素ナノチューブの構造-反応性の関係
Nitish Nair1, Woo-Jae Kim, Monica L Usrey
1Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
Journal of the American Chemical Society
|March 14, 2007
まとめ
研究者は,単一壁の炭素ナノチューブ (SWNTs) の電子伝送のための構造反応性モデルを開発しました. 照明は選択性を低下させ,半導体よりも金属SWNTによる反応を好む.
科学分野:
- 材料科学 材料科学とは
- ナノテクノロジー ナノテクノロジー
- 物理化学 物理化学
背景:
- 電子伝送反応は,単一壁の炭素ナノチューブ (SWNTs) の機能化に不可欠です.
- 構造と反応性の関係を理解することは,SWNTの電子特性を制御する鍵です.
- 以前の研究では,SWNTの電子伝送選択性に関する定量モデルが欠けていた.
研究 の 目的:
- SWNTの電子移転反応における最初の構造-反応性関係を導き出し,検証する.
- SWNTにおける電子的に選択的な反応のメカニズム的基礎を解明する.
- 反応選択性に対する照明などの外部要因の影響を調査する.
主な方法:
- モデル電子受容体として4-ヒドロキシベンゼンダイアゾニウムを使用した.
- 安定状態の反応データに対する吸収制御スキームに基づくモデルを開発した.
- ナノチューブキラリティの反応性の違いを説明するために,電子伝送理論を応用した.
- 反応中のUV対nIR吸収スペクトルの変化を定量的に分析した.
主要な成果:
- SWNT電子移転の検証された構造-反応性関係を確立しました.
- 半導体SWNTよりも金属SWNTの反応剤選択性を照明が著しく低下させることが実証されました.
- 照明下での溶液中の反応剤の反応性の増加が観察されました.
- 反応中のSWNTのスペクトル変化の定量的な記述を提供した.
結論:
- 開発されたモデルは,SWNTに対する電子的に選択的な反応に関する機械的洞察を提供します.
- 照明は電子伝送反応の選択性を変化させ,SWNTの機能化に影響を与えます.
- この発見は,SWNTの電子特性に基づいて制御された化学的改変を設計する上で極めて重要です.
さらに関連する動画
関連する概念動画
01:07Structure 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.
01:18Structure of Benzene: Molecular Orbital Model
According to the molecular orbital (MO) model, benzene has a planar structure with a regular hexagon of six sp2 hybridized carbons. As shown in Figure 1, each carbon is bonded to three other atoms with C–C–C and H–C–C bond angles of 120°. The C–H bond length is 109 pm, and the C–C bond length is 139 pm which is midway between the single bond length of sp3 hybridized carbons (154 pm) and sp2 hybridized carbons (133 pm).
01:11Nucleophilic Aromatic Substitution: Elimination–Addition
Simple aryl halides do not react with nucleophiles. However, nucleophilic aromatic substitutions can be forced under certain conditions, such as high temperatures or strong bases. The mechanism of substitution under such conditions involves the highly unstable and reactive benzyne intermediate. Benzyne contains equivalent carbon centers at both ends of the triple bond, each of which is equally susceptible to nucleophilic attack. This 50–50 distribution of products is confirmed through isotopic...
01:14Nucleophilic Aromatic Substitution of Aryldiazonium Salts: Aromatic SN1
Treating arylamines with nitrous acid gives aryldiazonium salts that are effective substrates in nucleophilic aromatic substitution reactions. The diazonio group in these salts can be easily displaced by different nucleophiles, yielding a wide variety of substituted benzenes. The leaving group departs as nitrogen gas, and this easy elimination is the driving force for the substitution reaction.
In the Sandmeyer reaction, for example, the diazonio group is replaced by a chloro, bromo, or cyano...
In the Sandmeyer reaction, for example, the diazonio group is replaced by a chloro, bromo, or cyano...
01:20Diazonium Group Substitution with Halogens and Cyanide: Sandmeyer and Schiemann Reactions
Arenediazonium substitution reactions occur when the diazonium group is substituted by various functional groups such as halides, hydroxyl, nitrile, etc. For instance, arenediazonium salts react with copper(I) salts of chloride, bromide, or cyanide to form corresponding aryl chlorides, bromides, and nitriles. These reactions are named Sandmeyer reactions. Although the mechanism of this reaction is complicated, as illustrated in Figure 1, they are believed to progress via an aryl copper...
01:371° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Mechanism
Nitrous acid is a relatively weak and unstable acid prepared in situ by the reaction of sodium nitrite and cold, dilute hydrochloric acid. In an acidic solution, the nitrous acid undergoes protonation when it loses water to form a nitrosonium ion—an electrophile. Nitrous acid reacts with primary amines to give diazonium salts. The reaction is called diazotization of primary amines.