クランクシャフトの動きは,高度に混雑したビス ((triarylmethyl) peroxide) で発生する.
Tinh-Alfredo V Khuong1, Gerardo Zepeda, Carlos N Sanrame
1Department of Chemistry and Biochemistry, University of California-Los Angeles, 405 Hilgard Avenue, Los Angeles, CA 90095-1569, USA.
Journal of the American Chemical Society
|November 13, 2004
まとめ
研究者は,モデル分子,Bis-[tri-(3,5-di-tert-butyl) phenylmethyl]-peroxide 2.でクランクシャフトの動きを調査しました. 核磁共振 (NMR) スペクトロスコーピーは,ローターの内部回転の証拠を提供し,分子レベルでクランクシャフトの動きを確認しました.
科学分野:
- 有機化学 オーガニック・ケミストリー
- 固体化学 固体化学
- スペクトル顕微鏡検査です.
背景:
- クランクシャフトの動きは,内部ローターが円形に回転し,端末ローターが静止する.
- 固体中の分子運動を調査することは,物質の性質を理解するために極めて重要です.
研究 の 目的:
- クランクシャフトの運動を分子レベルで実験的に検証する.
- この運動を研究するためのモデルシステムとしてBis-[tri-(3,5-di-tert-butyl) phenylmethyl]-peroxide 2を使用する.
主な方法:
- 温度変数炭素-13 ((13) C) と陽子 (1H) 核磁共鳴 (NMR) スペクトロスコーピー. 核磁共鳴 (NMR) スペクトロスコーピー.
- 固体 (13) C CPMAS NMRとGIAOの計算. 固体 (13) CPMAS NMRとGIAOの計算. 固体 (13) CPMAS NMRとGIAOの計算. 固体 (13) CPMAS NMRとGIAOの計算. 固体 (13) CPMAS NMRとGIAOの計算.
- 分子力学の計算. 分子力学の計算.
主要な成果:
- クランクシャフトの動きと一致するコンフォームダイナミクスは,ペロキシド2で190〜375Kの間に観察されました.
- NMRのスペクトル割り当ては,2つの異なる凝結プロセスをサポートしました.
- 計算により,クランクシャフトの回転とトリチル群の滑り方を区別した.
結論:
- 実験的証拠は,モデル過酸化物分子のクランクシャフト運動の発生を支持しています.
- この研究は,固体における分子動態を調査するために,NMRスペクトロスコピーと計算方法の使用を検証しています.
関連する概念動画
Regioselectivity of Electrophilic Additions-Peroxide Effect
In the presence of organic peroxides, the addition of hydrogen bromide to an alkene yields the isomer that is not predicted by Markovnikov’s rule. For example, the addition of hydrogen bromide to 2-methylpropene in the presence of peroxides gives 1-bromo-2-methylpropane. This addition reaction proceeds via a free radical mechanism, which reverses the regioselectivity. The free radical reaction mechanism involves three stages: initiation, propagation, and termination.
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.
Alkynes 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.
Woodward–Hoffmann Selection Rules and Microscopic Reversibility
Electrocyclic reactions, cycloadditions, and sigmatropic rearrangements are concerted pericyclic reactions that proceed via a cyclic transition state. These reactions are stereospecific and regioselective. The stereochemistry of the products depends on the symmetry characteristics of the interacting orbitals and the reaction conditions. Accordingly, pericyclic reactions are classified as either symmetry-allowed or symmetry-forbidden. Woodward and Hoffmann presented the selection criteria for...
ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH3
All ortho–para directors, excluding halogens, are activating groups. These groups donate electrons to the ring, making the ring carbons electron-rich. Consequently, the reactivity of the aromatic ring towards electrophilic substitution increases. For instance, the nitration of anisole is about 10,000 times faster than the nitration of benzene. The electron-donating effect of the methoxy group in anisole activates the ortho and para positions on the ring and stabilizes the corresponding...
Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)
Ring-opening metathesis polymerization or ROMP involves strained cycloalkenes as starting materials. The mechanism of ROMP proceeds by reacting cycloalkene with Grubbs catalyst to give metallacyclobutane intermediate which undergoes a ring-opening reaction to form new carbene. The new carbene reacts with another molecule of cycloalkene. Repetition of these steps leads to the formation of an unsaturated open-chain polymer product. All these steps are reversible, however, relieving the ring...
![Mizoroki-Heck Cross-coupling Reactions Catalyzed by Dichloro{bis[1,1',1''-(phosphinetriyl)tripiperidine]}palladium Under Mild Reaction Conditions](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F51444.jpg&w=3840&q=50)

