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Updated: Jun 4, 2026
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Isolating Free Carbenes, their Mixed Dimers and Organic Radicals
Published on: April 19, 2019
カーベンの安定性:シングレットとトリプルットの独立した測定
Scott Gronert1, James R Keeffe, Rory A More O'Ferrall
1Department of Chemistry, Virginia Commonwealth University, 1001 W. Main Street, Richmond, Virginia 23284, United States. sgronert@vcu.edu
Journal of the American Chemical Society
|February 24, 2011
まとめ
この研究では,水素化エンタルピーを使用してカルベンの熱力学的安定性を定量化し,各種のカルベンのシングレット-トリプレットギャップと安定性スケールとの相関関係を明らかにしました.
科学分野:
- コンピューティング・ケミストリー
- 量子化学とは,量子化学である.
- 有機化学 オーガニック・ケミストリー
背景:
- カーベンは,有機合成において極めて重要な反応性中間物質である.
- 熱力学的安定性を理解することは,反応性を予測する鍵です.
- 既存の安定性スケールは,さまざまなカルベンの構造を完全に捉えることができないかもしれません.
研究 の 目的:
- 92種類のカルベンの熱力学的安定性を評価するために (シングレットとトリプルツ).
- シングレットとトリプルツのための新しいカルベン安定化エンタルピー (CSE) スケールを開発する.
- 構造と安定性の関係を調査し,循環カルベンの芳香度を推定する.
主な方法:
- 水素化エンタルピーは,G3MP2の理論レベルを使用して計算されました.
- シングレット・トライレット・ギャップと水素化エンタルピーとの相関の分析.
- シングレットカルベンとトリプルレットカルベンのCSEスケールの開発.
主要な成果:
- シングレット-トリプレットギャップとシングレット水素化エンタルピーとの間には,顕著な異常値を持つ良好な相関が観察されました.
- 新しいCSEスケールが確立され,カルベンの安定性に対する構造的影響を強調した.
- イミダゾル-2-イリデンは,約20kcal/molの芳香的安定エネルギーを持っていると推定されました.
結論:
- 水素化エンタルピーは,カルベンの熱力学的安定性を評価するための信頼できる方法を提供します.
- 開発されたCSEスケールは,シングレットカルベンの安定性やトリプレートカルベンの安定性についての洞察を提供します.
- この研究は,芳香度を含むカルベンの性質を評価するための計算方法の有用性を実証しています.
関連する概念動画
01:59Relative Stabilities of Alkenes
The relative stability of alkenes can be determined by comparing their heats of hydrogenation. The lower heat of hydrogenation indicates the more stable alkene. The three main factors determining the relative stability of alkenes are i) the number of substituents attached to the double-bond carbon atoms, ii) hyperconjugation, and iii) the stereochemistry of the double bond.
01:28Stability of Conjugated Dienes
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A comparison of the enthalpies of hydrogenation of dienes reveals that conjugated dienes release less heat on hydrogenation, rendering them more stable than their nonconjugated analogs.
A comparison of the enthalpies of hydrogenation of dienes reveals that conjugated dienes release less heat on hydrogenation, rendering them more stable than their nonconjugated analogs.
01:07Radicals: Electronic Structure and Geometry
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Accordingly, the structure of a trivalent radical lies between the geometries of carbocations and carbanions. An sp2-hybridized carbocation is trigonal planar, while an sp3-hybridized carbanion is trigonal pyramidal. Here, the difference in geometry is...
Accordingly, the structure of a trivalent radical lies between the geometries of carbocations and carbanions. An sp2-hybridized carbocation is trigonal planar, while an sp3-hybridized carbanion is trigonal pyramidal. Here, the difference in geometry is...
01:24π Molecular Orbitals of 1,3-Butadiene
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The simplest conjugated diene is 1,3-butadiene: a four-carbon system where each carbon is sp2-hybridized and has an unhybridized p orbital that contains an unpaired electron. According to molecular orbital theory, atomic orbitals combine to form molecular orbitals such that the number...
The simplest conjugated diene is 1,3-butadiene: a four-carbon system where each carbon is sp2-hybridized and has an unhybridized p orbital that contains an unpaired electron. According to molecular orbital theory, atomic orbitals combine to form molecular orbitals such that the number...
02:30Stability of Substituted Cyclohexanes
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The two chair conformations of cyclohexanes undergo rapid interconversion at room temperature. Both forms have identical energies and stabilities, each comprising equal amounts of the equilibrium mixture. Replacing a hydrogen atom with a functional group makes the two conformations energetically non-equivalent.
For example, in...
The two chair conformations of cyclohexanes undergo rapid interconversion at room temperature. Both forms have identical energies and stabilities, each comprising equal amounts of the equilibrium mixture. Replacing a hydrogen atom with a functional group makes the two conformations energetically non-equivalent.
For example, in...
01:18Frost Circles for Different Conjugated Systems
The inscribed polygon method is consistent with Hückel’s 4n + 2 rule and helps to learn whether the given cyclic compound is aromatic or not. The compound is stable and aromatic if every bonding molecular orbital (MO) is completely filled with a pair of electrons. However, if the non-bonding or antibonding orbitals are filled with electrons, the compound is unstable and not aromatic. Consider the Frost circle diagrams for cycloalkenes containing 4 to 8 carbons.