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Updated: Jan 18, 2026

Isolating Free Carbenes, their Mixed Dimers and Organic Radicals
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[6]サイクロ・パラ・フェニルメチン:ベンゼンのアナログで,全般的な芳香性と開いた殻のダイラジカル特性を示す

Zhengtao Li1, Tullimilli Y Gopalakrishna1, Yi Han1

  • 1Department of Chemistry , National University of Singapore , 3 Science Drive 3 , 117543 , Singapore.

Journal of the American Chemical Society
|October 1, 2019
PubMed
まとめ

私たちは,ベンゼンのような性質とダイラジカルな性質を示す [6]サイクロパラフェニルメチン ([6]CPPM) マクロサイクルを合成しました. この"スーパーベンゼン"は ニュートラル状態とディケーション状態で グローバルな芳香性と ユニークな電子的振る舞いを示しています

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Neutral hydrocarbons like cyclopentadiene with an odd number of carbon atoms and one intervening CH2 group in the ring are not aromatic. Cyclopentadiene with 4 π electrons does not satisfy the 4n + 2 π electron rule. Additionally, the intervening CH2 group is sp3 hybridized and lacks a vacant p orbital, thereby interrupting the overlap of p orbitals in a continuous manner and preventing the delocalization of π electrons throughout the ring.
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Cycloheptatriene is a neutral monocyclic unsaturated hydrocarbon that consists of an odd number of carbon atoms and an intervening sp3 carbon in the ring. The three double bonds in the ring correspond to 6 π electrons, which is a Huckel number, and therefore satisfies the criteria of 4n + 2 π electrons. However, the intervening sp3 carbon disrupts the continuous overlap of p orbitals. As a result, cycloheptatriene is not aromatic.
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Like benzene, cyclobutadiene and cyclooctatetraene are cyclic compounds with alternate single and double bonds. However, their chemical behavior differs from benzene, as they are unstable and not aromatic. So, what are the structural characteristics of unsaturated compounds categorized as aromatic?  
For the first time, Eric Hückel, a German chemical physicist, derived a set of structural features for a compound to be classified as aromatic. This is now known as Hückel’s rule or the 4n +...
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