Allenic bond - Allenic bond

A bond in which three carbon atoms are connected by two adjacent double bonds. The two π orbital planes are perpendicular to each ^other due to the overlap of the p orbital of the central carbon atom with an ^sp hybridized orbital and the p orbitals of the carbon atoms on both ends with ^sp2 hybridized orbitals (Figure). Therefore, molecules with ^R1R2 and ^R3R4 are optically active even though they do not have an asymmetric center (see alternative terminology: molecular asymmetry). Chemically, they show the same reactivity as an ethylene bond.

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

3個の炭素原子が2個の隣接二重結合で結ばれた結合．sp混成軌道をもつ中央の炭素原子とのp軌道と，sp² 混成軌道をもつ両端の炭素原子のp軌道の重なりによって二つのπ軌道面は直交する(図)．したがって，R¹ R²，R³ R⁴ の分子は不斉中心をもたなくても光学活性な分子になる([別用語参照]分子不斉)．化学的には，エチレン結合と同様な反応性を示す．

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