2,2′-disubstituted 9,9′-spirobifluorene · axial chirality
Axial chirality · point group C₂

2,2′-disubstituted 9,9′-spirobifluorene — the chiral case

Two perpendicular fluorenes meet at the spiro carbon. One substituent on each unit (positions 2 and 2′) makes it chiral (point group C₂). The chirality axis is the spiro axis — the intersection of the two fluorene planes, collinear with the parent S₄. The curved arrow traces the helical sense from the near to the far substituent (P / M). Assignment assumes the 2/2′ group outranks the rest of its fluorene.
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Substituents (2, 2′)
Chirality axis (spiro/S₄)
C₂ symmetry axis (ref.)
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carbon substituent (2× radius) chirality axis (spiro/S₄) C₂ symmetry axis
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