Hosta

Cyclopropatriene is a hypothetical compound (C₃) which is an allotrope of carbon. It was once proposed as a candidate for a spectroscopically observed tricarbon species. It is a cyclic cumulene.^[1]

References

^ Rogers, Donald W.; McLafferty, Frank (1995). "G2 Ab Initio Calculations of the Enthalpies of Formation of C₃ Hydrocarbons". The Journal of Physical Chemistry. 99 (5): 1375. doi:10.1021/j100005a002.

Allotropes of carbon
sp³ forms	Diamond (cubic) Lonsdaleite (hexagonal diamond)
sp² forms	Graphite Graphene Fullerenes, including C₆₀ (buckminsterfullerene), C₇₀, Fullerene whiskers, Nanotubes, Nanobuds, Nanoscrolls) Glassy carbon
sp forms	Linear acetylenic carbon C ₁₈ (cyclo[18]carbon)
mixed sp³/sp² forms	Amorphous carbon Carbon nanofoam Carbide-derived carbon Q-carbon
other forms	C ₁ (atomic carbon) C ₂ (diatomic carbon) C ₃ (tricarbon)
hypothetical forms	C ₃ (cyclopropatriene) C ₆ (benzotriyne) C ₆ (prismane C8) Chaoite Haeckelites Cubic carbon Metallic carbon Penta-graphene
related	Activated carbon Carbon black Charcoal Carbon fiber Aggregated diamond nanorod