3-Methylenecyclopropene, also called Methylenecyclopropene or Triafulvene, is a hydrocarbon with chemical formula C4H4. It is a colourless gas that polymerizes readily as a liquid or in solution but is stable as a gas. This highly strained and reactive molecule was synthesized and characterized for the first time in 1984, and has been the subject of considerable experimental and theoretical interest. It is an example of a cross-conjugated alkene, being composed of cyclopropene with an exocyclic double bond attached.

CAS：4095-06-1
中文别名：
英文别名：Triafulvene;Cyclopropene,methylene-(7CI,8CI,9CI);Methylenecyclopropene;3-methylene-cyclopropene;Cyclopropene,3-methylene;
分子式：C4H4
分子量：52.0746
精确质量：52.0313
Psa：0.0
Logp：1.1124

密度：0.82g/cm3
沸点：26ºC at 760mmHg
折射率：1.481