title: C5H4
text: # C5H4
  
  The molecular formula $C_5H_4$ (molar mass: 64.09 g/mol, exact mass: 64.0313 u) may refer to:
  
  * 3-Ethynylcycloprop-1-ene
  * 1,4-Pentadiyne
  * Penta-1,2-dien-4-yne
  * Spiropentadiene, or bowtiediene
  