title: C4H4O2
text: # C4H4O2
  
  The molecular formula $C_4H_4O_2$ may refer to:
  
  * Cycloprop-2-ene carboxylic acid
  * Diketene
  * Dioxins
     * 1,2-Dioxin
     * 1,4-Dioxin
  * 2-Furanone
  * Methyl propiolate
  * Tetrolic acid
  