C4H4O2
# 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
