C4H4O2

The molecular formula C4H4O2 may refer to:


 * Cycloprop-2-ene carboxylic acid
 * Diketene
 * Dioxins
 * 1,2-Dioxin
 * 1,4-Dioxin
 * 2-Furanone
 * Methyl propiolate
 * Tetrolic acid