1,2-dioxin

1,2-Dioxin is a heterocyclic, organic, antiaromatic compound with the chemical formula CHO. It is an isomeric form of 1,4-dioxin (or p-dioxin). thumb|left|1,2-Dioxin (left) and 1,4-dioxin (right)

Due to its peroxide-like characteristics, 1,2-dioxin is very unstable and has not been isolated. Calculations suggest that it would isomerize rapidly into but-2-enedial. Even substituted derivatives, such as 1,4-diphenyl-2,3-benzodioxin, are very labile. thumb|left|Structure of the transient 1,4-diphenyl-2,3-benzodioxin