A detailed density functional theory examination of the reaction of an iron porphyrin chlorite dismutase model complex with chlorite was performed. We find that the molecular oxygen production observed occurs via the formation of eta(1)-Fe(III) chlorite species, followed by the formation of O=Fe(IV) (compound II) and chlorine monoxide through homolytic bond cleavage. Chlorine monoxide then rebounds to form Fe(III)- peroxyhypochlorite followed by subsequent loss of chloride and loss of dioxygen accompanied by spin conversion to produce the Fe(III) complex and complete the catalytic cycle.