Bromine water, because of the easy oxidation of bromide to the equivalent of Br, a potent electrophile. The enzyme bromoperoxidase catalyzes this reaction. The oceans are estimated to release 1–2 million tons of bromoform and 56,000 tons of bromomethane annually. An old qualitative test for the presence of the alkene functional group is that alkenes turn brown aqueous bromine solutions colourless, forming a bromohydrin with some of the dibromoalkane also produced. The reaction passes through a short-lived strongly electrophilic bromonium intermediate. This is an example of a halogen addition reaction. Bromine is significantly less abundant in the crust than fluorine or
Fluorine perchlorate and perchlorates, it needs to be handled with extreme caution. FClO is a strong oxidant and it reacts with iodide ion: FClO can also react with tetrafluoroethylene: It may be a radical addition reaction. Fluorine perchlorate Perchloryl Hypofluorite is the rarely encountered chemical compound of fluorine, chlorine, and oxygen with the chemical formula or . It is an extremely unstable gas that explodes spontaneously and has a penetrating odor. One synthesis uses fluorine and perchloric acid, though the action of ClF on water is another method. Another method of synthesis involves the thermal decomposition of tetrafluoroammonium perchlorate, , which yields