The free-radical addition of hydrogen bromide to hexachloromethylenenorbornene affords a 60: 40 mixture of 1-bromomethyl-2, 3, 4, 5, 5, 6-endo-hexachloronorborn-2-ene and 5-endo- bromomethyl-1, 2, 3, 4, 7, 7-hexachloronorborn-2-ene. The aluminium bromide-catalysed ionic addition gives a 68: 32 mixture of 5-exo-bromo-1, 2, 3, 4, 7, 7-hexachloro-5-endo- methylnorborn-2-ene and its 5-endo-bromo-epimer.
