The hexachloroantimonates of cation radicals from 2, 3, 4, 7-8, 9-hexahydro-2, 2, 5.7, 7, 10- hexamethylbenzo [1, 2-b; 4, 5-b'] dipyran (1) and the isomeric benzo [1, 2-b; 4, 3-b'] dipyran (3) have been characterised. The production of cation radical from (1) in acid media is limited by acid concentration for weak acids and also by the presence of oxygen for strong acids. The cation radical species (Ar+) is considered to originate from substrate (Ar) via ...