Circumtrindene, a C36H12 open geodesic dome with alternating five- and six-membered rings, is of interest as a vesicle for carrying out chemical reactions and also as a model for certain carbon nanotube caps. Here the addition of an oxygen atom to circumtrindene is examined by means of density functional calculations. O-atom addition to a C-C bond shared between the central and adjacent hexagons gives an epoxide structure while O-atom addition to a C-C bond shared by the central hexagon and an adjacent pentagon results in cleavage of the C-C bond and an R-O-R insertion product. Despite their structural dissimilarity, the two oxidation products are predicted to be of comparable stability (with binding energies of -74.9 and -78.7 kcal/mol, respectively), and to have a large (55.7 kcal/mol) barrier for interconversion.