Fullerenol is one of the main precursors of fullerene-based materials, which is promising for various biological applications because of its unusual biocompatibility and biofunctionality. However, the functional groups, acidity and reducibility, which substantialize the applications of fullerenols, remain open questions. Using density functional theory calculations, we investigated reaction mechanisms underlying the acidity and reducibility of C60 fullerenols. On the basis of theoretical insights combined with synthesis, IR and NMR structural characterization of 13C-labeled C60 fullerenols, we identified the functional groups and developed and verified a structural model for C60 fullerenols. The results show a strong dependence of acidity and reducibility on the hydroxyl distributions of fullerenols. Fullerenols with stable [small pi]-electron configurations on C60 cores, in which no double bonds have to be placed in conjugated pentagonal rings when drawing their Kekule structures, have low acidities a