We address the mechanism responsible for the chirality-selective destruction of carbon nanotubes upon oxidation. The reaction barriers for breaking the C-C bonds of carbon nanotubes are obtained based on density functional calculations. The barrier height is associated with the local-curvature radii along with the breaking C-C bonds rather than the diameters of nanotubes. Furthermore, hole doping can alter the order of the reaction barrier heights. These findings can be utilized for the chirality selection of nanotubes using oxidative purification. (C) 2008 Elsevier B.V. All rights reserved.