Dissociation and isomerization channels of C2H7+ and C3H9+ have been globally explored by the scaled hypersphere search (SHS) method, which discloses reaction routes in an automatic way by following the anharmonic downward distortion on the potential energy surfaces. New structures have been discovered in addition to all of reported ones. Branching ratios leading to C2H(5)(+) + CH4 -> C3H9+ -> C3H7+ + H-2 have been calculated based on microcanonical rate constants of all transition state structures elucidated by the SHS method. Generation of cyclic C3H7+ has been predicted to be responsible for this reaction in a certain collision energy range. (c) 2007 Elsevier B.V. All rights reserved.