The dehydrogenation reaction of ethane in gallium containing zeolites was studied using density functional theory (DFT) and a non-framework gallium species in the dihydridegallium ion form. Two different mechanisms were considered when examining the dehydrogenation reaction of ethane: a 3-step mechanism and a 1-step concerted mechanism. The activation energy calculated for the concerted mechanism is greater than the one calculated for the 3-step mechanism. In spite of that, due to the major conformational changes involved in the 3-step mechanism, the concerted one could be favored once one considers the effects of the zeolite framework, mainly for larger substrates. (c) 2005 Elsevier B.V. All rights reserved.