Here we introduce a new topological approach which provides a good model for the stability of linear and branched alkanes as well as the strain energy of cycloalkanes. We find that the ratio of 1,3-interactions with respect to the total number of 1,2-, 1,3- and 1,4-interactions plays a fundamental stabilizing role in the energetic of alkanes. These stabilizing effects are larger in branched than in linear alkanes. The heat of formation of alkanes can be obtained as a combination of stabilizing effects coming from atoms, bonds and protobranches. (C) 2008 Elsevier B. V. All rights reserved.