Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)The goal of this paper is proposing a simple molecular descriptor, based on the molecular structures, for predicting the normal boiling temperature (B.T.) of hydrocarbons. To this end, the topological index Fi was developed and used to correlate the topology of alkanes, alkenes, alkynes and cycloalkanes possessing normal or branched chains to their B.T. The robustness of predictor Fi was evaluated by comparison with the most cited predictors in the literature: Weiner, Hosoya and Randle. The quadratic model developed in this work predicts very well the B.T. of hydrocarbons. In the first moment, the developed model was tested for predicting the B.T. of alkanes. After, it was applied with success for predicting the B.T. of other compounds (alkenes, alkynes and cycloalkanes). The topological index Fi proved to be rather effective and produced small deviations, as compared to other topological indexes used for comparison. Based on the topological index Fi, other properties of interest can also be further explored and the concepts developed in this work can be easily adapted to other families of compounds, mainly in liquid phase. (C) 2011 Elsevier B.V. All rights reserved.165125132Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)