This study was carried out to show the predictive capacity of the semi-empirical topological index (I ET ) in estimating some important physical properties; melting point, Mp (-C), boiling point, Bp (-C), and experimental log p of halogenated aliphatic hydrocarbons. The retention index (RI) values of 141 compounds were used in the building of this specific model of the I ET . The simple linear regression between RI Exp and the I ET exhibits high quality with a coefficient of determination of r 2 ¼ 0.9995, standard deviation of SD ¼ 8 and leave-one-out cross-validation correlation coefficient of r Finally, for 19 compounds the correlation between the experimental log p-value and that calculated using the I ET method gave a value of r 2 ¼ 0.9871, while the correlation with the value obtained using the most used Fragment Addition Method was r 2 ¼ 0.9750. These results show the predictive capacity of the I ET for these physical properties.

The semi-empirical topological index (I(ET)), developed to predict the chromatographic retention of a series of organic compounds, is extended to predict other properties and biological activities of aliphatic alcohols. This topological index takes into account the contribution of each individual atom type to the property considered and is able to encode information about structural features of the molecules. The efficiency of this index is verified by high quality Structure - Property and structure - Activity Relationships (QSPR/QSAR) models obtained for several representative physicochemical properties, biological activities and toxicities of aliphatic alcohols. Most of the properties investigated are well modeled (r > 0.98) employing the I(ET). Cross-validation using the more general leave-one-out method demonstrates that these models are highly statistically reliable. The proposed I(ET) index promises to be a useful descriptor in the QSPR/QSAR studies.

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