Semi‐empirical topological index to predict properties of halogenated aliphatic compounds

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  = 0.9995, standard deviation of SD = 8 and leave‐one‐out cross‐validation correlation coefficient of $r_{{\bf cv}}^2 $  = 0.999. The best correlations between experimental melting, Mp (°C), and boiling Bp (°C) points, and I ET were achieved through quadratic polynomial equations. The correlation of Bp (°C) with I ET for 86 compounds showed excellent results: r 2  = 0.9971, SD = 4.2, $r_{{\bf cv}}^2 $  = 0.997. From this equation the values of 24 compounds not included in the model were calculated ( r 2  = 0.9931; SD = 7.6). The correlation between Mp (°C) and I ET for 43 compounds was very good ( r 2  = 0.9865; SD = 6.1; $r_{{\bf cv}}^2 $  = 0.985), and experimental values of eight compounds not included in the initial model also showed good correlation with calculated values ( r 2  = 0.9903; SD = 4.1). 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  = 0.9871, while the correlation with the value obtained using the most used Fragment Addition Method was r 2   =  0.9750. These results show the predictive capacity of the I ET for these physical properties. Copyright © 2008 John Wiley & Sons, Ltd.