On molecular polarizability. 4. Evaluation of the ionization potential for alkanes and alkenes with polarizability.

To express the influence of polarizability effect on ionization potential (Ip), the Geometric Mean Polarizability Effect Index (GMPEI) and Geometric Mean Polarizability Effect Index of pi Bond (GMPEIpi) were proposed for alkanes and alkenes, respectively. Taking a few of the compounds as a model, we obtained the correlation equations between the experimental Ip and GMPEI or GMPEI pi and then, with the obtained equations, we evaluated the Ip for the title compounds. The estimated Ip values by this work are in good agreement with the measured ones. Furthermore, the ab initio (#HF/6-31G** OPT, Gaussian 98 program) and semiempirical (AM1) Ip computation are finished, and other topological index correlations with the Ip of alkane are discussed.