Comparative study on the gas-phase heats of formation

초록

Prediction of various physicochemical properties of not-yet-synthesized molecules is a prerequisite for further development of new molecules. Heat of formation is an important property for this purpose. When experimental data is not available, the best way is to compute energy (and enthalpy) using computational packages. Politzer and coworkers estimated heats of formation of organic molecules using BP86/6-31G(d,p) optimized structures and some correction terms involving hybridization states of atoms. The average absolute error (AAE) and standard deviation (SD) were 3 and 4 kcal/mol, respectively. Here, we developed parameters for low-cost computational methods - B3LYP/6-31G(d), AM1 and PM3. We obtained better results for R2 and SD (0.995 and 2.8 kcal/mol) using B3LYP parameters. Among semi-empirical methods, parameters derived from PM3 can be applied to a routine work for fast prediction of heats of formation of unknown molecules.