Calculation of Heat of Formation for Tensile Cyclic Molecules in Condensed Phase Using Electrostatic Potential and QSPR Schemes

Abstract

PDDG/PM3 method was evaluated as a suitable semiempirical calculation for heat of formation of tensile cyclic organic molecules in gas phase and used in subsequent researches. In order to compute the heat of formation of these compounds in condensed phase, electrostatic potential scheme was performed to obtain the area of the Bader surface at B3LYP/6-311G** level. The root mean square (rms) of the calculated condensed phase heat of formation for 58 molecules from corresponding experimental values is 4.81 kcal/mol. Six QSPR schemes for predicting solid phase heat of formation of 38 model molecules with physically meaningful descriptors from genetic algorithm selection were established. These selected descriptors were recalculated by DFT B3LYP/6-311G** and MP2/6-311G** methods, which could then give similar and better results. The QSPR schemes adopted back-propagation neutral network (BPNN) and support vector machine (SVM) as analysis tools. It was suggested that selection of descriptors with strong physical significance in QSPR calculation should be important.