Density functional computational thermochemistry: Accurate determination of the enthalpy of formation of perfluoropropane from DFT and ab initio calculations on isodesmic reactions

The experimental enthalpy of formation of perfluoropropane (C3F8), reported originally as −1729 kJ/mol and latter corrected to −1784.7 kJ/mol, is reexamined at the light of density functional and model chemistry (G3, CBS-4, CBS-Q) calculations of several isodesmic reactions relating C3F8 to smaller fluoroalkanes. The average enthalpy of formation of C3F8 obtained from all reactions studied was −1739 ± 12 kJ/mol at the DFT level and −1748 ± 12 kJ/mol at the ab initio level, thus ruling out the larger experimental value. A value of −1732 ± 5 kJ/mol is recommended from careful analysis of the theoretical results.