When theory and experiment hold hands: The thermochemistry of γ-pyrone derivatives

In this work, we have determined the experimental standard ( ^p=0.1MPa) molar enthalpies of formation, in the gas phase, of 2,6-dimethyl-4-pyrone -(261.5 ± 2.6) kJ · mol^-1 and 2-ethyl-3-hydroxy-4-pyrone -(420.9 ± 2.8) kJ · mol^-1. These values were obtained by combining the standard molar enthalpy of formation in the condensed phase, derived from combustion experiments in oxygen, at T = 298.15 K, in a static bomb calorimeter, with the standard molar enthalpy of sublimation, at T = 298.15 K, obtained by Calvet microcalorimetry. Additionally, high-level density functional theory calculations using the B3LYP hybrid exchange-correlation energy functional with extended basis sets have been performed for these two compounds. Good agreement was obtained between the experimental and computational results. Using the same methodology, we calculated the standard molar enthalpy of formation of gaseous 2-methyl-3-hydroxy-4-pyrone.