The influence of the hydroxy and methoxy functional groups on the energetic and structural properties of naphthaldehyde as evaluated by both experimental and computational methods

This work addresses an energetic and structural study regarding hydroxy and methoxy naphthaldehyde derivatives, based both on experimental and computational research. The massic energy of combustion and vapor pressures at different temperatures were measured by static-bomb combustion calorimetry and Knudsen mass-loss effusion techniques, respectively. The computational studies were performed using the G3(MP2)//B3LYP method, an appropriate theoretical procedure for these kinds of compounds. The combination of experimental and computational data enabled the determination of the enthalpies, entropies, and Gibbs energies of sublimation and formation of these compounds both in the crystal and gas phase. Complementing the experimental studies, the intramolecular hydrogen bonding energetics of all three o-hydroxynaphthaldehydes and their corresponding tautomeric structures were evaluated. Additionally, the gasphase Gibbs free energy and enthalpy of formation of the radical and anion as well as the O–H homolytic bond dissociation enthalpy and gas-phase acidity were studied.