Energetic characterization of indanone derivatives involved in biomass degradation

The energetic study of 6-methyl-1-indanone, 6-methoxy-1-indanone and 5,6-dimethoxy-1-indanone has been developed using calorimetric techniques and a computational methodology. The enthalpies of combustion and of sublimation of these compounds were determined from, respectively, static-bomb combustion calorimetry and high-temperature Calvet microcalorimetry. From these experimental data, the gas-phase standard molar enthalpies of formation were derived. Also, the temperature and the enthalpy of fusion of each compound were obtained by differential scanning calorimetry. Additionally, the gas-phase standard molar enthalpies of formation of these compounds were obtained from high-level ab initio calculations, at the G3(MP2)//B3LYP level of theory. The computational approach of these three indanone derivatives allowed us to establish their molecular structures, the co-existence of two and four stable conformations for 6-methoxy-1-indanone and 5,6-dimethoxy-1-indanone, respectively. Furthermore, the energetic effects associated with the presence of one methyl group and one or two methoxy groups in the indanone structure were evaluated. These enthalpic increments were compared with the homologous substitutions in the benzene and naphthalene molecules.