Methoxy-substituted benzenes are the simplest fragments from the lignin separation feedstock. Extensive experimental thermochemical studies of these compounds were carried out, including vapor pressure measurements, combustion and differential scanning calorimetry. These data were evaluated using empirical, semi-empirical and quantum chemical methods. The consistent sets of evaluated thermodynamic data were used to design the method for predicting enthalpies of vaporisation and enthalpies of formation of di- and tri-substituted benzenes. It has been found that the agglomeration of substituents on the benzene ring has dramatic consequences for the energetics of the molecule (in terms of the enthalpy of formation), as well as for the energetics of intermolecular interactions (in terms of the enthalpy of vaporisation). These observations are essential to reliably assess the energetics of the molecules that appear in reaction products of lignin transformations in value-adding chemicals and materials.
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