The methoxy-, hydroxy-, and carbonyl-substituted benzenes are the simplest fragments from the lignin separation feedstocks. Extensive experimental thermochemical studies of these compounds were carried out, including combustion calorimetry, vapor pressure measurements, and differential scanning calorimetry. We have collected available primary experimental results on enthalpies of formation and vapor pressures as well as on phase transitions, liquid-gas, liquid-solid, and crystal-liquid. These data were evaluated using empirical, semiempirical, and quantum chemical methods. The consistent sets of evaluated thermodynamic data were used to design the method for predicting enthalpies of vaporization and enthalpies of formation of di- and trisubstituted benzenes. It is expected that parameters and pairwise interactions will be transferable to predict the thermochemical properties of poly methoxy-substituted and poly hydroxysubstituted benzenes that appear in reaction products of lignin transformations in the value-adding chemicals and materials.