Phase transitions in some hydrogen-bonded molecules

The calorimetric parameters including the heat capacity, thermal conductivity and thermal diffusivity are measured and/or deter-mined as a function of temperature (310 K < T < 400 K) for two hydrogen-bonded molecules, namely anthralinic acid C6H4COOHNH2 and p-nitrophenol C6H4NO2OH. It seems likely that the first compound undergoes a structural phase transition around 354 K whereas for the second compound the transition temperature is 336 K. Furthermore, the order of magnitude of the above-mentioned parameters suggests that the two compounds under current investigation behave as poorly conducting materials. The thermogravimetric analysis (TGA) for the two compounds was carried out. An interpretation of our data has been outlined on the basis of the crystal structure including the arrangement of the hydrogen bonding system in each compound.