Thermodynamic and structural aspects of hydroxybenzamide molecular crystals study

Temperature dependencies of vapor pressure were obtained by flow inert gas-carrier transfer method for 2-, 3- and 4-hydroxybenzamide in the temperature interval (from 302.15 to 345.15) K, (from 367.65 to 396.15) K and (from 360.15 to 420.65) K, respectively. The thermodynamic functions of sublimation process were estimated on the basis of the experimental results. The fusion processes of the compounds under investigation were studied using the differential scanning calorimetry method. The comparative analysis of parameters describing packing density of molecules in crystal lattices was done and thermodynamic and thermophysical parameters of sublimation and fusion processes were analyzed. The influence of crystal density calculated based on the X-ray data on sublimation enthalpy under standard conditions was found. For some benzamide derivatives the sublimation enthalpy was observed to depend on the melting point temperature.

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► Thermodynamic characteristics of sublimation process have been calculated for 2-, 3-, 4-hydroxybenzamides.
► The correlation between sublimation thermodynamic functions and parameter describing the molecule packing density in the crystal lattices was obtained.
► The sublimation enthalpy increases with a gain in density of the isomers.