Solid and Solution State Thermodynamics of Polymorphs of Butamben (Butyl 4-Aminobenzoate) in Pure Organic Solvents.

The solubility of butamben has been measured gravimetrically in pure methanol, 1-propanol, 2-propanol, 1-butanol, and toluene over the temperature range 268-298 K. Polymorph transition and melting temperatures, associated enthalpy changes, and the heat capacity of the solid forms and the supercooled melt have been measured by differential scanning calorimetry. Based on extrapolated calorimetric data, the Gibbs energy, enthalpy and entropy of fusion, and the activity of solid butamben (the ideal solubility) have been calculated from below ambient temperature up to the melting point.

Thermodynamic Stability Analysis of Tolbutamide Polymorphs and Solubility in Organic Solvents.

Melting temperatures and enthalpies of fusion have been determined by differential scanning calorimetry (DSC) for 2 polymorphs of the drug tolbutamide: FI(H) and FV. Heat capacities have been determined by temperature-modulated DSC for 4 polymorphs: FI(L), FI(H), FII, FV, and for the supercooled melt. The enthalpy of fusion of FII at its melting point has been estimated from the enthalpy of transition of FII into FI(H) through a thermodynamic cycle.