The trimorphism of 3-hydroxybenzoic acid: an experimental and computational study

Abstract

Following the computational prediction that 3-hydroxybenzoic acid (3HBA) could exist in more than the two literature polymorphs, an experimental investigation targeting computationally generated structures was performed. The third polymorphIII, solved from powder X-ray diffraction data, and the literature formIIshare a common hydrogen-bonded ladder motif in contrast to the carboxylic acid dimer based formI. The two metastable polymorphs (IIandIII) are storage stable if phase pure and monotropically related to formI. Calorimetric measurements and (lattice) energy minimisations revealed that the three polymorphs are close in energy.