Molecular structure and polymorphism of a cyclohexanediol: trans-1,4-cyclohexanedimethanol

摘要

This study aims to investigate the molecular structure and polymorphism of trans-1,4-cyclohexanedimethanol,including the bi-axial/bi-equatorial equilibrium and the nature of the intermolecular H-bond networks incondensed phases created by the hydroxyl group torsions. The full conformational space of the singlemolecule was explored by MP2 calculations, showing that the optimized bi-equatorial conformers havesimilar stability and the bi-axial ones have much higher energies. The hydroxymethyl substituents havepreference for gauche/anti or gauche+/gauche− conformations. Polymorphic forms were generated bycrystallization from solutions and by cooling the melt, which were characterized by a combination oftechniques: DSC, PLTM and XRD. Two polymorphs were isolated and their crystal structures were solvedby direct methods based on single-crystal X-ray analysis. Both were found to contain two of the moststable conformers found in the computational calculations. The influence of H-bonding in the polymorphicstructures was verified by analysis of the structural differences between the geometries present inthe polymorphs determined by XRD and their single molecule counterparts resulting from the theoreticalcalculations. The bi-axial conformations are destabilized over the bi-equatorial ones in isolated andcrystalline forms of trans-1,4-cyclohexanedimethanol.