Conformational lability of ibuprofen in supercritical carbon dioxide

A study of conformational equilibria of ibuprofen in vacuum and supercritical carbon dioxide (SC CO2) was carried out using methods of quantum chemistry and molecular dynamics simulation. It was found that ibuprofen forms 12 different conformations in SC CO2, two of them correspond to the structure of the molecule in the crystal lattice of the first and second polymorph. It was shown that the GAFF force field allows one to obtain the characteristics of conformers, almost coinciding with those obtained by quantum chemical calculations at the B3LYP/cc-pVTZ level of theory.