Effect of pressure on rotational isomers in solution: infrared and Raman spectroscopy

The effect of pressure on the conformational equilibria between rotational isomers in solution has been studied by the infrared and Raman spectroscopy. The experimental volume changes for the transformation are explained theoretically by the three effects contributing to these volume changes, namely the overlap of the atoms with the internal rotation angle, the change of local packing of the solute and solvent, and the change of the electrostatic interaction with the solvent. The purpose of this paper is to review what is known about the volume changes for small molecules with internal rotation angles.