Comparison between the crystal structures of racemic and enantiopure aryl benzyl sulfoxides

In literature reports about the comparison between the crystal structures of racemic and enantiopure compounds, minor differences have been observed between the conformations of an enantiopure compound and the conformations of the same enantiomer when they are a part of a racemic compound. In the present investigation, the crystal structures of aryl benzyl sulfoxides show peculiar behaviours, in particular when the choice between anti or gauche-conformers was investigated. In three cases of poly-halogenated molecules, the most frequent anti-conformations remain for the crystal structures of racemic compounds, whereas the corresponding enantiopure compounds arrange in gauche-conformations. Energy calculations confirm the interactions building up the crystal structures and suggest the reasons for the gauche-anti choice.