  Control of molecular orientation is emerging as crucial for the
characterization of the stereodynamics of kinetics processes beyond structural
stereochemistry. The special role played in chiral discrimination phenomena has
been particularly emphasized by the authors after their extensive probes of
experimental control of molecular alignment and orientation. In this work, the
role of the orientation has been demonstrated for the first time in
first-principles molecular dynamics simulations: stationary points
characterized on potential energy surfaces have been calculated for the study
of chemical reactions occurring between the bisulfide anion HS- and oriented
prototypical chiral molecules CHFXY (where X = CH3 or CN and Y = Cl or I). The
important reaction channels are those corresponding to bimolecular nucleophilic
substitution (SN2) and to bimolecular elimination (E2): their relative role has
been assessed and alternative pathways due to the mirror forms of the oriented
chiral molecule are revealed by the different reactivity of the two enantiomers
of CHFCNI in SN2 reaction.
