When evaluating electric field effects, the 100 conformers obtained in the absence of a field were re-optimized, and subsequently re-ranked, in the presence of one, at DFT level of theory. As already indicated in the introduction, this rigorousand computationally expensive -treatment of conformer space turned out to be essential in our analysis: for many species, we observed that the conformer ranking changes dramatically upon turning on the OEEF. Conformers that in the absence of a field don't even appear in the top 20 can all of a sudden become the lowest energy conformer when an electric field is taken into account (see Figure for a representative example). As such, the traditional computational approach to evaluate electric field effects by focusing on the stabilization of the lowest energy conformer for every species identified along the reaction profile in the absence of an electric field would have induced significant errors in the presented results.