  Many molecules exhibit multiple conformers that often easily interconvert
under thermal conditions. Therefore, single conformations are difficult to
isolate which renders the study of their distinct chemical reactivities
challenging. We have recently reported a new experimental method for the
characterization of conformer-specific effects in chemical reactions [Y. P.
Chang et al., Science 342, 98 (2013)]. Different conformers are spatially
separated using inhomogeneous electric fields and reacted with a Coulomb
crystal of cold, spatially localized ions in a trap. As a first application, we
studied reactions between the two conformers of 3-aminophenol and Ca$^+$. We
observed a twofold larger rate constant for the $cis$ compared to the $trans$
conformer which was rationalized in terms of the differences in the long-range
ion-molecule interactions. The present article provides a detailed description
of the new method and a full account of the experimental results as well as the
accompanying theoretical calculations.
