Journal Article

Specific Chemical Reactivities of Spatially Separated 3-Aminophenol Conformers with Cold Ca + Ions

Wild, Dieter, Willitsch, Stefan, Rösch, Daniel, Chang, Yuan-Pin, Długołęcki, Karol, Küpper, Jochen

2013

Overview

Most molecules manifest a fair amount of flexibility at room temperature, in particular through interconversion of rotational conformers—structures that differ by the relative orientation of groups on either side of a single covalent bond. Chang et al. (p. 98 ; see the Perspective by Heaven ) devised a method to explore the comparative reactivities of different conformers. A mixture of the conformers was prepared in a molecular beam cold enough to preclude interconversion; then an electric field was used to push the different conformers apart, spatially resolving subsequent collisional interactions with a target of trapped ions. A molecular beam technique measures the different reactivities of a compound’s distinct rotational conformations. [Also see Perspective by Heaven ] Many molecules exhibit multiple rotational isomers (conformers) that interconvert thermally and are difficult to isolate. Consequently, a precise characterization of their role in chemical reactions has proven challenging. We have probed the reactivity of specific conformers by using an experimental technique based on their spatial separation in a molecular beam by electrostatic deflection. The separated conformers react with a target of Coulomb-crystallized ions in a trap. In the reaction of Ca + with 3-aminophenol, we find a twofold larger rate constant for the cis compared with the trans conformer (differentiated by the O–H bond orientation). This result is explained by conformer-specific differences in the long-range ion-molecule interaction potentials. Our approach demonstrates the possibility of controlling reactivity through selection of conformational states.

• Publisher: American Association for the Advancement of Science,The American Association for the Advancement of Science
• Subject: ambient temperature / aminophenols / Bibliometrics. Scientometrics / Bibliometrics. Scientometrics. Evaluation / calcium / Chemical reactions / cold / Covalent bonds / electric field / Electric fields / Exact sciences and technology / Flexibility / Information and communication sciences / Information science. Documentation / Ions / Library and information science. General aspects / Molecular beams / Molecular chemistry / Orientation / Rotational / Sciences and techniques of general use