Barrier to Proton Transfer in the Dimer of Formic Acid: A Pure Rotational Study

Measure for measure: The rotational spectrum of the dimer of the prototype of carboxylic acids, formic acid has been measured—the first time for a non‐polar dimer—thanks to the tiny dipole moment induced by an asymmetric isotopic substitution. From the experimental tunneling splitting, the height of the barrier to proton transfer has been determined.

Abstract

The rotational spectra of three C‐deuterated isotopologues of the dimer of formic acid have been measured, thanks to the small dipole moment induced by asymmetric H→D substitution(s). For the DCOOH–HCOOH species, the concerted double proton transfer of the two hydroxy hydrogen atoms takes place between two equivalent minima and generates a tunneling splitting of 331.2(6) MHz. This splitting can be reproduced by a 3D model with a barrier of 2559 cm⁻¹ (30.6 kJ mol⁻¹) as obtained from theoretical calculations.

from A via a.sfakia on Inoreader https://ift.tt/2r5r30V