Rotational Spectroscopy Studies on Hydrogen Bonding

Proton transfer across a hydrogen bond represents the simplest of chemical reactions, but one which

often requires the presence of near-neighbors to stabilize the resulting charge separation. We present

the results of microwave spectroscopic investigations of a variety of gas phase acid-base pairs and

consider the degree to which proton transfer takes place. Spectra are presented for the

CF₃COOH···N(CH₃)₃ adduct, and several metrics are used to assess the degree to which the terms

“hydrogen bonded” and “proton-transferred ion pair” provide adequate descriptions. The use of

superacids to promote observable proton transfer is also discussed, and spectra are presented for the

mono- and dihydrates of fluorosulfonic acid, viz., FSO₂OH···(H₂O)_n=1,2. The experimental work is

interpreted in the context of accompanying computational results.