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Published on: February 15, 2016
Proton Transfer in a Bare Superacid-Amine Complex: A Microwave and Computational Study of Trimethylammonium Triflate
Nathan Love1, Anna K Huff1, Kenneth R Leopold1
1Department of Chemistry, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota 55455, United States.
Abstract:
The complex formed from trimethylamine ((CH3)3N) and trifluoromethanesulfonic acid (triflic acid, CF3SO3H) has been observed by Fourier transform microwave spectroscopy in a supersonic jet. Spectroscopic data, most notably 14N nuclear quadrupole coupling constants, are combined with computational results at several levels of theory to unambiguously demonstrate complete or near-complete proton transfer from the triflic acid to the trimethylamine upon complexation. Thus, the system is best regarded as a trimethylammonium triflate ion pair in the gas phase. The formation of an isolated ion pair in a 1:1 complex of a Brønsted acid and base is unusual and likely arises due to the strong acidity of triflic acid. Simple energetic arguments based on proton affinities and the Coulomb interaction energy can be used to rationalize this result.
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