STRUCTURE OF THE VAN DER WAALS PRECURSORS TO FLUORO- AND CHLOROSULFONIC ACIDS: MICROWAVE SPECTRA OF $HF-SO_{3}$ AND $HCl-SO_{3}$
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Date
1995
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Ohio State University
Abstract
The structures of $HF-SO_{3}$ and $HCl-SO_{3}$ have been determined by Fourier transform microwave spectroscopy. Both HF and HCL react with $SO_{3}$ to form halosulfonic acids, $HSO_{3}X (X=F.Cl)$, but the isomers observed correspond to more weakly bound minima on the potential energy surface. The halogen atom lies above the $SO_{3}$ plane in both systems, with S-F and S-Cl distances of $2.68 {\AA}$ and $3.11 {\AA}$, respectively. The equilibrium position of the proton is most likely off-axis, but large amplitude vibrational averaging produces an effective symmetric top structure in both cases. The observed geometries are indicative of weak donor-acceptor type interactions, with out-of-plane distortions of the $SO_{3}$ subunit of less than $1^{\circ}$. The complexes are compared with those of $BF_{3}$, whose Lewis acidity is generally regarded as less than that of $SO_{3}$.
Description
Author Institution: University of Minnesota, Minneapolis, MN 55455