Most evidence suggests that the proton in
bisulfite ion is located on sulfur, giving rise to C3v symmetry.
There is, however, some evidence from 17O NMR spectroscopy to
suggest that two tautomeric forms of HSO3- exist in dynamic
equilibrium, one having C3v symmetry (protonated at sulfur) and
other Cs symmetry (protonated at oxygen)[1]. The C3v
structure is supported by X-ray crystallography and, in aqueous solution, by
Raman spectroscopy v(S-H) = 2500 cm-1).




