The structure of the dithionite ion

Abstract The Raman spectra of aqueous and solid sodium dithionite have been recorded. Differences in the location, intensity, and number of observed bands are attributed to conformational changes in the dithionite ion. The structure of the aqueous ion is non-planar with a C 2h symmetry with an SS bond distance estimated to be 0.220–0.226 nm, as opposed to the dithionite structure in the Na 2 S 2 O 4 ·2H 2 O salt which is known to have C 2 ν structure with a bond distance of 0.2389 nm. The Raman spectra of aqueous dithionite are assigned to A g (SO) = 997 cm −1 ; B g (SO) at 912 cm −1 , B g SO 2 twist at 324 cm −1 . The remaining bands are a strong A g , the SO 2 wag, the SO 2 scissor, and the SS stretch at 584, 461, and 232 cm −1 , respectively, but due to coupling all three motions are expected to exhibit substantial SS character. The variation of the spectra of the solid and aqueous sodium dithionite indicate strong environmental effect on the structure of the anion.