Tetra-n-alkylammonium bisulphites: a new example of the existence of the bisulphite ion in solid compounds

Liquid sulphur dioxide reacts with aqueous NR4OH (R = Et, Bun, or n-pentyl) solutions to form the corresponding bisulphite. I.r. studies indicate that the compounds contain the bisulphite ion with structure H–SO3–, having essentially C3v symmetry. The preparative method used is that which leads to the formation of tetramethylammonium pyrosulphite when tetramethylammonium hydroxide is treated with sulphur dioxide. Tetra-n-propylammonium hydroxide, on treatment with sulphur dioxide, yields tetra-n-propylammonium pyrosulphite. The i.r. spectra of the tetra-alkylammonium bisulphites and pyrosulphites are recorded and discussed.