Rongalite

See also: Hyposulfite which is used as a synonym of sulfoxylate.
Rongalite
IUPAC name

Sodium hydroxymethanesulfinate
Other names

Rongalite
Sodium formaldehydesulfoxylate
Identifiers
CAS number 149-44-0 Y, 
[6035-47-8], dihydrate
PubChem 8999
ChemSpider 8649 Y
UNII X4ZGP7K714 Y
RTECS number PB0380000
Jmol-3D images Image 1
Properties
Molecular formula CH3NaO3S
Molar mass 118.10 g/mol
154.14 g/mol, dihydrate
Appearance colorless crystals
Density 1.75 g/cm3, dihydrate
Melting point

64.5 °C, dihydrate
Solubility in water 600 g/L, dihydrate (approximate)
Acidity (pKa) decomp. at low pH
Structure
Molecular shape pyramidal at S
Hazards
R/S statement R: 36/37/38 S:26-36
Main hazards non-toxic
Related compounds
Related compounds SO32-, CH2O
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Rongalite, also called Rongalit (registered trademark of BASF) is sodium hydroxymethylsulfinate, or Na+HOCH2SO2-. The salt has many names, including also sodium formaldehyde sulfoxylate and Bruggolite. It is water-soluble and generally sold as the dihydrate.

Contents

Reactions

This salt is prepared from sodium dithionite:

Na2S2O4 + 2 CH2O + H2O → NaHOCH2SO3 + NaHOCH2SO2

This reaction proceeds quantitatively, such that dithionite can be determined by its conversion to rongalite, which is far less O2-sensitive and thus easier to handle.

The hydroxymethanesulfinate ion is unstable in solution towards decomposition to formaldehyde and sulfoxylate ion, however addition of at least one equivalent of formaldehyde pushes the equilibrium towards the side of the adduct and reacts further to give the bis-(hydroxymethyl)sulfone. Such solutions are shelf-stable indefinitely.

NaHOCH2SO2 can essentially be considered to be a source of SO22-. As such it is used both as a reducing agent and as a reagent to introduce SO2 groups into organic molecules. Treatment of elemental Se and Te with NaHOCH2SO2 gives solutions containing the corresponding Na2Sex and Na2Tex, where x is approximately 2. As a nucleophile, NaHOCH2SO2 reacts with alkylating agents to give sulfones.

NaHOCH2SO2 + 2 C6H5CH2Br → [C6H5CH2]2SO2 + NaBr + CH2O + HBr

Occasionally, alkylation will occur also at oxygen, thus α,α'-dibromoxylene gives both the sulfone and the isomeric sulfinate ester.

Use

The original use of the compound was as industrial bleaching agent and as a reducing agent for vat dying. The other dominating use today is the application as reducing agent in redox-initiator systems for emulsion polymerization. One of the typical redox pair examples is t-butyl peroxide. A niche use is its use as water conditioner for aquaria as it rapidly reduces chlorine and chloramine and reacts with ammonia to form the innocuous aminomethylsulfinate ion. [1] It is also used as an antioxidant in pharmaceutical formulation.

Zinc formaldehyde sulfoxylate

The zinc complex Zn(HOCH2SO2]2 is marketed under the trademarks Decroline, Decolin, and Safolin. This compound is an additive in polymers and textiles.[2]

References

  1. ^ EPEP0278515, Inventor Günter Ritter, issued 11 Feb 1988 to Tetra-Werke, 49324 Melle, Germany.
  2. ^ Masciocchi, N.; Rigamonti, C. and Maspero, A., "Poly[di-μ3-hydroxymethanesulfinato-zinc(II)]", Acta Crystallographica Section E: Structure Reports Online, 2005, volume E61, m2683-m2685.