Sulfamic acid

Chembox new
Name = Sulfamic acid
ImageFile = Sulfamic.png ImageName = Sulfamic acid
IUPACName = Sulfamic acid
Section1 = Chembox Identifiers
CASNo = 5329-14-6
SMILES = H₂-N-SO₃-H
Section2 = Chembox Properties
Formula = H₃NSO₃
MolarMass = 97.10 g/mol
MeltingPt = 205 °C (401 °F)
BoilingPt = Decomposes
Density = 2.15 g/cm³
pKa = 1.18 (1% solution @25 °C (77 °F)
Solvent = other solvents
SolubleOther = Soluble

Sulfamic acid, also known as amidosulfonic acid, amidosulfuric acid, aminosulfonic acid, and sulfamidic acid, is a molecular compound with the formula H₃NSO₃. This colorless, water-soluble compound finds many applications.

Sulfamic acid (H₃NSO₃) may be considered an intermediate compound between sulfuric acid (H₂SO₄), and sulfamide (H₄N₂SO₂), effectively - though see below - replacing an -OH group with an -NH₂ group at each step. This pattern can extend no further in either direction without breaking down the -SO₂ group.

tructure and reactivity

First, it should be noticed that the compound is well described by the formula H₃NSO₃, not the tautomer H₂NSO₂(OH). The relevant bond distances are S=O, 1.44 and S-N 1.77 Å. The greater length of the S-N distance is consistent with a single bond. [J. W. Bats, P. Coppens, T. F. Koetzle " [http://dx.doi.org/10.1107/S0567740877002568 The Experimental Charge Density in Sulfur-Containing Molecules: A Study of the Deformation Electron Density in Sulfamic Acid at 78 K by X-ray and Neutron Diffraction] " "Acta Crystallographica" 1977, "B33", pages 37–45.] Furthermore, a neutron diffraction study located the hydrogen atoms, all three of which are 1.03 Å distant from nitrogen cite journal | author = R. L. Sass | year = 1960 | title = A neutron diffraction study on the crystal structure of sulfamic acid | journal = Acta Cryst. | volume = 13 | issue = 4 | month = April | pages = 320-324 | doi = 10.1107/S0365110X60000789 ] . The structures shown with this article are for the two main tautomers.

Sulfamic acid is a weak acid, "K"_a = 1.01 x 10⁻¹. Because the solid is non-hygroscopic, it is used as a standard in acidometry (quantitative assays of acid content). Double deprotonation can be effected in NH₃ solution to give [HNSO₃] ²⁻.:$mathrm\{(NH\_2)HSO\_3\; +\; NaOH\; ightarrow\; NaNH\_2SO\_3\; +\; H\_2O\}$

Sulfamic acid melts at 205 °C before decomposing at higher temperatures to H₂O, SO₃, SO₂, and N₂.

Water solutions are unstable and slowly hydrolyze to ammonium bisulfate, but the crystalline solid is indefinitely stable under ordinary storage conditions.

With HNO₂, sulfamic acid reacts to give N₂, while with HNO₃, it affords N₂O.:$mathrm\{HNO\_2\; +\; (NH\_2)HSO\_3\; ightarrow\; H\_2SO\_4\; +\; N\_2\; +\; H\_2O\}$:$mathrm\{HNO\_3\; +\; (NH\_2)HSO\_3\; ightarrow\; H\_2SO\_4\; +\; N\_2O\; +\; H\_2O\}$

The behavior of H₃NSO₃ resembles that of urea, (H₂N)₂CO, in some ways. Both feature amino groups linked to electron-withdrawing centers that can participate in delocalized bonding. Both liberate ammonia upon heating in water.

Applications

The most famous application of sulfamic acid is in the synthesis of compounds that taste sweet. Reaction with cyclohexylamine followed by addition of NaOH gives C₆H₁₁NHSO₃Na, sodium cyclamate. Related compounds are also sweeteners, see acesulfame potassium.

Sulfamates (O-substituted-, N-substituted-, or di-/tri-substituted derivatives of sulfamic acid) have been used in the design of many types of therapeutic agents such as antibiotics, nucleoside/nucleotide human immunodeficiency virus (HIV) reverse transcriptase inhibitors, HIV protease inhibitors (PIs), anti-cancer drugs (steroid sulfatase and carbonic anhydrase inhibitors), anti-epileptic drugs, and weight loss drugs.

Sulfamic acid is used as an acidic cleaning agent, typically for metals and ceramics. It is a replacement for hydrochloric acid for the removal of rust. In households, it is often found as a descaling agent in detergents used for removal of limescale. From all acid, Sulfamic acid has the best water descaling property, thus also its application in cleaning dairy farm equipment and beer brewery. Although it is considered less corrosive than hydrochloric acid, in its application as acid cleaning, it is very common to find user adding corrosion inhibitor.

Sulfamic acid is used in the S.C. Johnson & Sons, Inc. "Scrubbing Bubbles Fizz-Its Toilet Tablets."

*Catalyst for esterification process
*Dye and pigment manufacturing
*Herbicide
*Ingredient in Denture Tablets
*Coagulator for urea-formaldehyde resins
*Ingredient in fire extinguishing media. Sulfamic acid is the main raw material for Ammonium_sulfamate which is a widely used herbicide and fire retardant material for household product.
*Pulp and paper industry as a chloride stabilizer
*Synthesis of nitrous oxide by reaction with nitric acid

References

*MSDS http://www.osha.gov [http://www.osha.gov/dts/chemicalsampling/data/CH_268428.html]
*Sulfamates and their therapeutic potential. Med Res Rev. 2005 Mar;25(2):186-228. Review.
*R. J. Cremlyn “An Introduction to Organosulfur Chemistry” John Wiley and Sons: Chichester (1996). ISBN 0-471-95512-4
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External links