Sulfamic acid
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{{Chembox new
| Name = Sulfamic acid
| ImageFile = Sulfamic.png
<!-- | ImageSize = 300px -->
| ImageName = Sulfamic acid
| IUPACName = Sulfamic acid
| Section1 = {{Chembox Identifiers
| CASNo = 5329-14-6
| SMILES = H<sub>2</sub>-N-SO<sub>3</sub>-H
}}
| Section2 = {{Chembox Properties
| Formula = H<sub>3</sub>NSO<sub>3</sub>
| MolarMass = 97.10 g/mol
| MeltingPt = 205 °C (401 °F)
| BoilingPt = Decomposes
| Density = 2.15 g/cm<sup>3</sup>
| 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 H<sub>3</sub>NSO<sub>3</sub>. This colorless, water-soluble compound finds many applications.
Sulfamic acid (H<sub>3</sub>NSO<sub>3</sub>) may be considered an intermediate compound between [[sulfuric acid]] (H<sub>2</sub>SO<sub>4</sub>), and [[sulfamide]] (H<sub>4</sub>N<sub>2</sub>SO<sub>2</sub>), effectively - though see [[#Structure and reactivity|below]] - replacing an -OH group with an -NH<sub>2</sub> group at each step. This pattern can extend no further in either direction without breaking down the -SO<sub>2</sub> group.
==Structure and reactivity==
First, it should be noticed that the compound is well described by the formula H<sub>3</sub>NSO<sub>3</sub>, not the [[tautomer]] H<sub>2</sub>NSO<sub>2</sub>(OH). The relevant bond distances are S=O, 1.44 and S-N 1.77 [[Ångström|Å]]. The greater length of the S-N distance is consistent with a single bond.<ref>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.</ref> Furthermore, a [[neutron diffraction]] study located the hydrogen atoms, all three of which are 1.03 [[Ångström|Å]] distant from nitrogen. The structures shown with this article are for the two main [[tautomer]]s.
Sulfamic acid is a weak acid, K<sub>a</sub> = 1.01 x 10<sup>−1</sup>. 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 [[ammonia|NH<sub>3</sub>]] solution to give [HNSO<sub>3</sub>]<sup>2−</sup>.
:<math>\mathrm{(NH_2)HSO_3 + NaOH \rightarrow NaNH_2SO_3 + H_2O}</math>
Sulfamic acid melts at 205 °C before decomposing at higher temperatures to H<sub>2</sub>O, SO<sub>3</sub>, SO<sub>2</sub>, and N<sub>2</sub>.
With [[nitrous acid|HNO<sub>2</sub>]], sulfamic acid reacts to give [[nitrogen|N<sub>2</sub>]], while with [[nitric acid|HNO<sub>3</sub>]], it affords [[nitrous oxide|N<sub>2</sub>O]].
:<math>\mathrm{HNO_2 + (NH_2)HSO_3 \rightarrow H_2SO_4 + N_2 + H_2O}</math>
:<math>\mathrm{HNO_3 + (NH_2)HSO_3 \rightarrow H_2SO_4 + N_2O + H_2O}</math>
The behavior of H<sub>3</sub>NSO<sub>3</sub> resembles that of [[urea]], (H<sub>2</sub>N)<sub>2</sub>CO, in some ways. Both feature [[amino group]]s linked to electron-withdrawing centers that can participate in [[delocalized bond]]ing. 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 [[sodium hydroxide|NaOH]] gives C<sub>6</sub>H<sub>11</sub>NHSO<sub>3</sub>Na, [[sodium cyclamate]]. Related compounds are also [[sweetener]]s, see [[acesulfame potassium]].
[[Sulfamate]]s (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 [[antibiotic]]s, nucleoside/nucleotide [[human immunodeficiency virus]] (HIV) [[reverse transcriptase inhibitor]]s, [[HIV protease inhibitor]]s (PIs), anti-cancer drugs ([[steroid sulfatase]] and [[carbonic anhydrase]] inhibitors), anti-[[epilepsy|epileptic]] drugs, and [[weight loss drug]]s.
Sulfamic acid is used as an acidic [[cleaning]] agent, typically for [[metal]]s and [[ceramic]]s. It is a replacement for [[hydrochloric acid]] for the removal of [[rust]]. In households, it is often found as a [[descaling agent]] in [[detergent]]s used for removal of [[limescale]].
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 resin]]s
*Ingredient in [[fire retardant|fire extinguishing media]]
*Pulp and paper industry as a chloride stabilizer
*Synthesis of [[nitrous oxide]] by reaction with nitric acid
==References==
{{Citationstyle|date=September 2007}}
{{reflist}}
*J. W. Bats, P. Coppens, T. F. Koetzle "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.
*[[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
* {{Greenwood&Earnshaw}}
==External links==
{{commonscat|Sulfamic acid}}
[[Category:Sulfur compounds]]
[[Category:Acids]]
[[Category:Household chemicals]]
[[Category:Cleaning product components]]
[[de:Amidosulfonsäure]]
[[it:Acido ammidosolfonico]]
[[ja:スルファミン酸]]
[[tr:Sulfamik asit]]
[[zh:氨基磺酸]]