Sulfamic acid

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Sulfamic acid
Tautomerism of sulfamic acid
Ball-and-stick model of the canonical neutral form
Ball-and-stick model of the canonical neutral form
Ball-and-stick model of the zwitterionic form
Ball-and-stick model of the zwitterionic form
Names
IUPAC name
Sulfamic acid
Identifiers
3D model (
JSmol
)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard
 100.023.835 Edit this at Wikidata
EC Number
  • 226-218-8
25628
RTECS number
  • WO5950000
UNII
UN number 2967
  • InChI=1S/H3NO3S/c1-5(2,3)4/h(H3,1,2,3,4) checkY
    Key: IIACRCGMVDHOTQ-UHFFFAOYSA-N checkY
  • InChI=1/H3NO3S/c1-5(2,3)4/h(H3,1,2,3,4)
    Key: IIACRCGMVDHOTQ-UHFFFAOYAK
Properties
H3NSO3
Molar mass 97.10 g/mol
Appearance white crystals
Density 2.15 g/cm3
Melting point 205 °C (401 °F; 478 K) decomposes
Moderate, with slow hydrolysis
Solubility
  • Moderately soluble in DMF
  • Slightly soluble in MeOH
  • Insoluble in hydrocarbons
Acidity (pKa) 1.0[1]
Hazards
GHS labelling:
GHS07: Exclamation mark
Warning
H315, H319, H412
P264, P273, P280, P302+P352, P305+P351+P338, P321, P332+P313, P337+P313, P362, P501
Safety data sheet (SDS) ICSC 0328
Related compounds
Other cations
 Ammonium sulfamate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

Sulfamic acid, also known as amidosulfonic acid, amidosulfuric acid, aminosulfonic acid, sulphamic acid and sulfamidic acid, is a molecular compound with the formula H3NSO3. This colourless, water-soluble compound finds many applications. Sulfamic acid melts at 205 °C before decomposing at higher temperatures to water, sulfur trioxide, sulfur dioxide and nitrogen.[2]

Sulfamic acid (H3NSO3) may be considered an intermediate compound between

sulfonyl
(–SO2–) moiety. Sulfamates are derivatives of sulfamic acid.

Production

Sulfamic acid is produced industrially by treating urea with a mixture of sulfur trioxide and sulfuric acid (or oleum). The conversion is conducted in two stages, the first being sulfamation:

OC(NH2)2 + SO3 → OC(NH2)(NHSO3H)
OC(NH2)(NHSO3H) + H2SO4 → CO2 + 2 H3NSO3

In this way, approximately 96,000 tonnes were produced in 1995.[3]

Structure and reactivity

Ball-and-stick model of a sulfamic acid zwitterion as it occurs in the crystal state.[4]

The compound is well described by the formula H3NSO3, not the

zwitterionic
form.

Hydrolysis

The crystalline solid is indefinitely stable under ordinary storage conditions, however, aqueous solutions of sulfamic acid slowly hydrolyse to ammonium bisulfate, according to the following reaction:

H3NSO3 + H2O → [NH4]+[HSO4]−

Its behaviour resembles that of

amino groups linked to electron-withdrawing centres that can participate in delocalised bonding. Both liberate ammonia upon heating in water, with urea releasing CO2 while sulfamic acid releases sulfuric acid
.

Acid–base reactions

Sulfamic acid is a moderately strong acid, Ka = 0.101 (pKa = 0.995). Because the solid is not

acidimetry
(quantitative assays of acid content).

H3NSO3 + NaOH → NaH2NSO3 + H2O

Double deprotonation can be effected in liquid ammonia to give the anion HNSO2−
3.[6]

H3NSO3 + 2 NH3 → HNSO2−
3 + 2 NH+
4

Reaction with nitric and nitrous acids

With nitrous acid, sulfamic acid reacts to give nitrogen:

HNO2 + H3NSO3 → H2SO4 + N2 + H2O

while with concentrated nitric acid, it affords nitrous oxide:[7]

HNO3 + H3NSO3 → H2SO4 + N2O + H2O

Reaction with hypochlorite

The reaction of excess hypochlorite ions with sulfamic acid or a sulfamate salt gives rise reversibly to both N-chlorosulfamate and N,N-dichlorosulfamate ions.[8][9][10]

HClO + H2NSO3H → ClNHSO3H + H2O
HClO + ClNHSO3H ⇌ Cl2NSO3H + H2O

Consequently, sulfamic acid is used as hypochlorite

aldehydes with chlorite such as the Pinnick oxidation
.

Reaction with alcohols

Upon heating sulfamic acid will react with alcohols to form the corresponding

chlorosulfonic acid or oleum, but is also significantly milder and will not sulfonate aromatic rings. Products are produced as their ammonium salts. Such reactions can be catalyzed by the presence of urea.[10]
Without the presence of any catalysts, sulfamic acid will not react with ethanol at temperatures below 100 °C.

ROH + H2NSO3H → ROS(O)2O− + NH+
4

An example of this reaction is the production 2-ethylhexyl sulfate, a wetting agent used in the

mercerisation of cotton, by combining sulfamic acid with 2-ethylhexanol
.

Applications

Sulfamic acid is mainly a precursor to sweet-tasting compounds. Reaction with

sodium cyclamate. Related compounds are also sweeteners, such as acesulfame potassium
.

Sulfamates have been used in the design of many types of therapeutic agents such as

weight loss drugs.[11]

Cleaning agent

Sulfamic acid is used as an acidic

mineral acids
, sulfamic acid has desirable water descaling properties, low volatility, and low toxicity. It forms water-soluble salts of calcium, nickel, and ferric iron.

Sulfamic acid is preferable to hydrochloric acid in household use, due to its intrinsic safety. If inadvertently mixed with hypochlorite based products such as bleach, it does not form chlorine gas, whereas the most common acids would; the reaction (neutralisation) with ammonia, produces a salt, as depicted in the section above.

It also finds applications in the industrial cleaning of dairy and brewhouse equipment. Although it is considered less corrosive than hydrochloric acid, corrosion inhibitors are often added to the commercial cleansers of which it is a component. It can be used as a descalant for descaling home coffee and espresso machines and in denture cleaners.

Other uses

  • esterification
    process
  • Dye and pigment manufacturing
  • Herbicide
  • Descalant for scale removal
  • 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 products.
  • Pulp and paper industry as a chloride stabilizer
  • Synthesis of nitrous oxide by reaction with nitric acid
  • The deprotonated form (sulfamate) is a common counterion for nickel(II) in electroplating.
  • Used to separate nitrite ions from mixture of nitrite and nitrate ions( NO3−+ NO2−) during qualitative analysis of nitrate by
    Brown Ring test
    .
  • Obtaining deep eutectic solvents with urea[13]

Silver polishing

According to the label on the consumer product, the silver cleaning product TarnX contains thiourea, a detergent, and sulfamic acid.

References

  1. doi:10.1039/JR9600004236
    .
  2. ISBN 0471238961
    .
  3. ISBN 978-3527306732
    .
  4. ^
    doi:10.1107/S0365110X60000789
    .
  5. doi:10.1107/S0567740877002568
    .
  6. doi:10.1021/ed020p189
    .
  7. doi:10.1021/ic50190a080
    .
  8. ^ US 3328294, Self, Richard W.; Watkins Jr., Joseph C. & Sullins, John K., "Process for control of micro-organisms in process streams", published 1967-06-27, assigned to Mead Corp. 
  9. ^ FR 2087248, "Systèmes aqueux stables contenant un composé N-hydrogéné et un hypohalogénite [Stable aqueous systems containing an N-hydrogenated compound and a hypohalogenite]", published 1971-12-31, assigned to E. I. Du Pont De Nemours & Co. 
  10. ^
    ISSN 0009-2665
    .
  11. S2CID 1361433
    .
  12. ^ Benckiser, Reckitt. "Material Safety Data Sheet – Lime-A-Way Lime, Calcium and Rust Cleaner (Trigger Spray)" (PDF). hardwarestore.com. Archived from the original (PDF) on 17 July 2011. Retrieved 17 November 2011.
  13. ^ Kazachenko, Aleksandr S.; Issaoui, Noureddine; Medimagh, Mouna; Yu. Fetisova, Olga; Berezhnaya, Yaroslava D.; Elsuf'ev, Evgeniy V.; Al-Dossary, Omar M.; Wojcik, Marek J.; Xiang, Zhouyang; Bousiakou, Leda G. "Experimental and theoretical study of the sulfamic acid-urea deep eutectic solvent" (2022) Journal of Molecular Liquids, 363, art. no. 119859 DOI: 10.1016/j.molliq.2022.119859

Further reading

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