| Sulfamic acid | |
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Sulfamic acid |
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| Identifiers | |
| CAS number | 5329-14-6 |
| PubChem | 5987 |
| ChemSpider | 5767 |
| EC number | 226-218-8 |
| UN number | 2967 |
| ChEBI | CHEBI:9330 |
| ChEMBL | CHEMBL68253 |
| RTECS number | WO5950000 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | H3NSO3 |
| Molar mass | 97.10 g/mol |
| Density | 2.15 g/cm3 |
| Melting point |
205 °C decomp. |
| Solubility in water | moderate, with slow hydrolysis |
| Acidity (pKa) | 1.0[1] |
| Hazards | |
| MSDS | ICSC 0328 |
| EU Index | 016-026-00-0 |
| EU classification | Irritant (Xi) |
| R-phrases | R36/38 R52/53 |
| S-phrases | (S2) S26 S28 S61 |
| Related compounds | |
| Other cations | Ammonium sulfamate |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
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.
Sulfamates are O-substituted-, N-substituted-, or di-/tri-substituted derivatives of sulfamic acid.
Contents |
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.[2] Furthermore, a neutron diffraction study located the hydrogen atoms, all three of which are 1.03 Å distant from nitrogen.[3] In the solid state, the molecule of sulfamic acid is well described by a zwitterionic form :
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acid zwitterion in the crystal[3] |
Sulfamic acid is a moderately strong acid, Ka = 1.01 x 10−1. Because the solid is non-hygroscopic, it is used as a standard in acidimetry (quantitative assays of acid content).
Double deprotonation can be effected in NH3 solution to give [HNSO3]2−.
Sulfamic acid melts at 205 °C before decomposing at higher temperatures to H2O, SO3, SO2, and N2.[4]
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.
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.
The most famous application of sulfamic acid is in the synthesis of sweet-tasting compounds. Reaction with cyclohexylamine followed by addition of NaOH gives C6H11NHSO3Na, sodium cyclamate. Related compounds are also sweeteners, see acesulfame potassium.
Sulfamates 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.[5]
Sulfamic acid is used as an acidic cleaning agent, sometimes pure or as a component of proprietary mixtures, typically for metals and ceramics. It is frequently used for removing rust and limescale, replacing the more volatile and irritating hydrochloric acid, which is however cheaper. It is often a component of household descaling agents, for example, Lime-A-Way Thick Gel contains up to 8% sulfamic acid and pH 2 - 2.2,[6] or detergents used for removal of limescale. When compared to most of the common strong mineral acids, Sulfamic acid has desirable water descaling properties, low volatility, low toxicity and is a water soluble solid forming soluble calcium and iron-III salts. Its also finds applications in the industrial cleaning of dairy and brew-house equipment. Although it is considered less corrosive than hydrochloric acid, corrosion inhibitors are often added to commercial cleansers of which it is a component. It is possible that the amino group could act as a ligand under certain circumstances, as does the chloride ion for Fe-III, when hydrochloric acid is used in rust removal.
Sulfamic acid is used in the S.C. Johnson & Sons, Inc. "Scrubbing Bubbles Fizz-Its Toilet Tablets", and in the Saeco Dezcal descaling powder for home coffee and espresso equipment.
According to the label on the consumer product, the liquid silver cleaning product TarnX contains thiourea, a detergent, and sulfamic acid.
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