Chlorosulfuric acid
From Wikipedia, the free encyclopedia
| Chlorosulfuric acid | |
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| IUPAC name | chlorosulfonic acid |
| Other names | chloridosulfonic acid,
sulfuric chlorohydrin |
| Identifiers | |
| CAS number | [7790-94-5] |
| RTECS number | FX5730000 |
| SMILES | O=S(O)(Cl)=O |
| Properties | |
| Molecular formula | HSO3Cl |
| Molar mass | 116.52 g mol−1 |
| Appearance | colorless liquid that fumes in air |
| Density | 1.753 g cm−3 |
| Melting point |
−80 °C |
| Boiling point |
151-152 °C (755 mm Hg) |
| Solubility in other solvents | reacts with water, alcohols soluble in chlorocarbons |
| Refractive index (nD) | 1.433 |
| Structure | |
| Molecular shape | tetrahedral |
| Hazards | |
| Main hazards | corrosive evolves HCl upon hydrolysis |
| NFPA 704 |
 4
2
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| R-phrases | 14-35-37 |
| S-phrases | 26-45 |
| Related compounds | |
| Related compounds | sulfuryl chloride sulfuric acid |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references |
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Chlorosulfuric acid is ClSO2OH. This tetrahedral molecule is an intermediate, chemically and conceptually, between SO2Cl2 and H2SO4. It is also known as chlorosulfonic acid. It is a distilable, colorless liquid that should be handled with care. It is a hygroscopic and a powerful lachrymator.
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[edit] Synthesis
The industrial synthesis entails the reaction of hydrogen chloride with a solution of sulfur trioxide in sulfuric acid:
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- HCl + SO3 → ClSO2OH
It can also be prepared by chlorination of sulfuric acid, written here for pedagogical purposes as SO2(OH)2, vs. the usual format H2SO4:
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- PCl5 + SO2(OH)2 → ClSO2OH + POCl3 + HCl
The latter method is more suited for laboratory-scale operations.
[edit] Related compounds
- FSO2OH is a strong acid and shows only a mild tendency to evolve HF.
- Bromosulfonic acid, BrSO2OH, is unstable, decomposing at its melting point of 8°C to give Br2, SO2, and H2SO4.
- Iodosulfonic acid is unknown.
[edit] Applications
ClSO2OH is used to prepare sulfonic acids, which are useful in detergents and as chemical intermediates.
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- R-H + ClSO2OH → RSO2OH + HCl
An early synthesis of saccharin begins with the reaction of toluene with ClSO2OH to give the ortho- and para-toluene sulfonyl chloride derivatives:
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- CH3C6H5 + ClSO2OH → CH3C6H4SO2Cl + HCl
Oxidation of the ortho isomer gives the benzoic acid derivative that then is cyclized with ammonia and neutralized with base to afford saccharin.
[edit] Safety considerations
ClSO2OH reacts violently with water to release HCl. Inhalation of ClSO2OH would generate HCl in the lungs, which is very dangerous. Thus, precautions associated with HCl should be observed.
[edit] References
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The references in this article would be clearer with a different or consistent style of citation, footnoting, or external linking. |
- Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001, pages 549-550 (discussion of XSO2OH for X = F, Cl, Br, I)
- R.J. Cremlyn, "Chlorosulfonic Acid" Springer-Verlag New York, Inc. (Royal Society of Chemistry, 2002, 300 pp. ISBN 978-0-85404-498-6
