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Chlorosulfuric acid

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Chlorosulfuric acid
Structural formula of chlorosulfuric acid
Ball-and-stick model of the chlorosulfuric acid molecule
Names
IUPAC name Sulfurochloridic acid
Other names Chlorosulfuric acid,
Chlorosulfonic acid,
Chlorosulphonic acid,
Chlorinesulfonic acid,
Chlorinesulphonic acid,
Chloridosulfonic acid,
Chloridosulphonic acid,
Sulfuric chlorohydrin
Identifiers
CAS Number
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.029.304 Edit this at Wikidata
EC Number
  • 232-234-6
PubChem CID
RTECS number
  • FX5730000
UNII
UN number 1754
CompTox Dashboard (EPA)
InChI
  • InChI=1S/ClHO3S/c1-5(2,3)4/h(H,2,3,4)Key: XTHPWXDJESJLNJ-UHFFFAOYSA-N
  • InChI=1/ClHO3S/c1-5(2,3)4/h(H,2,3,4)Key: XTHPWXDJESJLNJ-UHFFFAOYAO
SMILES
  • ClS(=O)(=O)O
Properties
Chemical formula HSO3Cl
Molar mass 116.52 g mol
Appearance colorless liquid, but commercial samples usually are pale brown
Density 1.753 g cm
Melting point −80 °C (−112 °F; 193 K)
Boiling point 151 to 152 °C (304 to 306 °F; 424 to 425 K) (755 mmHg or 100.7 kPa)
Solubility in water hydrolysis
Solubility in other solvents reacts with alcohols
soluble in chlorocarbons
Acidity (pKa) −5.9 (in CF3CO2H)
Refractive index (nD) 1.433
Structure
Molecular shape tetrahedral
Hazards
GHS labelling:
Pictograms GHS05: CorrosiveGHS07: Exclamation mark
Signal word Danger
Hazard statements H314, H335
Precautionary statements P260, P261, P264, P271, P280, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P312, P321, P363, P403+P233, P405, P501
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 0: Will not burn. E.g. waterInstability 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g. white phosphorusSpecial hazard W+OX: Reacts with water in an unusual or dangerous manner AND is oxidizer
3 0 2W
OX
Safety data sheet (SDS) ICSC 1039
Related compounds
Related compounds Sulfuryl chloride
Sulfuric acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). checkY verify (what is  ?) Infobox references
Chemical compound

Chlorosulfuric acid (IUPAC name: sulfurochloridic acid) is the inorganic compound with the formula HSO3Cl. It is also known as chlorosulfonic acid, being the sulfonic acid of chlorine. It is a distillable, colorless liquid which is hygroscopic and a powerful lachrymator. Commercial samples usually are pale brown or straw colored.

Salts and esters of chlorosulfuric acid are known as chlorosulfates.

Structure and properties

Chlorosulfuric acid is a tetrahedral molecule. Its structure was debated for many decades until in 1941 Shrinivasa Dharmatti proved by magnetic susceptibility that chlorine is directly bonded to sulfur.

The formula is more descriptively written SO2(OH)Cl, but HSO3Cl is traditional. It is an intermediate, chemically and conceptually, between sulfuryl chloride (SO2Cl2) and sulfuric acid (H2SO4). The compound is rarely obtained pure. Upon standing with excess sulfur trioxide, it decomposes to pyrosulfuryl chlorides:

2 ClSO3H + SO3 → H2SO4 + S2O5Cl2

Synthesis

The industrial synthesis entails the reaction of hydrogen chloride with a solution of sulfur trioxide in sulfuric acid:

HCl + SO3 → ClSO3H

It can also be prepared by the method originally used by acid's discoverer Alexander William Williamson in 1854, namely chlorination of sulfuric acid, written here for pedagogical purposes as HSO3(OH) vs. the usual format H2SO4:

PCl5 + HSO3(OH) → HSO3Cl + POCl3 + HCl

The latter method is more suited for laboratory-scale operations.

Williamson's discovery disproved then-popular hypothesis that sulfuric acid is a compound of water (which was incorrectly assumed to have formula of HO) and sulfur trioxide.

Applications

ClSO2OH is used to prepare alkyl sulfates, which are useful as detergents and as chemical intermediates:

ROH + ClSO3H → ROSO3H + HCl

One historical synthesis of saccharin begins with the reaction of toluene with ClSO2OH to give the ortho- and para-toluenesulfonyl chloride derivatives:

CH3C6H5 + 2 ClSO2OH → CH3C6H4SO2Cl + H2SO4 + HCl

Oxidation of the ortho isomer gives the benzoic acid derivative that then is cyclized with ammonia and neutralized with base to afford saccharin.

Chlorosulfonic acid has been used as an anti-contrail agent in Ryan Model 147 reconnaissance drones, and to produce smoke screens.

Safety

ClSO3H reacts violently with water to yield sulfuric acid and hydrogen chloride, which are corrosive:

ClSO3H + H2O → H2SO4 + HCl

Related halosulfuric acids

References

  1. Perrin, D. D., ed. (1982) . Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution. IUPAC Chemical Data (2nd ed.). Oxford: Pergamon (published 1984). Entry 32. ISBN 0-08-029214-3. LCCN 82-16524.
  2. "New Environment Inc. - NFPA Chemicals".
  3. Cremlyn, R. J. (2002). Chlorosulfonic Acid. Royal Society of Chemistry. ISBN 978-0-85404-498-6.
  4. ^ Kirk, Raymond Eller; Othmer, Donald Frederick (1964). Encyclopedia of Chemical Technology. Interscience Publishers.
  5. Dharmatti, S. S. (1941-05-01). "Magnetism and Molecular Structure of Sulphur Compounds". Proceedings of the Indian Academy of Sciences - Section A. 13 (5): 359–370. doi:10.1007/BF03049293. ISSN 0370-0089.
  6. Holleman, A. F.; Wiberg, E. (2001). Inorganic Chemistry. San Diego: Academic Press. pp. 549–550.
  7. ^ Bergen, Elvira; Maas, J.; Baunack, F. (2024). "Chlorosulfuric Acid". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a07_017.pub2. ISBN 3527306730.
  8. "The Quiet Revolution".
  9. Method and apparatus for suppressing contrails (PDF). United States Patent and Trademark Office. 1970.
  10. The Royal Navy at War (DVD). London: Imperial War Museum. 2005.
  11. Amos, Jonathan (2018-04-11). "Nazi legacy found in Norwegian trees". BBC News Online. Retrieved 2018-04-17.
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