:Chlorosulfuric acid

{{chembox

| Watchedfields = changed

| verifiedrevid = 477315288

| Name = Chlorosulfuric acid

| ImageFileL1 = Chlorosulfuric-acid.png

| ImageClassL1 = skin-invert-image

| ImageSizeL1 = 110px

| ImageAltL1 = Structural formula of chlorosulfuric acid

| ImageFileR1 = Chlorosulfuric acid molecule ball.png

| ImageClassR1 = bg-transparent

| ImageSizeR1 = 140px

| ImageAltR1 = Ball-and-stick model of the chlorosulfuric acid molecule

| ImageFile2 = Chlorosulfuric acid.png

| IUPACName = Sulfurochloridic acid

| OtherNames = Chlorosulfuric acid,
Chlorosulfonic acid,
Chlorosulphonic acid,
Chlorinesulfonic acid,
Chlorinesulphonic acid,
Chloridosulfonic acid,
Chloridosulphonic acid,
Sulfuric chlorohydrin

|Section1={{Chembox Identifiers

| SMILES = ClS(=O)(=O)O

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| ChemSpiderID = 23040

| PubChem = 24638

| InChI = 1/ClHO3S/c1-5(2,3)4/h(H,2,3,4)

| InChIKey = XTHPWXDJESJLNJ-UHFFFAOYAO

| StdInChI_Ref = {{stdinchicite|correct|chemspider}}

| StdInChI = 1S/ClHO3S/c1-5(2,3)4/h(H,2,3,4)

| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}

| StdInChIKey = XTHPWXDJESJLNJ-UHFFFAOYSA-N

| CASNo = 7790-94-5

| CASNo_Ref = {{cascite|correct|CAS}}

| UNII_Ref = {{fdacite|correct|FDA}}

| UNII = 2O9AXL1TJ4

| RTECS = FX5730000

| EC_number = 232-234-6

| UNNumber = 1754

}}

|Section2={{Chembox Properties

| Formula = HSO₃Cl

| MolarMass = 116.52 g mol⁻¹

| Appearance = colorless liquid, but commercial samples usually are pale brown

| Density = 1.753 g cm⁻³

| Solubility = hydrolysis

| Solvent = other solvents

| SolubleOther = reacts with alcohols
soluble in chlorocarbons

| MeltingPtC = −80

| BoilingPtC = 151 to 152

| BoilingPt_notes = ({{convert|755|mmHg|abbr=on|disp=or}})

| pKa = −5.9 (in CF₃CO₂H){{cite book|title=Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution|editor-first=D. D.|editor-last=Perrin|edition=2nd|series=IUPAC Chemical Data|issue=29|publisher=Pergamon|location=Oxford|year=1982|publication-date=1984|orig-date=1969|lccn=82-16524|isbn=0-08-029214-3|at=Entry 32}}

| RefractIndex = 1.433

}}

|Section3={{Chembox Structure

| MolShape = tetrahedral

| Dipole =

}}

|Section7={{Chembox Hazards

| ExternalSDS = [http://www.inchem.org/documents/icsc/icsc/eics1039.htm ICSC 1039]

| NFPA-H = 3

| NFPA-F = 0

| NFPA-R = 2

| NFPA-S = WOX

| GHSPictograms = {{GHS05}}{{GHS07}}

| GHSSignalWord = Danger

| HPhrases = {{H-phrases|314|335}}

| PPhrases = {{P-phrases|260|261|264|271|280|301+330+331|303+361+353|304+340|305+351+338|310|312|321|363|403+233|405|501}}

}}{{Cite web|url=http://www.newenv.com/resources/nfpa_chemicals|title = New Environment Inc. - NFPA Chemicals}}

|Section8={{Chembox Related

| OtherCompounds = Sulfuryl chloride
Sulfuric acid

}}

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.{{cite book | last = Cremlyn | first = R. J. | title = Chlorosulfonic Acid | publisher = Royal Society of Chemistry | year = 2002 | isbn = 978-0-85404-498-6}}

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.{{Cite book |last1=Kirk |first1=Raymond Eller |url=https://books.google.com/books?id=f8tTAAAAMAAJ&q=Dharmatti |title=Encyclopedia of Chemical Technology |last2=Othmer |first2=Donald Frederick |date=1964 |publisher=Interscience Publishers |language=en}}{{Cite journal |last=Dharmatti |first=S. S. |date=1941-05-01 |title=Magnetism and Molecular Structure of Sulphur Compounds |url=https://www.ias.ac.in/describe/article/seca/013/05/0359-0370 |journal=Proceedings of the Indian Academy of Sciences - Section A |language=en |volume=13 |issue=5 |pages=359–370 |doi=10.1007/BF03049293 |issn=0370-0089|url-access=subscription }}

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).{{cite book |last1=Holleman |first1=A. F. |last2=Wiberg |first2=E. | title = Inorganic Chemistry | publisher = Academic Press | location = San Diego | year = 2001 | pages = 549–550 }} The compound is rarely obtained pure. Upon standing with excess sulfur trioxide, it decomposes to pyrosulfuryl chlorides:{{cite encyclopedia |last1=Bergen|first1= Elvira|last2=Maas |first2=J. |last3=Baunack |first3=F. |title = Chlorosulfuric Acid | encyclopedia = Ullmann's Encyclopedia of Industrial Chemistry | year = 2024 |pages= 1–7| publisher = Wiley-VCH | location = Weinheim | doi = 10.1002/14356007.a07_017.pub2 |isbn=978-3527306732 }}

: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.{{cite web | url=https://publishing.cdlib.org/ucpressebooks/view?docId=ft5g500723&chunk.id=d0e3659&toc.depth=100&toc.id=d0e3589&brand=ucpress | title=The Quiet Revolution }}

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,{{cite book | url = https://patentimages.storage.googleapis.com/6c/7c/d2/62398f0fc22989/US3517505.pdf | title = Method and apparatus for suppressing contrails | publisher = United States Patent and Trademark Office | year = 1970}} and to produce smoke screens.{{cite video | title = The Royal Navy at War | medium = DVD | publisher = Imperial War Museum | location = London | date = 2005}}{{cite web | url = https://www.bbc.com/news/science-environment-43727547 | title = Nazi legacy found in Norwegian trees | date = 2018-04-11 | publisher = BBC News Online | first = Jonathan | last = Amos | access-date = 2018-04-17}}

Safety

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

:ClSO₃H + H₂O → H₂SO₄ + HCl

Related halosulfuric acids

Fluorosulfonic acid, FSO₂OH, is a related strong acid with a diminished tendency to evolve hydrogen fluoride.
Bromosulfonic acid, BrSO₂OH, is unstable, decomposing at its melting point of 8 °C to give bromine, sulfur dioxide, and sulfuric acid.
Iodosulfonic acid is not known to occur.

References

Category:Oxohalides

Category:Reagents for organic chemistry

Category:Sulfur oxoacids

Category:Sulfuryl compounds

Category:Lachrymatory agents

Category:Superacids