Thiobenzoic acid
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| Reference =
| Name =Thiobenzoic acid
| PIN = Benzenecarbothioic S-acid
| OtherNames = {{Unbulleted list
| Benzoyl thiol
| Monothiobenzoic acid
}}
| ImageFile = Thiobenzoic acid.svg
| ImageSize = 120px
| Section1 = {{Chembox Identifiers
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| CASNo = 98-91-9
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| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = GBG5RLO56N
| ChEBI =
| ChemSpiderID = 7136
| EINECS = 202-712-9
| EC_number = 202-712-9
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| Gmelin = 1071790
| InChI = 1S/C7H6OS/c8-7(9)6-4-2-1-3-5-6/h1-5H,(H,8,9)
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| PubChem = 7414
| RTECS = DH6839000
| SMILES = C1=CC=C(C=C1)C(=O)S
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| Section2 = {{Chembox Properties
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| Appearance = yellow liquid
| BoilingPt =
| BoilingPtC = 222
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| Density = 1.1775 g/cm3
| C=7 | H=6 | O=1 | S=1
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| MeltingPtC = 24
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| pKa = 2.48
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| Solubility = soluble
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| VaporPressure = 0.1
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| Section6 = {{Chembox Pharmacology
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| Section7 = {{Chembox Hazards
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| Section9 = {{Chembox Related
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Thiobenzoic acid is an organosulfur compound with molecular formula C6H5COSH. It is the parent of aryl thiocarboxylic acids. It is a pale yellow liquid that freezes just below room temperature. The structure of thiobenzoic acid has not been examined by X-ray crystallography but the 4-methyl derivative has been reported. The CC(O)SH group is planar with syn geometry. The C=O and C-S lengths are respectively 120 and 177 pm.{{cite journal |doi=10.1246/bcsj.20150348 |title=Crystal Structure of 4-Methylbenzenecarbothioic Acid and Computational Investigations of Benzenecarbochalcogenoic Acids (C6H5COEH and C6H5CEOH, e = S, Se, Te) |date=2016 |last1=Kato |first1=Shinzi |last2=Niyomura |first2=Osamu |last3=Ebihara |first3=Masahiro |last4=Guo |first4=Jing-Dong |last5=Nagase |first5=Shigeru |journal=Bulletin of the Chemical Society of Japan |volume=89 |issue=3 |pages=361–368 }}
Synthesis and reactions
Thiobenzoic acid is prepared by treatment of benzoyl chloride with potassium hydrosulfide:{{cite journal | first1= Paul Jr.|last1= Noble |first2= D. S. |last2= Tarbell | title = Thiobenzoic Acid |journal= Organic Syntheses | volume = 32 | pages = 101 | year = 1952 | doi = 10.15227/orgsyn.032.0101}}
:C6H5C(O)Cl + KSH → C6H5C(O)SH + KCl
With a pKa near 2.5, this acid is almost 100x more acidic than benzoic acid.Matthys J. Janssen "Carboxylic Acids and Esters" in PATAI's Chemistry of Functional Groups: Carboxylic Acids and Esters, Saul Patai, Ed. John Wiley, 1969, New York: pp. 705–764. {{doi|10.1002/9780470771099.ch15}} The conjugate base is thiobenzoate, C6H5COS−.
Oxidation of thiobenzoic acid gives the disulfide {{chem2|(C6H5C(O)S)2}}.{{cite journal |doi=10.1107/S0108270183008616 |title=Structure of dibenzoyldisulphane, C14H10O2S2 |date=1983 |last1=Rout |first1=G. C. |last2=Seshasayee |first2=M. |last3=Subrahmanyan |first3=T. |last4=Aravamudan |first4=G. |journal=Acta Crystallographica Section C Crystal Structure Communications |volume=39 |issue=10 |pages=1387–1389 |bibcode=1983AcCrC..39.1387R }}