Thiobenzoic acid

Thiobenzoic acid

Names
Preferred IUPAC name Benzenecarbothioic S-acid
Other names Benzoyl thiol Monothiobenzoic acid
Identifiers
CAS Number	98-91-9  Y
3D model (JSmol)	Interactive image
ChemSpider	7136
ECHA InfoCard	100.002.466
EC Number	202-712-9202-712-9
Gmelin Reference	1071790
PubChem CID	7414
RTECS number	DH6839000
UNII	GBG5RLO56N  Y
CompTox Dashboard (EPA)	DTXSID3059181
InChI InChI=1S/C7H6OS/c8-7(9)6-4-2-1-3-5-6/h1-5H,(H,8,9)
SMILES C1=CC=C(C=C1)C(=O)S
Properties
Chemical formula	C7H6OS
Molar mass	138.18 g·mol−1
Appearance	yellow liquid
Density	1.1775 g/cm3
Melting point	24 °C (75 °F; 297 K)
Boiling point	222 °C (432 °F; 495 K)
Solubility in water	soluble
Vapor pressure	0.1
Acidity (pKa)	2.48
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

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. ^[1]

Synthesis and reactions

Thiobenzoic acid is prepared by treatment of benzoyl chloride with potassium hydrosulfide: ^[2]

C₆H₅C(O)Cl + KSH → C₆H₅C(O)SH + KCl

With a pK_a near 2.5, this acid is almost 100x more acidic than benzoic acid. ^[3] The conjugate base is thiobenzoate, C₆H₅COS⁻.

Oxidation of thiobenzoic acid gives the disulfide (C₆H₅C(O)S)₂. ^[4]

See also

• Dithiobenzoic acid

References

1. Kato, Shinzi; Niyomura, Osamu; Ebihara, Masahiro; Guo, Jing-Dong; Nagase, Shigeru (2016). "Crystal Structure of 4-Methylbenzenecarbothioic Acid and Computational Investigations of Benzenecarbochalcogenoic Acids (C₆H₅COEH and C₆H₅CEOH, e = S, Se, Te)". Bulletin of the Chemical Society of Japan. 89 (3): 361–368. doi:10.1246/bcsj.20150348.
2. Noble, Paul Jr.; Tarbell, D. S. (1952). "Thiobenzoic Acid". Organic Syntheses. 32: 101. doi:10.15227/orgsyn.032.0101.
3. 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
4. Rout, G. C.; Seshasayee, M.; Subrahmanyan, T.; Aravamudan, G. (1983). "Structure of dibenzoyldisulphane, C14H10O2S2". Acta Crystallographica Section C Crystal Structure Communications. 39 (10): 1387–1389. Bibcode:1983AcCrC..39.1387R. doi:10.1107/S0108270183008616.