Dithiobenzoic acid

Dithiobenzoic acid is the organosulfur compound with the formula C₆H₅CS₂H. It is a dithiocarboxylic acid, an analogue of benzoic acid, but more acidic and deeply colored.

Dithiobenzoic acid

Names
Preferred IUPAC name Benzenecarbodithioic acid
Identifiers
CAS Number	121-68-6
3D model (JSmol)	Interactive image
ChemSpider	60487
ECHA InfoCard	100.004.084
EC Number	204-491-4
PubChem CID	67141
UNII	U9MSY3N8YB Y
CompTox Dashboard (EPA)	DTXSID0059532
InChI InChI=1S/C7H6S2/c8-7(9)6-4-2-1-3-5-6/h1-5H,(H,8,9) Key: ZGRWZUDBZZBJQB-UHFFFAOYSA-N
SMILES C1=CC=C(C=C1)C(=S)S
Properties
Chemical formula	C7H6S2
Molar mass	154.25 g·mol−1
Appearance	dark red sticky solid or viscous oil
Acidity (pKa)	1.92[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Synthesis and reactions

It can be prepared by sulfiding benzotrichloride:^[2]

C₆H₅CCl₃ + 4 KSH → C₆H₅CS₂K + 3 KCl + 2 H₂S

C₆H₅CS₂K + H⁺ → C₆H₅CS₂H + K⁺

It also arises by the reaction of the Grignard reagent phenylmagnesium bromide with carbon disulfide, followed by acidification:^[3]

C₆H₅MgBr + CS₂ → C₆H₅CS₂MgBr

C₆H₅CS₂MgBr + HCl → C₆H₅CS₂H + MgBrCl

It is about 100x more acidic than benzoic acid. Its conjugate base, dithiobenzoate, undergoes S-alkylation to give dithiocarboxylate esters.^[2] Similarly, dithiobenzoate reacts with "soft" metal salts to give complexes, e.g. Fe(S₂CC₆H₅)₃ and Ni(S₂CC₆H₅)₂.

Chlorination of dithiobenzoic acid gives the thioacyl chloride C₆H₅C(S)Cl.

Structure of the trimer [Ni(S₂CPh)₂]₃.^[4]

References

1. M. R. Crampton (1974). "Acidity and hydrogen-bonding". In Saul Patai (ed.). The Chemistry of the Thiol Group. Chichester: John Wiley & Sons Ltd. p. 402.
2. Frederick Kurzer; Alexander Lawson (1962). "Thiobenzoylthioglycolic Acid". Org. Synth. 42: 100. doi:10.15227/orgsyn.042.0100.
3. J. Houben (1906). "Ueber Carbithiosäuren. I. Arylcarbithiosäuren" [About Carbothioic Acids I. Arylcarbothioic Acids]. Berichte der Deutschen Chemischen Gesellschaft. 39 (3): 3219–3233. doi:10.1002/cber.190603903140.
4. Bonamico, M.; Dessy, G.; Fares, V.; Scaramuzza, L. (1975). "Structural Studies of Metal Complexes with Sulphur-Containing Bidentate Ligands. Part I. Crystal and Molecular Structures of Trimeric Bis-(dithiobenzoato)-nickel(II) and -palladium(II)". Journal of the Chemical Society, Dalton Transactions (21): 2250–2255. doi:10.1039/DT9750002250.