Thiobenzoic acid explained

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.

Thiobenzoic acid is prepared by treatment of benzoyl chloride with potassium hydrosulfide:^[1]

C₆H₅C(O)Cl + KSH → C₆H₅C(O)SH + KCl

Acidity

With a pK_a near 2.5, this acid is almost 100x more acidic than benzoic acid.^[2] The conjugate base is thiobenzoate, C₆H₅COS⁻.

See also

• Dithiobenzoic acid

Notes and References

1. Paul Jr.. Noble . D. S. . Tarbell . Thiobenzoic Acid . Organic Syntheses . 32 . 101 . 1952 . 10.15227/orgsyn.032.0101.
2. 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.