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.
Synthesis and reactions Thiobenzoic acid is prepared by treatment of benzoyl chloride with potassium hydrosulfide: 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. The conjugate base is thiobenzoate, C6H5COS−.
Oxidation of thiobenzoic acid gives the disulfide .
See also Dithiobenzoic acid
References