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Dithiobenzoic acid

Dithiobenzoic acid is the organosulfur compound with the formula C<sub>6</sub>H<sub>5</sub>CS<sub>2</sub>H. It is a dithiocarboxylic acid, an analogue of benzoic acid, but more acidic and deeply colored.

Synthesis and reactions

It can be prepared by sulfiding benzotrichloride:

C<sub>6</sub>H<sub>5</sub>CCl<sub>3</sub> + 4 KSH → C<sub>6</sub>H<sub>5</sub>CS<sub>2</sub>K + 3 KCl + 2 H<sub>2</sub>S
C<sub>6</sub>H<sub>5</sub>CS<sub>2</sub>K + H<sup>+</sup> → C<sub>6</sub>H<sub>5</sub>CS<sub>2</sub>H + K<sup>+</sup>

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

C<sub>6</sub>H<sub>5</sub>MgBr + CS<sub>2</sub> → C<sub>6</sub>H<sub>5</sub>CS<sub>2</sub>MgBr
C<sub>6</sub>H<sub>5</sub>CS<sub>2</sub>MgBr + HCl → C<sub>6</sub>H<sub>5</sub>CS<sub>2</sub>H + MgBrCl

It is about 100x more acidic than benzoic acid. Its conjugate base, dithiobenzoate, undergoes S-alkylation to give dithiocarboxylate esters. Similarly, dithiobenzoate reacts with "soft" metal salts to give complexes, e.g. Fe(S<sub>2</sub>CC<sub>6</sub>H<sub>5</sub>)<sub>3</sub> and Ni(S<sub>2</sub>CC<sub>6</sub>H<sub>5</sub>)<sub>2</sub>.

Chlorination of dithiobenzoic acid gives the thioacyl chloride C<sub>6</sub>H<sub>5</sub>C(S)Cl.

References