Xanthates

Alkali metal dithiocarbonates ROC (= S) S ^- Me ⁺ and the complete esters of dithiocaric acid ROC (= S) SR ', unlike the dithiocaric acids themselves, are stable.

Salts of dithiocarbonic acid are solid crystalline substances with an unpleasant odor; the color of xanthates depends on the metal and hydrocarbon radical included in their composition. Alkaline earth metal xanthates are usually colored in light tones - from white to light yellow. Alkaline earth metal xanthates are readily soluble in water, lower alcohols and ketones, and acetonitrile . Solubility increases in the series: Hg ²⁺ , Ag ⁺ , Cu ⁺ , Co ³⁺ , Pb ²⁺ , Tl ²⁺ , Cd ²⁺ , Ni ²⁺ , Zn ²⁺ . Poorly soluble in alcohol and ether and well soluble in chloroform and methylene chloride .

When heated, S-methyldithiocarbonates cleave methyl mercaptan and carbon sulfide to form alkenes ( Chugaev’s reaction ):

RR'CHCH ₂ OC (= S) SCH ₃ → RR'CH = CH ₂ + CH ₃ SH + COS

Salts of dithiocarbonic acid are usually prepared by reacting the corresponding alcohol with carbon disulfide and alkali in a polar solvent:

ROH + CS ₂ + NaOH → ROC (= S) SNa + H ₂ O

In some cases, the use of methylsulfinyl carbanion MeSOCH ₂ gives the best results ^[2] . Complete dithiocarboxylic acid esters can be prepared by alkylation with an appropriate alkyl halide:

ROC (= S) SNa + R'I → ROC (= S) SR '+ NaI

The most large-capacity xanthate is viscose - cellulose xanthate used in the manufacture of viscose fiber . Alkyl alkanthogenates of alkali metals (in particular potassium butyl xanthogenate) are used in flotation enrichment of sulfide ores (for example, in the production of lead from boulangerite ).