xanthate

Xanthates are the salts and esters of a xanthic acid, ROC(=S)SH or O-esters of dithiocarbonic acid where R is any organic residue. The ethyl ester CH₃CH₂OC(=S)SH is also the parent compound xanthic acid. Many xanthates have a yellow colour, which gives the compound its name derived from xanthous, meaning yellow. IUPAC does not recommend the use of this term.

Xanthates can be produced by the reaction of an alcohol with sodium or potassium hydroxide and carbon disulfide. The major xanthates produced worldwide include:

• Sodium ethyl xanthate (SEX)
• Sodium isopropyl xanthate (SIPX)
• Sodium isobutyl xanthate (SIBX)
• Potassium amyl xanthate (PAX)

Commercially available xanthates are from technical grade only and usually at a 90-95% purity. The content of inorganic by-products in the final product varies depending on the exposure to air and reaction parameters. Alkali-metal sulfide, sulfate, trithiocarbonates, thiosulfate, sulfite or carbonate can be found. In addition, residual raw material such as alcohol and alkali hydroxide can exist. No general specifications for xanthates exist.

They can be obtained as powder, granules, flakes or sticks and are also available in solution. Main worldwide export are done from China under granules form.

Xanthates are used as flotation agents in mineral processing. They are intermediates in the Chugaev elimination. Xanthates are also used to control radical polymerisation under the RAFT process, also termed MADIX (macromolecular design via interchange of xanthates).

The reaction of cellulose with carbon disulfide (CS₂) in presence of sodium hydroxide (NaOH) gives sodium cellulose xanthate, which upon neutralization with sulfuric acid (H₂SO₄) gives a viscose rayon or cellophane paper (sellotape or scotch tape).

External links

• IUPAC definition
• MSDS Potassium xanthate
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