Salt that is a metal-thioate/O-esters of dithiocarbonate
Sodium salt of ethyl xanthate
Cellulose xanthate (orange)
Xanthate usually refers to a salt with the formula ROCS− 2M+ (R = alkyl; M+ = Na+, K+), thus they are the metal-thioate/O-esters of dithiocarbonate. The name xanthates is derived from Ancient Greekξανθόςxanthos, meaning “yellowish, golden”, and indeed most xanthate salts are yellow. They were discovered and named in 1823 by Danish chemist William Christopher Zeise. These organosulfur compounds are important in two areas: the production of cellophane and related polymers from cellulose and (in mining) for extraction of certain ores. They are also versatile intermediates in organic synthesis. Xanthate can also refer to the O,S-ester of xanthic acid. These esters have the structure ROC(=S)SR′.
Xanthate salts are produced by the treatment of an alcohol, alkali, and carbon disulfide. The process is called xanthation. In chemical terminology, the alkali reacts with the alcohol to produce an alkoxide, which is the nucleophile that adds to the electrophilic carbon center in CS2. Often the alkoxide is generated in situ by treating the alcohol with sodium or potassium hydroxide:
ROH + CS2 + KOH → ROCS2K + H2O
For example, sodium ethoxide gives sodium ethyl xanthate. Many alcohols can be used in this reaction. Technical grade xanthate salts are usually of 90–95% purity. Impurities include alkali-metal sulfides, sulfates, trithiocarbonates, thiosulfates, sulfites, or carbonates as well as residual raw material such as alcohol and alkali hydroxide. These salts are available commercially as powder, granules, flakes, sticks, and solutions are available.
Some commercially important xanthate salts include:
Rarely encountered, thioxanthates arise by the reaction of CS2 with thiolate salts. For example, sodium ethylthioxanthate has the formula C2H5SCS2Na. Dithiocarbamates are also related compounds. They arise from the reaction of a secondary amine with CS2. For example, sodium diethyldithiocarbamate has the formula (C2H5)2NCS2Na.
^Xu, Y.; Lay, J. P.; Korte, F. (1988). "Fate and effects of xanthates in laboratory freshwater systems". Bulletin of Environmental Contamination and Toxicology. 41 (5): 683–689. doi:10.1007/BF02021019. PMID3233367. S2CID2696850.