Xanthate

Xanthate is an obsolete term for salts of O -alkyl esters of dithiocarbonic as well as for services accessed from O, S- dialkyl ( xanthogenic, Alkylxanthogenate ). They are carbonic acid derivatives in which two oxygen atoms is replaced by sulfur. They contain R -O- R -O CSS or CSS R1 as a functional group.

Representation

Salt-like xanthates can be represented with carbon disulfide from alkoxides by reacting:

The esters obtained from the salts by alkylation:

Reactions

By pyrolysis of alkylated xanthogenates arise in the Chugaev reaction alkenes. Since the reaction mechanism - similar to decarboxylation - can be described with a cyclic transition state, the Chugaev reaction proceeds as stereochemically unique syn-elimination.

By Barton -McCombie reaction is converted into the xanthate an alcohol to then radically to defunctionalization him with tributyltin hydride or hexamethyldisilazane to the alkane.

Applications

Xanthates are used as anionic collectors in the flotation of lead and copper ores using.

Fibers based on cellulose can be used as a lining material in producing high quality textiles.

The preparation of fibers or films ( " Cellophane "), based on cellulose xanthate can be effected by the method. This reaction was patented in 1892 by Cross and Bevan, the first film production by re-precipitation of the cellulose phase in 1898 by Stearn. Here, the pulp is first treated with sodium hydroxide for several hours ( mercerization ). With the addition of carbon disulfide arise within two to three hours the xanthate; In this case, only a part of hydroxyl groups of the glucose units is esterified. Due to the formation of by-product sodium trithiocarbonate, the mass turns brown. This mass is then diluted by addition of further sodium hydroxide solution. The result is a colloidal, highly viscous brown solution ( " viscose solution "), which gave its name to the fuzzy end product: " viscose ". Spinning the viscous solution by forcing the filaments into a precipitation bath, sulfuric acid then provides again the cellulose, which is also known as " viscose silk " or rayon.