Alkali xanthates

Selenium and tellurium dioxides react with alkali xanthates and dithiocarbamates to give xanthates and dithiocarbamates of selenium(IV) and tellurium(IV).1,2 Russell1 states that the product formed by sodium diethyldithio-carbamate and selenium dioxide sometimes appears as an equimolar mixture of selenium (II) dithiocarbamate and the corresponding bis(thiocarbamyl) disulfide, (R2NCS)2S2. The commercial selenium dithiocarbamates, prepared by the above-mentioned method, usually consist of such mixtures. The disulfide can, in most cases, be extracted from selenium (II) dithiocarbamate by means of cold benzene or chloroform. 

Xanthates and dithioearbamates of bivalent selenium and tellurium may be conveniently prepared3-5 by allowing sodium selenopentathionate or sodium telluropenta-thionate to react with alkali xanthates or dithiocar-bamates. The reactions are rapid and quantitative, and the products separate from the aqueous reaction mixtures in a high state of purity. 

Without additional reagents Alkali xanthates from alcohols... 

Without additional reagents Alkali xanthates from alcohols Prepn. of alkali alkoxides with alkali hydroxides... 

Rayon. Viscose rayon is obtained by reacting the hydroxy groups of cellulose with carbon disulfide in the presence of alkali to give xanthates. When this solution is poured (spun) into an acid medium, the reaction is reversed and the cellulose is regenerated (coagulated). 

Cleady, fiee sodium hydroxide in alkali ceUulose leaving the sluiiy presses causes problems in xanthation, and the presses have to be operated to rninirnize... 

Alkali metal xanthates are prepared in high yield from reaction of amyl alcohols with alkah metal hydroxide and carbon disulfide (39—42). The xanthates are useful as collectors in the flotation of minerals and have minor uses in vulcani2ation of mbber and as herbicides (39,41). 

Other Inorganic Compounds. Alkali—metal and ammonium teUuropentathionates (Te(S203)2), have been prepared. The S2O3 group can be replaced by ethyl xanthate or diethyl dithiocyanate. 

Table 3. Decomposition Temperatures of Alkali Metal Xanthates ...

Alkalies stabilize xanthate solutions somewhat and the solutions readily decompose at acidic pHs (26,27). With a lower alkyl xanthate, the... 

The alkali metal xanthates react with the lower alkylamines ia the presence of catalytic amounts of nickel or palladium salts to give dialkjdthionocarbamates (62) ... 

Alkali Metal Xanthates. The commercially available xanthates are prepared from various primary or secondary alcohols. The alkyl group varies from to and the alkah metal may be sodium or potassium. Not all of the commercially available alcohols ia the range are available as... 

A number of compounds of the types RBiY2 or R2BiY, where Y is an anionic group other than halogen, have been prepared by the reaction of a dihalo- or halobismuthine with a lithium, sodium, potassium, ammonium, silver, or lead alkoxide (120,121), amide (122,123), a2ide (124,125), carboxylate (121,126), cyanide (125,127), dithiocarbamate (128,129), mercaptide (130,131), nitrate (108), phenoxide (120), selenocyanate (125), silanolate (132), thiocyanate (125,127), or xanthate (133). Dialkyl- and diaryUialobismuthines can also be readily converted to secondary bismuthides by treatment with an alkali metal (50,105,134) ... 

Reaction of alkali cellulose with carbon disulphide to produce a cellulose xanthate which forms a lyophilic sol with caustic soda. This may be extruded into a coagulating bath containing sulphate ions which hydrolyses the xanthate back to cellulose. This process is known as the viscose process and is that used in the manufacture of rayon. 

The first step in the manufacture of the foil involves the production of alkali cellulose. This is then shredded and allowed to age in order that oxidation will degrade the polymer to the desired extent. The alkali cellulose is then treated with carbon disulphide in xanthating chums at 20-28°C for about three hours. 

When ethanol is replaced by cellulose, sodium cellulose xanthate is obtained this dissolves in aqueous alkali to give a viscous solution (viscose) from which either viscose rayon or cellophane can be obtained by adding acid to regenerate the (reconstituted) cellulose. Trithiocarbonates (CS3 "), dithiocarbonates (COS2 "), xanthates (CS2OR ), difhiocarbamates (CS2NR2 ) and 1,2-dithiolates have an extensive coordination chemistry which has been reviewed. ... 

Many alkali-metal xanthates are formed by direct xanthation of alcohols (23), but their chemistry is still vague. Acidification of the alkali-metal salts produces the unstable xanthic acids (24). 

The alkali-metal salts of the thioxanthates are formed by a method analogous to that used for xanthates. Alkali-metal mercaptides react with carbon disulfide to form thioxanthate salts (25)... 

The wastewater generated in the membrane cell and other process wastewaters in the cell are generally treated by neutralization.28 Other pollutants similar to those in mercury and diaphragm cells are treated in the same process stated above. Ion exchange and xanthate precipitation methods can be applied in this process to remove the metal pollutants, while incineration can be applied to eliminate some of the hydrocarbons. The use of modified diaphragms that resist corrosion and degradation will help in reducing the amount of lead, asbestos, and chlorinated hydrocarbon in the wastewater stream from the chlor-alkali industry.28... 

The synthesis of alkali metal xanthates from trimethylsilyl dithiocarboxylates and alkali metal fluorides317 has been described as convenient and useful for preparative purposes of metal complexes and organometallic derivatives. 

Viscose Also known as the Cross-Bevan-Beadle process. A process for making regenerated cellulose fibers. The product has been known by the generic name rayon since 1924. Cellulose, from cotton or wood, is first reacted with sodium hydroxide ( mercerization), yielding alkali cellulose. This is dissolved in carbon disulfide, yielding cellulose xanthate, which is dissolved in sodium hydroxide solution. Injection of this solution (known as viscose... 

The primary products obtained from 2-butanol are of mechanistic. significance and may be compared with other eliminations in the sec-butyl system 87). The direction of elimination does not follow the Hofmann rule 88) nor is it governed by statistical factors. The latter would predict 60% 1-butene and 40% 2-butene. The greater amount of 2-alkene and especially the unusual predominance of the cis-olefin over the trans isomer rules out a concerted cis elimination, in which steric factors invariably hinder the formation of cis-olefin. For example, the following ratios oicisjtrans 2-butene are obtained on pyrolysis of 2-butyl compounds acetate, 0.53 89, 90) xanthate, 0.45 (S7) and amine oxide, 0.57 86) whereas dehydration of 2-butanol over the alkali-free alumina (P) gave a cisjtrans ratio of 4.3 (Fig. 3). 

Cellulose is sometimes used in its original or native form as fibers for textile and paper, but is often modified through dissolving and reprecipitation or through chemical reaction. The xanthate viscose process, which is used for the production of rayon and cellophane, is the most widely used regeneration process. The cellulose obtained by the removal of lignin from wood pulp is converted to alkali cellulose. The addition of carbon disulfide to the latter produces cellulose xanthate. 

Cellulose (VIII) is spun into fiber or cast into film by using a chemical reaction to convert it into a soluble xanthate derivative (Turbak, 1988). This is achieved by treating cellulose with 18-20% aqueous sodium hydroxide solution at 25-30°C for about 0.5-1 h. Much of the sodium hydroxide is physically absorbed into the swollen polymer some of it may be in the form of cellulose alkoxides. The excess alkali is pressed out of the cellulose pulp and the mass aged to allow oxidative degradation of the polymer chains to the desired molecular weight. The alkali cellulose is then treated with carbon disulfide at about 30° C and the resulting mass dissolved in dilute sodium hydroxide to form the sodium... 

Strong caustic solutions penetrate the crystal lattice of alpha cellulose and produce an alkoxide called alkali, or soda, cellulose. Mercerized cotton is produced by aqueous extraction of the sodium hydroxide from alkali cellulose fibers. Cellulose ethers and cellulose xanthate are produced by reactions of alkyl halides or carbon disulfide, respectively, with the alkali cellulose. 

Several cellulose esters (qv) are prepared commercially. Cellulose xanthate [9032-37-5] is made by reaction of cellulose swollen in 8.5—12% sodium hydroxide solution (alkali cellulose [9081-58-7]) with carbon disulfide and is soluble in the alkaline solution in which it is made. When such a solution, termed viscose, is introduced into an acid bath, the cellulose xanthate decomposes to regenerate cellulose as rayon fibers or cellophane sheets (see FIBERS, REGENERATED CELLULOSICS). 

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