Carbon disulfide

Carbon disulfide is a solvent for phosphorus, sulfur, selenium, bromine, iodine, fats, resins, rubber, and asphalt.[14]

For example, amines afford dithiocarbamates:[15]

2 R₂NH + CS₂ → [R₂NH₂⁺][R₂NCS₂⁻]

Xanthates form similarly from alkoxides:[15]

RONa + CS₂ → [Na⁺][ROCS₂⁻]

This reaction is the basis of the manufacture of regenerated cellulose, the main ingredient of viscose, rayon, and cellophane. Both xanthates and the related thioxanthates (derived from treatment of CS₂ with sodium thiolates) are used as flotation agents in mineral processing.

Upon treatment with sodium sulfide, carbon disulfide affords trithiocarbonate:[15]

Na₂S + CS₂ → [Na⁺]₂[CS₃²⁻]

Carbon disulfide does not hydrolyze readily, although the process is catalyzed by an enzyme carbon disulfide hydrolase.

Compared to the isoelectronic carbon dioxide, CS₂ is a weaker electrophile. While, however, reactions of nucleophiles with CO₂ are highly reversible and products are only isolated with very strong nucleophiles, the reactions with CS₂ are thermodynamically more favored allowing the formation of products with less reactive nucleophiles.[16]

Reduction of carbon disulfide with sodium affords sodium 1,3-dithiole-2-thione-4,5-dithiolate together with sodium trithiocarbonate:[17]

4 Na + 4 CS₂ → Na₂C₃S₅ + Na₂CS₃

Chlorination of CS₂ provides a route to carbon tetrachloride:[7]

CS₂ + 3 Cl₂ → CCl₄ + S₂Cl₂

This conversion proceeds via the intermediacy of thiophosgene, CSCl₂.

CS₂ is a ligand for many metal complexes, forming pi complexes. One example is CpCo(η²-CS₂)(PMe₃).[18]

Carbon disulfide insecticide ad from the 1896 issue of The American Elevator and Grain Trade magazine

It can be used in fumigation of airtight storage warehouses, airtight flat storage, bins, grain elevators, railroad box cars, ship holds, barges and cereal mills.[22] Carbon disulfide is also used as an insecticide for the fumigation of grains, nursery stock, in fresh fruit conservation and as a soil disinfectant against insects and nematodes.[23]

The primary source of carbon disulfide in the environment is rayon factories.[25] Most global carbon disulfide emissions come from rayon production, as of 2008.[28] Other sources include the production of cellophane, carbon tetrachloride,[28] carbon black, and sulfur recovery. Carbon disulfide production also emits carbon disulfide.[29]

As of 2004, about 250 g of carbon disulfide is emitted per kilogram of rayon produced. About 30 g of carbon disulfide is emitted per kilogram of carbon black produced. About 0.341 g of carbon disulfide is emitted per kilogram of sulfur recovered.[29]

Japan has reduced carbon disulfide emissions per kilogram of rayon produced, but in other rayon-producing countries, including China, emissions are assumed to be uncontrolled (based on global modelling and large-scale free-air concentration measurements). Rayon production is steady or decreasing except in China, where it is increasing, as of 2004.[29] Carbon black production in Japan and Korea uses incinerators to destroy about 99% of the carbon disulfide that would otherwise be emitted.[29] When used as a solvent, Japanese emissions are about 40% of the carbon disulfide used; elsewhere, the average is about 80%.[29]

Most rayon production uses carbon sulfide.[30][31] One exception is rayon made using the lyocell process, which uses a different solvent; as of 2018 the lyocell process is not widely used, because it is more expensive than the viscose process.[32][33] Cuprammonium rayon also does not use carbon disulfide.

Industrial workers working with carbon disulfide are at high risk. Emissions may also harm the health of people living near rayon plants.[25]

Concerns about carbon disulfide exposure have a long history.[21][34][35]^: 79 Around 1900, carbon disulfide came to be widely used in the production of vulcanized rubber. The psychosis produced by high exposures was immediately apparent (it has been reported with 6 months of exposure[25]). Sir Thomas Oliver told a story about a rubber factory that put bars on its windows so that the workers would not jump out to their deaths.[35]^: 17 Carbon disulfide's use in the US as a heavier-than-air burrow poison for Richardson's ground squirrel also led to reports of psychosis. No systematic medical study of the issue was published, and knowledge was not transferred to the rayon industry.[30]

The first large epidemiological study of rayon workers was done in the US in the late 1930s, and found fairly severe effects in 30% of the workers. Data on increased risks of heart attacks and strokes came out in the 1960s. Courtaulds, a major rayon manufacturer, worked hard to prevent publication of this data in the UK.[30] Average concentrations in sampled rayon plants were reduced from about 250 mg/m3 in 1955–1965 to about 20–30 mg/m3 in the 1980s (US figures only?).[25] Rayon production has since largely moved to the developing world, especially China, Indonesia and India.[31][30]

Rates of disability in modern factories are unknown, as of 2016.[31][36] Current manufacturers using the viscose process do not provide any information on harm to their workers.[30][31]