Carbon disulfide

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This article is about the chemical substance CS₂. For the software suite by Adobe Systems, see Adobe Creative Suite. For the cycle super-highway in London, see List of cycle routes in London.

Carbon disulfide

Carbon disulfide is a colorless volatile liquid with the formula CS₂. The compound is used frequently as a building block in organic chemistry as well as an industrial and chemical non-polar solvent. It has an "ether-like" odor, but commercial samples are typically contaminated with foul-smelling impurities.^[7]

Contents

 [hide] 

• 1 Occurrence and manufacture
• 2 Reactions
  • 2.1 Addition of nucleophiles
  • 2.2 Chlorination
  • 2.3 Coordination chemistry
  • 2.4 Carbon disulfide hydrolase
    • 2.4.1 Mechanism
• 3 Polymerization
• 4 Uses
  • 4.1 Fumigation
  • 4.2 Insecticide
  • 4.3 Solvent
  • 4.4 Manufacturing
  • 4.5 Working Fluid
  • 4.6 Spectroscope prisms
• 5 Health effects
• 6 See also
• 7 References
• 8 External links

Occurrence and manufacture[edit]

Small amounts of carbon disulfide are released by volcanic eruptions and marshes. CS₂ once was manufactured by combining carbon (or coke) and sulfur at high temperatures. A lower-temperature reaction, requiring only 600 °C, utilizes natural gas as the carbon source in the presence of silica gel or alumina catalysts:^[7]

2 CH₄ + S₈ → 2 CS₂ + 4 H₂S

The reaction is analogous to the combustion of methane. It is isoelectronic with carbon dioxide. CS₂ is highly flammable:

CS₂ + 3 O₂ → CO₂ + 2 SO₂

Global production/consumption of carbon disulfide is approximately one million tonnes, with China consuming 49%, followed by India at 13%, mostly for the production of rayon fiber.^[8] United States production in 2007 was 56,000 tonnes.^[9]

Reactions[edit]

Compared to CO₂, CS₂ is more reactive toward nucleophiles and more easily reduced. These differences in reactivity can be attributed to the weaker π donor-ability of the sulfido centers, which renders the carbon more electrophilic. It is widely used in the synthesis of organosulfur compounds such as metam sodium, a soil fumigant and is commonly used in the production of the soft fabric viscose.

Addition of nucleophiles[edit]

Nucleophiles such as amines afford dithiocarbamates:

2 R₂NH + CS₂ → [R₂NH₂⁺][R₂NCS₂⁻]

Xanthates form similarly from alkoxides:

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.

Sodium sulfide affords trithiocarbonate:

Na₂S + CS₂ → [Na⁺]₂[CS₃²⁻]

Chlorination[edit]

Chlorination of CS₂ is the principal route to carbon tetrachloride:^[7]

CS₂ + 3 Cl₂ → CCl₄ + S₂Cl₂

This conversion proceeds via the intermediacy of thiophosgene, CSCl₂.

Coordination chemistry[edit]

CS₂ is a ligand for many metal complexes, forming pi complexes. One example is CpCo(η²-CS₂)(PMe₃).^[10]

Carbon disulfide hydrolase[edit]

Carbon disulfide is naturally formed in the mudpots of volcanic solfataras. It serves as a source of hydrogen sulfide, which is an electron donor for certain organisms that oxidize it into sulphuric acid or related sulfur oxides. The hyperthermophilic Acidianus strain was found to convert CS₂ into H₂S and CO₂. The enzyme responsible for this conversion is termed carbon disulfide hydrolase.^[11]

The enzyme can be obtained in both apoenzyme and holoenzyme forms. The enzyme is predicted to have an isoelectric point of 5.92 and a molecular mass of 23,576 Da. The enzyme is hexadecameric.^[11]

The apoenzyme form, lacking the zinc cofactor, has a molecular weight of 382815.4 g/mol. The chloride ion and the 3,6,9,12,15,18,21,24,27,30,33,36,39-tridecaoxahentetracontane-1,41-diol (C28H58O15) are the two main ligands seen on the enzyme in this form. There are 16 polymer chains seen in this form contributing to the heaviness of the enzyme. This form is also sometimes termed the selenomethionine form.^[12]

CS₂ hydrolase in its holoenzyme has a cofactor bound to it. In this form the only ligand to be found is the zinc ion and the molecular weight of the enzyme overall is 189404.8 g/mol. There are only eight polymer chains seen in this form and this may be due to the fact that the enzyme catalyzes the conversion of CS₂ in this form.^[12]

The enzyme is similar to that of carbonic anhydrases. The enzyme monomer of CS₂ hydrolase displays a typical β-carbonic anhydrase fold and active site. Two of these monomers form a closely intertwined dimer with a central β-sheet capped by anα-helical domain. Four dimers form a square octameric ring through interactions of the long arms at the N and C termini. Similar ring structures have been seen in strains of carbonic anhydrases, however, in CS₂ hydrolase, two octameric rings form a hexadecamer by interlocking at right angles to each other. This results in the blocking of the entrance to the active site and the formation of a single 15-Å-long, highly hydrophobic tunnel that functions as a specificity filter. This provides a key difference between carbonic anhydrase and CS₂ hydrolase. This tunnel determines the enzyme's substrate specificity for CS₂, which is hydrophobic as well.

Mechanism[edit]

The mechanism by which this hydrolase converts CS₂ into H₂S is similar to that of how carbonic anhydrase hydrates CO₂ to HCO₃⁻.^{[citation needed]} This similarity points to a likely mechanism. The zinc at the active site is tetrahedral, being coordinated by Cys 35, His 88, Cys 91 and water.^{[citation needed]} The water is deprotonated to give a zinc hydroxide that adds the substrate to give a Zn-O-C(S)SH intermediate.^{[citation needed]} A similar process is proposed^{[by whom?]} to convert COS into CO2.^{[citation needed]}

CS₂ + H₂O → COS + H₂S

COS + H₂O → CO₂ + H₂S

Polymerization[edit]

CS₂ polymerizes upon photolysis or under high pressure to give an insoluble material called "Bridgman's black", named after the discoverer of the polymer, P. W. Bridgman. Trithiocarbonate (-S-C(S)-S-) linkages comprise, in part, the backbone of the polymer, which is a semiconductor.^[13]

Uses[edit]

Fumigation[edit]

It can be used in fumigation of airtight storage warehouses, airtight flat storages, bins, grain elevators, railroad box cars, shipholds, barges and cereal mills.^[14]

Insecticide[edit]

Carbon disulfide is used as an insecticide for the fumigation of grains, nursery stock, in fresh fruit conservation and as a soil disinfectant against insects and nematodes.^[15]

Solvent[edit]

Carbon disulfide is a solvent for phosphorus, sulfur, selenium, bromine, iodine, fats, resins, rubber, and asphalt.^[16] It has been used in the purification of single-walled carbon nanotubes.^[17]

Manufacturing[edit]

The principal industrial uses of carbon disulfide are the manufacture of viscose rayon, cellophane film, carbon tetrachloride and xanthogenates and electronic vacuum tubes.

Working Fluid[edit]

Various attempts were made in the 19th century to use carbon disulfide as the working fluid in steam engines and locomotive applications, due to its low boiling point; it would be either directly heated by the fuel, or would be used to recover waste heat from the combustion gases of other fuels and the condensing of steam in a traditional boiler. These experiments were never successful, both due to the low temperatures involved and the extreme risk of both poisoning and explosion.^[18]

Spectroscope prisms[edit]

Due to its high optical dispersion it was used in some spectroscopes.^[19]

Health effects[edit]

At high levels, carbon disulfide may be life-threatening because it affects the nervous system. Significant safety data comes from the viscose rayon industry, where both carbon disulfide as well as small amounts of H₂S may be present.

Carbon disulfide has been linked to toxin-induced parkinsonism. ^[20]

See also[edit]

• Carbon monosulfide
• Carbon subsulfide
• Carbon diselenide

출처: <https://en.wikipedia.org/wiki/Carbon_disulfide>