Carbon Disulphide

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 solvent. It has an "ether-like" odor, but commercial samples are typically contaminated with foul-smelling impurities.^[1]

Occurrence and manufacture

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 kieselgel or alumina catalysts:^[1]

CH₄ + 1/2 S₈ → CS₂ + 2 H₂S

The reaction is analogous to the combustion of methane. Although it is structurally similar to carbon dioxide, CS₂ is highly flammable:

CS₂ + 3 O₂ → CO₂ + 2 SO₂

Reactions

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 Metham sodium, a soil fumigant.

Addition of nucleophiles

Nucleophiles such as amines afford dithiocarbamates:

2R₂NH + 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[CS₃^2-]

Reduction

Sodium reduces CS₂ to give the heterocycle "dmit^2-":^[2]

:3 CS₂ + 4 Na → Na₂C₃S₅ + Na₂S

Direct electrochemical reduction affords the tetrathiooxalate anion:^[3]

:2 CS₂ + 2e^- → C₂S₄^2-

Chlorination

Chlorination of CS₂ is the principal route to carbon tetrachloride:^[1]

CS₂ + 3 Cl₂ → CCl₄ + S₂Cl₂

This conversion proceeds via the intermediacy of thiophosgene, CSCl₂.

Coordination chemistry

CS₂ is a ligand for many metal complexes, forming pi complexes. One example is CpCo(η²-CS₂)(PMe₃).^[4]

Health effects

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

References

1. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
2. ^ Girolami, G. S.; Rauchfuss, T. B. and Angelici, R. J., Synthesis and Technique in Inorganic Chemistry, University Science Books: Mill Valley, CA, 1999.ISBN: 0935702482
3. ^ Jeroschewski, P. "Electrochemical Preparation of Tetraalkylammonium Salts of Tetrathiooxalic Acid" Zeitschrift für Chemie (1981), volume 21, 412.
4. ^ Werner, H. (1982). "Novel Coordination Compounds formed from CS₂ and Heteroallenes". Coordination Chemistry Reviews 43: 165-185. DOI:10.1016/S0010-8545(00)82095-0.

External links

National Pollutant Inventory: Carbon disulfide

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