Carbon disulfide, also known by its chemical formula CS₂, is a colourless, volatile liquid with a faintly sweet odor. It is composed of one carbon atom double‑bonded to two sulfur atoms. The compound belongs to the class of thiocarbonyl compounds and is the simplest dithiocarbonyl.
Chemical and Physical Properties
- Molecular formula: CS₂
- Molar mass: 76.14 g·mol⁻¹
- Density: 1.262 g·cm⁻³ at 20 °C
- Boiling point: 46.3 °C (115.3 °F)
- Melting point: –111.6 °C (–169 °F)
- Vapor pressure: 1 atm at 46.3 °C; approximately 0.03 atm at 25 °C
- Solubility: Slightly soluble in water (≈0.2 g L⁻¹ at 20 °C); miscible with many organic solvents such as benzene, chloroform, and ether.
- Flammability: Highly flammable; forms explosive mixtures with air over a wide concentration range (≈1–30 % v/v).
The molecule is linear, belonging to the D∞h point group, and exhibits strong Raman‑active C=S stretching vibrations.
Production
Industrial synthesis of carbon disulfide primarily follows the reaction of carbon (or coke) with sulfur vapour at elevated temperatures (≈600–1000 °C):
$$ \text{C (solid) + 2 S (vapor) → CS₂ (gas)} $$
Alternative routes include:
- Methane–sulfur processes, where methane reacts with elemental sulfur or sulfur vapour.
- Hydrogen sulfide carbonylation, where carbon monoxide reacts with hydrogen sulfide over a catalyst.
Historically, the “direct process” (carbon + sulfur) was the predominant method, especially in the early 20th century.
Industrial Uses
- Viscose (Rayon) Production: Carbon disulfide serves as a solvent in the dissolution of cellulose to form viscose, a precursor to regenerated cellulose fibers.
- Organic Synthesis: It is employed as a reagent for the preparation of xanthates, carbonothioates, and other sulfur‑containing compounds.
- Fumigant: Utilised in agricultural settings as a fumigant for grain storage, though its use has declined due to toxicity concerns.
- Rubber Processing: Functions as a plasticizer and accelerator in the manufacture of rubber products.
- Analytical Chemistry: Acts as a solvent in certain chromatography and spectroscopy applications because of its high polarity for sulfur‑containing analytes.
Safety and Environmental Aspects
- Toxicity: Carbon disulfide is neurotoxic and can cause central nervous system effects, cardiovascular abnormalities, and reproductive toxicity upon chronic exposure. Acute inhalation may produce headache, dizziness, and nausea.
- Occupational Exposure Limits: Many jurisdictions set permissible exposure limits (e.g., 10 ppm as an 8‑hour time‑weighted average in the United States).
- Environmental Impact: It is moderately volatile and can contribute to air pollution. In the atmosphere, CS₂ is oxidized to carbonyl sulfide (COS) and sulfur dioxide (SO₂), both of which have roles in acid rain formation.
- Fire Hazard: Due to its low flash point and high vapour pressure, carbon disulfide requires stringent fire‑prevention measures, including explosion‑proof equipment and proper ventilation.
Protective measures include use of respiratory protection, leak detection systems, and closed‑system handling.
Historical Context
Carbon disulfide was first prepared in 1822 by the French chemist Marcellin Berthelot through the reaction of carbon and sulfur. Its industrial importance rose sharply after the invention of the viscose process by Charles Cross, Edward Bevan, and Laurence H. Scott in the late 19th century, making CS₂ a critical raw material for the burgeoning rayon industry.
References
- G. A. Olah, Comprehensive Organic Chemistry, 1990.
- International Programme on Chemical Safety (IPCS), Carbon Disulfide – Fact Sheet, 2012.
- L. H. Anderson, Industrial Chemistry, 5th ed., 2001.
(All information reflects the current consensus in peer‑reviewed chemical literature and authoritative safety databases.)