- Structure
- Nomenclature
- Properties
- Physical state
- Molecular weight
- Melting or solidification point
- Boiling point
- Flashpoint
- Autoignition temperature
- Density
- Vapor pressure
- Solubility
- Chemical properties
- Obtaining
- Presence in nature
- Applications
- In the chemical industry
- In rayon and cellophane production
- In the production of carbon tetrachloride
- In various applications
- Ancient uses
- Risks
- References
The carbon disulfide is a compound formed by the union of a carbon atom (C) and two sulfur atoms (S). Its chemical formula is CS 2. It is a colorless or slightly yellow liquid with an unpleasant odor due to the impurities it contains (sulfur compounds). When it is pure, its smell is soft and sweet, similar to chloroform or ether.
It originates naturally from the action of sunlight on organic molecules found in seawater. Furthermore, it is produced in swamp waters and is also expelled from volcanoes along with other gases.
Carbon disulfide CS 2. Author: Benjah-bmm27. Source: Wikimedia Commons.
Carbon disulfide is a volatile liquid and it is also highly flammable, so it should be kept away from flames and sparks or appliances that can produce them, even electric bulbs.
It has the ability to dissolve a large number of compounds, materials and elements, such as phosphorus, sulfur, selenium, resins, lacquers, etc. Therefore it finds utility as a solvent.
It is also an intermediary in various industrial chemical reactions, such as the production of rayon or artificial silk.
It must be handled with caution and with protective implements as it is very toxic and dangerous.
Structure
Carbon disulfide has one carbon atom and two sulfur atoms on the sides of it.
The bonds between the carbon atom and the sulfur atoms are covalent and double, therefore they are very strong. The CS 2 molecule has a linear and symmetric structure.
Linear structure of carbon disulfide CS 2. Black = carbon, yellow = sulfur. Author: Benjah-bmm27. Source: Wikimedia Commons.
Nomenclature
- Carbon disulfide
- Carbon bisulfide
- Dithiocarbon anhydride
Properties
Physical state
Colorless to yellowish liquid.
Molecular weight
76.15 g / mol
Melting or solidification point
-110.8 ° C
Boiling point
46.0 ºC
Flashpoint
-30 ºC (closed cup method).
Autoignition temperature
90 ° C
Density
Liquid = 1.26 g / cm 3 at 20 ºC.
Steam = 2.67 times that of air.
Its vapors are more than twice as heavy as air and the liquid is heavier than water.
Vapor pressure
279 mmHg at 25 ° C.
This is a high vapor pressure.
Solubility
Very slightly soluble in water: 2.16 g / L at 25 ° C. Soluble in chloroform. Miscible with ethanol, methanol, ether, benzene, chloroform, and carbon tetrachloride.
Chemical properties
CS 2 evaporates easily at room temperature as its boiling point is very low and its vapor pressure is very high.
Carbon disulfide is extremely flammable. Its vapors ignite very easily, even with the heat of an electric light bulb. This means that it reacts with oxygen very quickly:
CS 2 + 3 O 2 → CO 2 + 2 SO 2
The fact that it has a high vapor pressure at room temperature makes it dangerous to be near a flame.
When heated to decomposition it can easily explode, emitting toxic gases of sulfur oxides. Above 90 ° C it ignites spontaneously.
It decomposes when stored for a long time. Attacks copper and its alloys. It also reacts with some plastics, rubbers, and coatings.
Reacts under certain conditions with water, forming OCS carbonyl sulfide, CO 2 carbon dioxide and H 2 S hydrogen disulfide:
CS 2 + H 2 O → OCS + H 2 S
CS 2 + 2 H 2 O → CO 2 + 2 H 2 S
With alcohols (ROH) in alkaline medium forms xanthates (RO-CS-SNa):
CS 2 + ROH + NaOH → H 2 O + RO – C (= S) –SNa
Obtaining
Carbon disulfide is prepared commercially by reacting sulfur with carbon. The process is carried out at temperatures of 750-900 ° C.
C + 2 S → CS 2
Instead of coal, methane or natural gas can also be used, and even ethane, propane and propylene have been used, in which case the reaction occurs at 400-700 ° C with high yield.
It can also be prepared by reacting natural gas with hydrogen sulfide H 2 S at a very high temperature.
Presence in nature
CS 2 is a natural product present in the atmosphere in very small amounts (traces). It is produced photochemically in surface waters.
The action of sunlight on certain compounds present in seawater such as cysteine (an amino acid) leads to the formation of carbon disulfide.
Carbon disulfide can be formed by the action of sunlight on some organic compounds present in sea water. Author: Pexels. Source: Pixabay.
It is also released naturally during volcanic eruptions and is found in small amounts over swamps.
We are normally exposed to breathing it in very small proportions and it is present in some foods. It is also found in cigarette smoke.
In the environment it is decomposed by sunlight. On the ground it moves through it. Some microorganisms in the soil break it down.
Applications
In the chemical industry
Carbon disulfide is an important chemical compound as it is used to prepare other chemicals. It can act as a chemical intermediate.
It is also used as a process solvent for example to dissolve phosphorus, sulfur, selenium, bromine, iodine, fats, resins, waxes, lacquers and gums.
It allows the manufacture of pharmaceutical products and herbicides, among others.
In rayon and cellophane production
With CS 2, xanthates are prepared, which are compounds used in the manufacture of rayon and cellophane.
To obtain artificial silk or rayon, cellulose is started, which is treated with alkali and carbon disulfide CS 2 and transformed into cellulose xanthate, soluble in alkali. This solution is viscous and is therefore called "viscous".
The viscose is forced through very small holes in an acid bath. Here the cellulose xanthate is transformed back into cellulose which is insoluble and long, shiny threads are formed.
The threads or filaments can be spun into a material known as rayon.
(1) Cellulose + NaOH → Alkali-cellulose
ROH + NaOH → RONa
(2) Alkali-cellulose + Carbon disulfide → Cellulose xanthate
RONa + S = C = S → RO – C (= S) –SNa
(3) Cellulose xanthate + Acid → Cellulose (filaments)
RO – C (= S) –SNa + Acid → ROH
Garments made of rayon, a fiber in which carbon disulfide participates. Tobias "ToMar" Maier. Source: Wikimedia Commons.
If the cellulose is precipitated by passing the xanthate through a narrow slot, the cellulose is regenerated in the form of thin sheets that make up the cellophane. This is softened with glycerol and is used as a protective film for objects.
Cellophane is made with the help of carbon disulfide. Author: Hans Braxmeier. Source: Pixabay.
In the production of carbon tetrachloride
Carbon disulfide reacts with chlorine Cl 2 to give carbon tetrachloride CCl 4, which is an important non-combustible solvent.
CS 2 + 3 Cl 2 → CCl 4 + S 2 Cl 2
In various applications
Carbon disulfide participates in the cold vulcanization of rubbers, serves as an intermediate in the manufacture of pesticides, and is used to generate catalysts in the oil industry and in the manufacture of paper.
Xanthates prepared with CS 2 are used in mineral flotation.
Ancient uses
CS 2 is a poison for living organisms. Formerly it was used to destroy pests such as rats, marmots and ants, pouring the liquid into any closed space in which these animals lived (burrows and ant hills).
When used for this purpose, the dense toxic vapors wiped out any living organism that was in the confined space.
It was also used as an anthelmintic for animals and to kill blowfly larvae from the stomach of horses.
In agriculture it was used as an insecticide and nematicide, to fumigate the soil, for fumigation of nurseries, granaries, silos and cereal mills. Railroad cars, ships and barges were also sprayed.
A farmer in 1904 spraying the soil with carbon disulfide to combat a pest of grape plants. Ölgemälde von Hans Pühringer, 1904. Source: Wikimedia Commons.
All these uses were prohibited due to the high flammability and toxicity of CS 2.
Risks
CS 2 is highly flammable. Many of their reactions can cause fire or explosion. Mixtures of its vapors with air are explosive. When ignited, it produces irritating or toxic gases.
Carbon disulfide must not be poured down the drains, as a mixture of CS 2 and air remains in the pipes that can cause an explosion if ignited by accident.
Its vapors spontaneously ignite on contact with sparks or hot surfaces.
Carbon disulfide severely irritates eyes, skin and mucous membranes.
If inhaled or ingested, it seriously affects the central nervous system, the cardiovascular system, the eyes, the kidneys and the liver. It can also be absorbed through the skin causing damage.
References
- US National Library of Medicine. (2020). Carbon disulfide. Recovered from pubchem.ncbi.nlm.nih.gov.
- Mopper, K. and Kieber, DJ (2002). Photochemistry and the Cycling of Carbon, Sulfur, Nitrogen and Phosphorus. In Biogeochemistry of Marine Dissolved Organic Matter. Recovered from sciencedirect.com.
- Meyer, B. (1977). Industrial Uses of Sulfur and Its Compounds. Carbon Disulfide. In Sulfur, Energy, and Environment. Recovered from sciencedirect.com.
- Pohanish, RP (2012). C. Carbon disulfide. In Sittig's Handbook of Toxic and Hazardous Chemicals and Carcinogens (Sixth Edition). Recovered from sciencedirect.com.
- Morrison, RT and Boyd, RN (2002). Organic Chemistry. 6th Edition. Prentice-Hall.
- Windholz, M. et al. (editors) (1983). The Merck Index. An Encyclopedia of Chemicals, Drugs, and Biologicals. Tenth Edition. Merck & CO., Inc.