The carbon tetrachloride it is a colorless liquid, with a slightly sweet odor, similar to the odor of ether and chloroform. Its chemical formula is CCl4, and it constitutes a covalent and volatile compound, whose vapor is of greater density than air; it is not a conductor of electricity nor is it flammable.
It is found in the atmosphere, river water, the sea, and sediments on the marine surface. The carbon tetrachloride present in red algae is thought to be synthesized by the same organism.
In the atmosphere it is produced by the reaction of chlorine and methane. Industrially produced carbon tetrachloride enters the ocean, primarily through the sea-air interface. Its atmospheric flow => oceanic has been estimated to be 1.4 x 1010 g / year, equivalent to 30% of the total carbon tetrachloride in the atmosphere.
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Carbon tetrachloride is produced industrially by thermal chlorination of methane, reacting methane with chlorine gas at a temperature between 400ºC to 430ºC. During the reaction a crude product is generated, with a by-product of hydrochloric acid.
It is also produced industrially by the carbon disulfide method. Chlorine and carbon disulfide are reacted at a temperature of 90 ° C to 100 ° C, using iron as a catalyst. Then the crude product is subjected to fractionation, neutralization and distillation.
The CCl4 It has had multiple uses, among others: solvent for fats, oils, varnishes, etc .; dry cleaning of clothes; pesticide, agricultural and fungicide fumigation and Nylon manufacturing. However, despite its great utility, its use has been partially discarded due to the high toxicity it presents..
In humans it generates toxic effects on the skin, eyes and respiratory tract. But its most damaging effects occur on the functioning of the central nervous system, liver and kidneys. Kidney damage is perhaps the leading cause of deaths attributed to the toxic action of carbon tetrachloride.
In the image you can see the structure of carbon tetrachloride, which is of tetrahedral geometry. Note that the Cl atoms (the green spheres) are oriented in the space around the carbon (black sphere) drawing a tetrahedron.
Likewise, it should be mentioned that since all the vertices of the tetrahedron are identical, the structure is symmetric; that is, no matter how the CCl molecule is rotated4, it will always be the same. So, since the green tetrahedron of CCl4 is symmetrical, it results in the absence of a permanent dipole moment.
Why? Because although the C-Cl bonds are polar in character due to the greater electronegativity of Cl with respect to C, these moments cancel out vectorly. Therefore, it is an apolar chlorinated organic compound..
Carbon is fully chlorinated in CCl4, which is equal to high oxidation (carbon can form a maximum of four bonds with chlorine). This solvent does not tend to lose electrons, is aprotic (does not have hydrogens), and represents a small means of transport and storage of chlorine..
CCl4
153.81 g / mol.
It is a colorless liquid. Crystallizes in the form of monoclinic crystals.
It has the characteristic odor present in other chlorinated solvents. The smell is aromatic and somewhat sweet, similar to the smell of tetrachlorethylene and chloroform.
170.1ºF (76.8ºC) at 760mmHg.
-9ºF (-23ºC).
It is poorly soluble in water: 1.16 mg / mL at 25 ºC and 0.8 mg / mL at 20 ºC. Why? Because water, a highly polar molecule, does not "feel" affinity for carbon tetrachloride, which is nonpolar..
Due to the symmetry of its molecular structure, carbon tetrachloride is a nonpolar compound. Therefore, it is miscible with alcohol, benzene, chloroform, ether, carbon disulfide, petroleum ether, and naphtha. Likewise, it is soluble in ethanol and acetone..
In liquid state: 1.59 g / ml at 68 º F and 1.594 g / ml at 20 ºC.
In solid state: 1.831 g / ml at -186 ºC and 1.809 g / ml at -80 ºC.
Generally inert.
Attacks some forms of plastics, rubbers, and coatings.
It is considered as low flammable, indicating the ignition point as less than 982 ºC.
982 ºC (1800 º F; 1255 K).
5.32 in relation to air, taken as a reference value equal to 1.
91 mmHg at 68 ° F; 113 mmHg at 77ºF and 115 mmHg at 25ºC.
In the presence of fire, it forms chloride and phosgene, a highly toxic compound. Likewise, under the same conditions it decomposes into hydrogen chloride and carbon monoxide. In the presence of water at high temperatures, it can cause hydrochloric acid.
2.03 x 10-3 Pa s
21.4 ppm.
1.4607.
-It intervenes as a chlorinating agent and / or solvent in the manufacture of organic chlorine. Likewise, it intervenes as a monomer in the manufacture of Nylon..
-Acts as a solvent in the manufacture of rubber cement, soap and insecticide.
-It is used in the manufacture of the propellant chlorofluorocarbon.
-As it does not have C-H bonds, carbon tetrachloride does not undergo free radical reactions, making it a useful solvent for halogenations, either by an elemental halogen or by a halogenating reagent, such as N-bromosuccinimide..
It was used in the production of chlorofluorocarbon, refrigerant R-11 and trichlorofluoromethane, refrigerant R-12. These refrigerants destroy the ozone layer, which is why their use was recommended to cease, in accordance with the recommendations of the Montreal Protocol..
At the beginning of the 20th century, carbon tetrachloride began to be used as a fire extinguisher, based on a set of properties of the compound: it is volatile; its vapor is heavier than air; it is not an electrical conductor and is not very flammable.
When carbon tetrachloride is heated it turns into a heavy vapor that covers the combustion products, isolating them from the oxygen present in the air and causing the fire to go out. It is suitable for fighting oil and appliance fires.
However, at temperatures higher than 500 ºC, carbon tetrachloride can react with water, causing phosgene, a toxic compound, so attention must be paid to ventilation during use. In addition, it can react explosively with metallic sodium, and its use in fires with the presence of this metal should be avoided..
Carbon tetrachloride has long been used in dry cleaning clothes and other household materials. In addition, it is used as an industrial metal degreaser, excellent for dissolving grease and oil.
Used for the detection of boron, bromide, chloride, molybdenum, tungsten, vanadium, phosphorus and silver.
-It is used as a solvent in infrared spectroscopy, since carbon tetrachloride does not have a significant absorption in bands> 1600 cm-1.
-It was used as a solvent in nuclear magnetic resonance, since it did not interfere with the technique as it did not have hydrogen (it is aprotic). But due to its toxicity, and its low solvent power, carbon tetrachloride has been replaced by deuterated solvents..
The characteristic of being a non-polar compound allows the use of carbon tetrachloride as a dissolving agent for oils, fats, lacquers, varnishes, rubber waxes and resins. It can also dissolve iodine.
-It is an important component in lava lamps, since carbon tetrachloride adds weight to the wax due to its density..
-Used by stamp collectors, it reveals watermarks on stamps without causing damage.
-It has been used as a pesticidal and fungicidal agent and in the fumigation of grains in order to eliminate insects.
-In the metal cutting process it is used as a lubricant.
-It has been used in veterinary medicine as an anthelmintic in the treatment of fasciolasis, caused by Fasciola hepatica in sheep..
-Carbon Tetrachloride can be absorbed through the respiratory, digestive, eye and skin routes. Ingestion and inhalation are very dangerous as they can cause severe long-term damage to the brain, liver and kidneys..
-Contact with the skin causes irritation and in the long term can cause dermatitis. While contact with the eyes causes irritation.
The main mechanisms that produce liver damage are oxidative stress and alteration of calcium homeostasis.
Oxidative stress is an imbalance between the production of reactive oxygen species and the body's ability to generate a reducing environment, within its cells, that controls oxidative processes..
The imbalance in the normal redox state can cause toxic effects due to the production of peroxides and free radicals that damage all the components of the cells..
Carbon tetrachloride is metabolized producing free radicals: Cl3C. (trichloromethyl radical) and Cl3COO. (trichloromethyl peroxide radical). These free radicals produce lipoperoxidation, which causes damage to the liver and also the lung.
Free radicals also cause the breakdown of the plasma membrane of liver cells. This produces an increase in the cytosolic calcium concentration and a decrease in the intracellular mechanism of calcium sequestration..
Increased intracellular calcium activates the enzyme phospholipase Atwo that acts on phospholipids of the membrane, aggravating its affectation. In addition, neutrophil infiltration and hepatocellular injury occurs. There is a decrease in the cellular concentration of ATP and glutathione that causes enzyme inactivation and cell death.
The toxic effects of carbon tetrachloride are manifested in the renal system with a decrease in the production of urine and the body accumulation of water. Especially in the lungs and an increase in the concentration of metabolic waste in the blood. This can cause death.
At the level of the central nervous system, there is involvement of axonal conduction of nerve impulses.
Irritation of the eyes; effects on the liver, kidney and central nervous system, which may lead to loss of consciousness.
Dermatitis and possible carcinogenic action.
There is an association between many of the cases of carbon tetrachloride poisoning and alcohol use. Excess alcohol intake causes liver damage, producing liver cirrhosis in some cases.
The toxicity of carbon tetrachloride has been observed to be increased with barbiturates, as they have some similar toxic effects..
For example, at the renal level, barbiturates decrease urine excretion, this action of barbiturates being similar to the toxic effect of carbon tetrachloride on kidney function..
The CCl4 it can be considered as a green tetrahedron. How do you interact with others?
Being an apolar molecule, without permanent dipole moment, it cannot interact through dipole-dipole forces. To hold their molecules together in the liquid, the chlorine atoms (the vertices of the tetrahedrons) must interact with each other in some way; and they do it thanks to the dispersal forces of London.
The electronic clouds of the Cl atoms move, and for brief moments, generate rich and poor areas of electrons; that is, they generate instantaneous dipoles.
The δ- electron-rich zone causes the Cl atom of a neighboring molecule to polarize: Clδ- δ+Cl. Thus, two atoms of Cl can be held together for a limited time..
But, since there are millions of CCl molecules4, the interactions become effective enough to form a liquid under normal conditions.
Furthermore, the four Cl covalently linked to each C considerably increases the number of these interactions; so much so that it boils at 76.8ºC, a high boiling point.
The boiling point of CCl4 it cannot be higher because tetrahedra are relatively small compared to other apolar compounds (like xylene, which boils at 144ºC).
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