Carbon Tetrachloride

Carbon tetrachloride It is a colorless liquid, with a slightly sweet odor, similar to the smell of ether and chloroform. Its chemical formula is CCl 4 , and it constitutes a covalent and volatile compound, the vapor of which has a higher density than that of air; It is not friendly to electricity nor is it flammable.It is found in the atmosphere, river water, sea and sea surface sediments. It is believed that the carbon tetrachloride present in red algae is synthesized by the same organism.

In the atmosphere it is produced by the reaction of chlorine and methane. Produced carbon tetrachloride enters the ocean, mainly through the marine air interface. It is estimated that its atmospheric flux => oceanic is 1.4 x 10 10 g / year, equivalent to 30% of the total carbon tetrachloride of the atmosphere.

Main characteristics

Carbon tetrachloride is produced industrially by thermal chlorination of methane, in which methane is reacted with chlorine gas at temperatures between 400 °C and 430 °C. A crude product is produced during the reaction, with hydrochloric acid as a byproduct.

It is also produced industrially by the carbon disulfide method. Chlorine and carbon disulfide are reacted at temperatures from 90 °C to 100 °C, using iron as a catalyst. Then, the raw product is subjected to calibration, neutralization and distillation.

CCl 4 among others has had many uses: solvent of fats, oils, varnishes, etc.; dry cleaning of clothes; Insecticide, agriculture and fungicide in fumigation and nylon manufacture. However, despite its great utility, its use has been rejected partly because of its high toxicity.In humans, it produces toxic effects on the skin, eyes and respiratory tract. But its most harmful effect is in the functioning of the central nervous system, liver and kidneys. Kidney damage is probably the main cause of death attributed to the toxic action of carbon tetrachloride.

structure

In the image you can see the structure of carbon tetrachloride, which is tetrahedral geometry. Note that the Cl atoms (green sphere) are oriented in the space around the carbon (black sphere) by stretching the tetrahedron.

In addition, it is worth noting that because all vertices of the tetrahedron are equal, the structure is symmetric; That is, no matter how the CCl molecule is rotated 4 , will always be the same. Then, since the green tetrahedron of CCl 4 is symmetric, resulting in the absence of a permanent dipole moment.Why? Because Cl–ClO bonds with respect to C are polar due to the greater electronegativity of Cl, these moments were canceled out vectorially . Therefore, it is an apolar chlorinated organic compound.

The carbon in CCl is fully chlorinated 4 , what is equivalent to a higher oxidation (carbon can form a maximum of four bonds with chlorine). This solvent does not lose electrons, it is monopolar (does not contain hydrogen), and it represents a means of transport and small storage of chlorine.

physical and chemical properties

Formula

CCL 4

molecular weight

153.81 g/mol.

physical appearance

It is a colorless liquid. It crystallizes as monoclinic crystals.

dirt

Presents the characteristic odor present in other chlorinated solvents. The odor is fragrant and somewhat sweet, similar to the smell of tetrachloroethylene and chloroform.

boiling point

170.1 toF (76.8 C) to 760 mmHg.

Melting point

-9F (-23ºC).

Solubility in water

It is poorly soluble in water: 1.16 mg/mL at 25ºC and 0.8 mg/mL at 20ºC. Why? Because water, a highly polar molecule, does not “feel” an affinity for carbon tetrachloride, which is apolar.

Solubility in organic solvents

Due to the symmetry of its molecular structure, carbon tetrachloride is a non-polar compound. Therefore, it is miscible with alcohol, benzene, chloroform, ether, carbon disulfide, petroleum ether, and naphtha. Similarly, it is soluble in ethanol and acetone.

density

In liquid state: 1.59 g/ml at 68 °F and 1.594 g/ml at 20 °C.

In the solid state: 1.831 g/ml at -186 C and 1.809 g/ml at -80 C.

Stability

Generally inertia.

corrosive action

Attaches to certain forms of plastics, rubbers and coatings.

ignition point

It is not considered very flammable, indicating an ignition point of less than 982 C.

auto ignition

982 °C (1800 °F; 1255 K).

vapor density

5.32 with respect to air, equal to 1 is taken as the reference value.

steam pressure

91 mmHg at 68 °F; 113 mmHg at 77 andF and 115 mmHg at 25C.

rot

In the presence of fire forms chloride and phosgene, strongly toxic compounds. Similarly, 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.

viscosity

2.03 x 10 -3 Pa s

odor threshold

21.4 ppm.

Refractive Index ( D)

1.4607.

Applications

chemical manufacturing

-It serves as a chlorinating agent and/or solvent in the manufacture of organic chlorine. Similarly, it interferes as a monomer in the formation of nylon.

-Rubber serves as a solvent in the manufacture of cement, soap and insecticides.It is used in the manufacture of chlorofluorocarbon propellants.

Not having a –C–H bond, carbon tetrachloride does not undergo free radical reactions, so it is a useful solvent for halogens, either as an elemental halogen or a halogenating reagent, such as N-bromicyanide.

manufacture of refrigerators

It was used in the production of chlorofluorocarbons, the refrigerant R-11, and trichlorofluoromethane, the refrigerant R-12. These refrigerants destroy the ozone layer, which is why they recommended stopping their use, in accordance with the recommendations of the Montreal Protocol.

fire suppression

In the early 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 heated, carbon tetrachloride becomes a heavy vapor, which envelops the products of combustion, separating them from the oxygen present in the air and causing a fire. It is suitable for combating oil fires and equipment.

However, at temperatures above 500 °C, carbon tetrachloride may react with water to form phosgene, a toxic compound, so ventilation during use should be noted. In addition, it can react explosively with the metallic sodium, with the presence of this metal avoiding its use in fires.

clean

Carbon tetrachloride has been used in the dry cleaning of clothing and other materials for use in the home. In addition, it is used as an industrial corrosive of metals, excellent for dissolving grease and oil.

chemical analysis

It is used for the detection of boron, bromide, chloride, molybdenum, tungsten, vanadium, phosphorus and silver.

Infrared spectroscopy and nuclear magnetic resonance

-It is used as a solvent in infrared spectroscopy, as the carbon tetrachloride band does not have significant absorption at >1600 cm –1 .-It was used as a solvent in nuclear magnetic resonance, as it did not interfere with the technology as it did not contain hydrogen (it is unproductive). But because of its toxicity, and because its solvent power is low, carbon tetrachloride has been replaced by dilute solvents.

Thin

The characteristic of being a non-polar compound allows carbon tetrachloride to be used as a solvent for oils, fats, lacquers, varnishes, rubber waxes and resins. It can also dissolve iodine.

other uses

It is an important ingredient in lava lamps, because carbon tetrachloride adds weight to the wax due to its density.-Used by stamp collectors, as it reveals the watermark on stamps without causing damage.

To eliminate pests, it is used in insecticide, fungicide and spraying of cereals.

It is used as a lubricant in the metal cutting process.– It has been used in veterinary medicine as an anthelmintic in the treatment of fasciolasis, caused by Fasciola hepatica in sheep.

poisoning

-Carbon tetrachloride can be absorbed through the respiratory, digestive, ocular and skin routes. Ingestion and inhalation are very dangerous as they can cause serious long-term damage to the brain, liver and kidneys.

Contact with the skin causes irritation and in the long run it can cause a dermatitis. While contact with eyes causes irritation.

hepatotoxic mechanism

The main mechanisms that cause liver damage are oxidative stress and alteration of calcium homeostasis.

Oxidative stress creates an imbalance between the production of reactive oxygen species and the ability of the body to reduce the amount of oxygen that occurs within their cells, which regulates oxidative processes.

An imbalance in the normal redox state can lead to toxic effects by producing peroxides and free radicals that damage all components of cells.Carbon tetrachloride is metabolized to produce free radicals: Cl 3 C (radical trichloromethyl) and Cl3COO (radical trichloromethylperoxide). These free radicals cause lipoperoxidation, which also causes injury to the liver and lungs.

Free radicals also cause the breakdown of the plasma membrane of liver cells. It produces an increase in the cytosolic concentration of calcium and a decrease in the intracellular mechanism of calcium sequestration.

The intracellular increase of calcium activates the enzyme phospholipase A 2 It acts on the phospholipids of the membrane, enhancing its effect. In addition, there is infiltration of neutrophils and hepatocellular injury. There is a decrease in the cellular concentration of ATP and glutathione which causes enzymatic inactivation and cell death.

Toxic effects in the renal system and central nervous system

The toxic effects of carbon tetrachloride are manifested in the renal system with a decrease in urine and body water accumulation. Increased concentration of metabolic waste, especially in the lungs and in the blood. This can lead to death.

At the level of the central nervous system, there is participation of axonal conduction of nerve impulses.

effects of human exposure

a short time

eye irritation; Effects on the liver, kidneys and central nervous system, loss of consciousness may occur.

Long Term

Dermatitis and possible carcinogenic action.

toxic conversation

There is an association between several cases of intoxication with carbon tetrachloride and alcohol consumption. Excessive alcohol consumption damages the liver, producing liver cirrhosis in some cases.

It has been observed that the toxicity of carbon tetrachloride increases with barbiturates, as they have some of the same toxic effects.For example, at the level of the kidneys, barbiturates reduce urinary excretion, this action of barbiturates is similar to the toxic effect of carbon tetrachloride on kidney function.

intermolecular interactions

CCl 4 It can be considered as a green tetrahedron. How does it interact with others?

Being an apolar molecule, without a permanent dipole moment, it cannot interact by dipole-dipole forces. To hold its molecules together in a liquid, the chlorine atoms (the vertices of the tetrahedra) must interact with each other in some way; And they were successful thanks to the dispersal forces of London.

Electronic clouds of Cl atoms move, and for brief moments, generate rich and poor regions of electrons; That is, they immediately generate dipoles.

The rich field of electrons causes the – Cl atom of a neighboring molecule to become polarized: Cl – + Cl. Thus, two Cl atoms can be held together for a limited amount of time.

But, there are millions of CCl molecules 4 , the interaction becomes effective enough to form a liquid under normal conditions.In addition, the four Cs are covalently linked to each C, increasing the number of these interactions; So much so, that it boils at 76.8ºC, a high boiling point.

The boiling point of CCl can not be higher because the tetrahedra are relatively small compared to other apolar compounds (such as xylene, which boils at 144ºC).

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