How Does Tetrachloroethylene Impact Industry and Environment?
What is Tetrachloroethylene?
Tetrachloroethylene is an organic chemical compound with the molecular formula C2Cl4. It is also known as perchloroethylene. It is widely used as an agent for dry cleaning that’s why it is also known as ‘dry cleaning fluid’. In 1985, its worldwide production was 1million metric tons. It belongs to the halogen alkene family as it has carbon – carbon double bond and halogen atoms. Its IUPAC name is tetrachloroethene. In abbreviated form it can be written as PERC or PCE. It is a synthetic compound which was first synthesized an English Scientist Michael Faraday in 1821. He synthesized it by using hexachloroethane (C2Cl6).
Tetrachloroethylene is a chlorocarbon with the formula Cl2C=CCl2.
Chemical Formula of Tetrachloroethylene
Structure of Tetrachloroethylene
Each molecule of tetrachloroethylene is composed of two carbon atoms which are bonded by double covalent bonds and four chlorine atoms which are bonded with carbon atoms by single covalent bond as shown below in its structure –
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Properties of Tetrachloroethylene
Physical and Chemical Properties – Tetrachloroethylene shows following physical and chemical properties –
It is a colorless liquid organic halogen compound.
It has a sweet odor. People can detect its presence even at its 1ppm concentration.
Its molar mass is 165.8 g/mol.
It has clear colorless experience.
Its density is 1.622 g.cm-3.
Its melting point is -19 °C at 254 K.
Its boiling point is 121.1 °C at 394.2 K.
It is slightly soluble in water. 15mg of tetrachloroethene gets dissolved in 1 liter of water at 25 °C temperature.
It is denser than water.
It non flammable.
It is a covalent compound.
It works as a good solvent for organic compounds.
It is volatile and highly stable.
Reaction with water – It reacts with water and forms dichloromethane and oxygen. Reaction is given below –
C2Cl4 + 2H2O 🡪 2CH2Cl2 + O2
Tetrachloroethene Dichloromethane Oxygen
Reaction with alkali – It reacts with alkalis such as sodium hydroxide and forms formic acid and sodium chloride. Reaction is given below –
4NaOH + C2Cl4 🡪 2HCO2H + 4NaCl
Sodium hydroxide Formic acid Sodium chloride
Production of Tetrachloroethene
As discussed initially, it was 1st synthesized by thermal decomposition of hexachloroethane by English scientist Michael Faraday. Reaction is given below –
C2Cl6 🡪 C2Cl4 + Cl2
Hexachloroethane Tetrachloroethene Chlorine
Most of the tetrachloroethane is synthesized by chlorination of simple hydrocarbons at high temperature. In these reactions carbon tetrachloride, hydrogen chloride and hexachlorobutadiene etc. are obtained as byproducts.
Another method includes heating of 1,2-dichloroethane up to 400 °C with chlorine. It gives a high yield of tetrachloroethene compared to other methods. It is separated by distillation method. Hydrochloric acid is obtained as a byproduct. Chemical reaction is given below –
ClCH2CH2Cl + 3Cl2 → Cl2C=CCl2 + 4HCl
1,2-dichloroethane Tetrachloroethene
In the above reaction a mixture of potassium chloride and aluminium chloride or activated carbon can be used as catalysts for higher rate of reaction.
Uses of Tetrachloroethylene
Historically, it was used as an intermediate in the production of 1,1,1,2-Tetrafluoroethane and in the treatment of hookworm infestation. Presently, it is used for various purposes in many fields. Its few applications are listed below –
It is widely used for dry cleaning of fabrics. That’s why it is also known as dry cleaning fluid.
It is used as solvent for many organic materials in various reactions.
It is used to remove grease from metals parts of automotive and other metal industries.
It is used as a cleaning agent with other chlorocarbons as well.
It is used as one of the ingredients in paint strippers and spot removers.
It is used in aerosol preparations as well.
An apparatus used in physics to study neutrinos is called a neutrino detector in which tetrachloroethylene is used.
Its small quantities are used as a vermifuge.
Tetrachloroethylene Effects on Health and Environment
When it was 1st synthesized in 1821, after that its production increased till mid 90s but in late 90s its production started to decrease due to its toxic nature and environmental hazards. This is the reason, in 1976 its production was 320,000 metric tons in the US while by 1993 it dropped to 123,000 metric tons according to the report of the United States Environmental Protection Agency. Although reports of human injury are very rare while it is widely being used in the dry cleaning industry.
It can be carcinogenic to human beings. It has been classified as Group 2A carcinogen by the international agency for research on cancer.
It can enter into our body by not only inhalation but dermal exposure as well. It acts as a central nervous system depressant. It dissolves the fats of our skin and causes skin irritation.
In 2007, California’s Air Resources Board banned tetrachloroethylene usage in the dry cleaning industry due to its toxicity and carcinogenic nature. Its exposure increases the risk of Parkinson’s disease 9 times.
It causes diseases in animals as well. Studies show that it may cause liver tumors in mice and kidney tumors in male rats. At high temperatures above 315 °C , it oxidized into phosgene which is a highly poisonous gas.
Its chronic exposure has been found linked with acquired color vision deficiencies.
It is a common soil contaminant which comes into the soil through ground water and untreated water from the dry cleaning industry. It is very difficult to remove it from water and soil. It requires chemical treatment.
Its larger amount is released into air than soil and water. It is degraded by hydrolysis and produces phosgene, hydrogen chloride, carbon tetrachloride, carbon dioxide and carbon monoxide etc.
This ends our coverage on the topic “Tetrachloroethylene”. We hope you enjoyed learning and were able to grasp the concepts. We hope after reading this article you will be able to solve problems based on the topic. If you are looking for solutions of NCERT Textbook problems based on this topic, then log on to Vedantu website or download Vedantu Learning App. By doing so, you will be able to access free PDFs of NCERT Solutions as well as Revision notes, Mock Tests and much more.
FAQs on Tetrachloroethylene: Formula, Structure, Production & Applications
1. What is tetrachloroethylene and what is its chemical formula?
Tetrachloroethylene, also known by names like perchloroethylene (PCE), is a synthetic chlorinated hydrocarbon. It is a colourless, non-flammable liquid with a distinct, sweet odour. Its chemical formula is C₂Cl₄, indicating that each molecule consists of two carbon atoms joined by a double bond, with four chlorine atoms attached.
2. What are the common and IUPAC names for tetrachloroethylene?
The systematic IUPAC name for this compound is tetrachloroethene. However, in industrial and commercial settings, it is more commonly known by several other names, including:
- Perchloroethylene (PCE)
- Tetrachloroethylene
- "Perc"
3. How is tetrachloroethylene commercially produced?
The primary commercial method for producing tetrachloroethylene is through the high-temperature chlorinolysis of light hydrocarbons. In this process, simple hydrocarbons are reacted with excess chlorine at very high temperatures (500-700°C). This reaction forms a mixture of chlorinated compounds, and tetrachloroethylene is then separated from this mixture through distillation. An important intermediate, hexachloroethane (C₂Cl₆), is often formed, which thermally decomposes to yield the final product.
4. What are the main industrial applications of tetrachloroethylene?
Tetrachloroethylene is a highly effective solvent with several major industrial applications:
- Dry Cleaning: It is the most common solvent used in the dry cleaning industry because it can effectively remove stains like oil and grease without damaging most fabrics.
- Metal Degreasing: In the automotive and metalworking industries, it is used to remove grease, oil, and other contaminants from metal parts before surface treatments like painting or coating.
- Chemical Intermediate: It serves as a precursor in the chemical synthesis of other compounds, notably certain hydrofluorocarbons (HFCs) used as refrigerants.
5. How does the structure of tetrachloroethylene contribute to its properties as a solvent?
The effectiveness of tetrachloroethylene as a solvent is a direct result of its molecular structure (C₂Cl₄). The molecule is highly symmetrical and non-polar. Due to the symmetrical placement of the four electronegative chlorine atoms around the carbon-carbon double bond, the individual bond dipoles cancel out, leading to a molecule with no net dipole moment. This non-polar nature allows it to readily dissolve other non-polar substances like fats, oils, and greases, based on the chemical principle of "like dissolves like."
6. Why is tetrachloroethylene often preferred for dry cleaning over other solvents?
Tetrachloroethylene is a popular choice in the dry cleaning industry for several practical reasons:
- Non-flammability: Unlike many petroleum-based solvents, it is not flammable, which greatly increases operational safety.
- High Solvency: It possesses a strong ability to dissolve a wide variety of organic stains without causing most textiles to shrink or lose their colour.
- Stability and Reusability: It is a stable compound that can be recovered, purified, and reused multiple times in the dry cleaning cycle, making it an economically efficient choice.
- Optimal Boiling Point: Its boiling point of 121°C is ideal for cleaning effectively while also allowing it to be easily evaporated and removed from garments during the drying phase.
7. What are the key differences between tetrachloroethylene and trichloroethylene?
Although both are chlorinated solvents, tetrachloroethylene (PCE) and trichloroethylene (TCE) have important distinctions:
- Chemical Structure: PCE (C₂Cl₄) has four chlorine atoms and no hydrogen atoms. In contrast, TCE (C₂HCl₃) has three chlorine atoms and one hydrogen atom.
- Primary Application: PCE is primarily used for dry cleaning fabrics because it is less aggressive. TCE is a stronger solvent mainly used for heavy-duty metal degreasing.
- Stability: PCE is more chemically stable. TCE is more susceptible to degradation, especially in the presence of light and heat, which can produce corrosive acidic byproducts.
8. What are the environmental and health concerns associated with using tetrachloroethylene?
The use of tetrachloroethylene is associated with significant health and environmental risks. It is classified as a probable human carcinogen by major health agencies. Chronic exposure can cause damage to the central nervous system, liver, and kidneys. From an environmental standpoint, it is a dense liquid that can contaminate groundwater. It is persistent in soil and water because it degrades very slowly. Due to these issues, its use is heavily regulated, and there is a continuous effort to replace it with safer alternatives.
