What Are Chlorofluorocarbons? Structure, Preparation, and Applications
Chlorofluorocarbons (CFCs) are non-flammable, non-toxic substances that are partially or totally halogenated paraffin hydrocarbons with just hydrogen (H), carbon (C), fluorine (F), and chlorine (Cl). It is produced as volatile derivatives of methane (CH4), ethane (C2H6), and propane (C3H8). CFC full form is related to the name of atoms from which it is composed; it is a chlorofluorocarbon.
Many chlorofluorocarbons have been widely used as propellants in applications for aerosol, refrigerants and solvents. The manufacture of such compounds has been phased out under the Montreal Protocol as they contribute to the depletion of the ozone layer in the upper atmosphere. Because of this, CFCs are being replaced with other products such as hydrofluorocarbons (HFCs) that include R-410A and R-134a.
Preparation of Chlorofluorocarbons
Chlorofluorocarbons are generally prepared from chlorinated methanes and ethanes through the exchange of halogen. The synthesis reaction of chlorodifluoromethane from chloroform (CHCl3) is as follows.
CHCl3 + 2HF → HCF2Cl + 2HCl
Properties of Chlorofluorocarbons
Carbon in the CFCs makes bonding with tetrahedral symmetry. The Chlorofluorocarbons, which are derived from CH4, deviate from the geometry of perfectly shaped tetrahedral symmetry. Some of the properties of CFCs are given below.
Chlorofluorocarbons are competitively less volatile than their parent alkanes. The boiling point of CH4 (methane) is −1610C, whereas the boiling point of the chloromethane is between −51.7 0C (CF2H2) and −1280C (CF4).
The densities of chlorofluorocarbon used to be higher than its corresponding alkanes. The density of these compounds has correlated with the number of chlorides.
These are odourless, very less flammable and tasteless. These compounds are chemically stable.
These are competitively less flammable than methane (CH4), because of the presence of less Carbon and Hydrogen bonding.
Examples of CFCs
Some important CFCs examples are as follows.
CFC-11
CFC-11 is trichlorofluoromethane which is also termed freon-11 or R-11. It is a CFC. It is a faintly ethereal, sweetish-smelling and colourless liquid. It boils at room temperature. CFC-11 comes under substances that damage the protective ozone layer of the earth.
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CFC-12
CFC-12 is dichloridofluoromethane which is a colourless gas. CFC-12 is generally manufactured under the brand name Freon-12. Through the reaction of carbon tetrachloride (CCl4) with hydrogen fluoride (HF), dichlorodifluoromethane/CFC-12 can be prepared.
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Carbon Tetrachloride
Carbon tetrachloride has the chemical formula CCl4. It is a colourless liquid having a sweet type of smell that can be detected at low levels. At low temperatures, it is practically not flammable.
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1,1,1-trichloroethane
1,1,1-trichloroethane is also an organic compound that is popularly known as methyl chloroform. It is chloroalkane as it is derived from an alkane. This is also colourless like most of the CFCs and the sweet-smelling liquid. It was once produced industrially in large quantities for the purpose to use as a solvent.
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The Ozone Layer Depletion
There is a thin layer of ozone particles present in the stratosphere approximately 20 km to 30 km from the surface of the earth. The ozone layer absorbs the Ultraviolet traditions that come from the sun to the earth, and hence it protects everyone from exposure to deadly radiation of UV. An ozone molecule is composed of three oxygen atoms (O3). Life on Earth would be very difficult without the ozone layer in the atmosphere.
The harmful effects of the ozone layer on human health are observed as exposure to ozone can cause difficulty in breathing, coughing and shortness of breath. It can lead to worse health conditions such as asthma, damaged airways, emphysema, chronic bronchitis, asthma etc. Ozone can continue to damage the lungs even after symptoms have disappeared.
Some chemical compounds are depleting the ozone layer, which is very dangerous for living beings as well as for the environment. Chlorofluorocarbons (CFCs), halons and hydrofluorocarbons (HCFCs) are such compounds that destroy ozone in the upper atmosphere (stratosphere).
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The major cause of the depletion is halogenOzone. CFCs is a non-reactive compound, so it migrates to the stratosphere with the wind. The radiation coming from the sun breaks down the CFC molecules and produces free atoms of chlorine. These atoms further react with ozone (O3) and reduce it to O2. This is a cyclic process where the continuous breakdown of ozone molecules happens. The most severe depletion in the ozone layer has occurred in the south pole. It was first seen in Antarctica.
Do You Know?
Representatives of 24 countries in 1987 came together and met together in Montreal, Canada. They all agreed on a protocol called the Montreal Protocol to reduce the use of substances that are depleting the ozone layer. Besides this in the year 2016, a group of scientists brings out that the ozone layer is slowly healing, which is proof that the Montreal Protocol is successfully working. It is estimated that by the 21st century, the ozone hole of Antarctica will completely heal.
Conclusion
Chlorofluorocarbon is used for many purposes, but it is harmful to the environment as it depletes the ozone layer; hence, we should try to reduce the applications of CFCS that affect our environment.
FAQs on Chlorofluorocarbon: Key Concepts for Chemistry Students
1. What are chlorofluorocarbons (CFCs) and why were they widely used?
Chlorofluorocarbons, commonly known by the trade name Freon, are synthetic organic compounds containing carbon, chlorine, and fluorine atoms. They are derived from simple alkanes like methane and ethane. They became popular for commercial and industrial applications due to their desirable properties: they are largely non-toxic, non-flammable, and chemically stable in the lower atmosphere, making them safe for everyday use in consumer products.
2. What were the primary applications of chlorofluorocarbons before they were phased out?
Before international regulations restricted their use, CFCs were integral to several industries. Their main applications included:
- Refrigerants: Used in refrigerators, freezers, and air conditioning systems for vehicles and buildings.
- Propellants: Utilised in aerosol spray cans for products like deodorants, hairsprays, and insecticides.
- Blowing Agents: Employed in the production of polymer foams, such as styrofoam, for insulation and packaging materials.
- Solvents: Used for cleaning electronic components and degreasing metals due to their effectiveness in dissolving oils and greases.
3. What is the chemical structure of chlorofluorocarbons, with some common examples?
Chlorofluorocarbons are a type of haloalkane where all hydrogen atoms of a simple alkane have been replaced by chlorine and fluorine atoms. Their structure is based on a central carbon atom(s). Key examples as per the NCERT syllabus for 2025-26 include:
- Trichlorofluoromethane (CCl₃F): Also known as Freon-11 or CFC-11.
- Dichlorodifluoromethane (CCl₂F₂): Also known as Freon-12 or CFC-12, one of the most common refrigerants.
4. How exactly do chlorofluorocarbons cause the depletion of the stratospheric ozone layer?
The environmental damage from CFCs occurs through a catalytic cycle in the stratosphere. Here is the step-by-step mechanism:
- Transport: Due to their chemical stability, CFCs are not broken down in the lower atmosphere (troposphere) and slowly drift up to the stratosphere.
- Photodissociation: In the stratosphere, intense ultraviolet (UV) radiation from the sun breaks the weaker carbon-chlorine (C-Cl) bond in the CFC molecule, releasing a highly reactive chlorine free radical (Cl•).
- Ozone Destruction: This chlorine radical acts as a catalyst, attacking an ozone molecule (O₃) to form chlorine monoxide (ClO•) and an oxygen molecule (O₂).
- Catalyst Regeneration: The chlorine monoxide radical (ClO•) then reacts with an oxygen atom to release the chlorine radical (Cl•) again, which is free to destroy another ozone molecule.
Because the chlorine radical is regenerated, a single CFC molecule can destroy thousands of ozone molecules, significantly damaging the ozone layer.
5. Are chlorofluorocarbons still used today in India and globally?
The production and use of chlorofluorocarbons are now largely banned worldwide under the Montreal Protocol, an international treaty signed in 1987 designed to protect the ozone layer. While new products do not use CFCs, these chemicals can still be found in older, pre-ban equipment like refrigerators and air conditioners. Improper disposal of this equipment remains a source of CFC emissions. Modern appliances use alternatives like hydrochlorofluorocarbons (HCFCs) and, more commonly, hydrofluorocarbons (HFCs).
6. Why are CFCs so stable in the lower atmosphere but highly destructive in the stratosphere?
This difference in behaviour is due to the varying energy conditions in the atmosphere. In the troposphere (lower atmosphere), the strong C-Cl and C-F bonds in CFC molecules are not broken by the lower-energy visible sunlight or by reacting with other atmospheric gases. In the stratosphere, however, the CFCs are exposed to high-energy UV radiation from the sun. This UV radiation has enough energy to break the relatively weaker C-Cl bond, releasing the chlorine radical that initiates ozone destruction. The C-F bond is stronger and generally remains intact.
7. Besides ozone depletion, what other environmental impact do chlorofluorocarbons have?
In addition to being potent ozone-depleting substances, chlorofluorocarbons are also powerful greenhouse gases. They are highly effective at absorbing infrared radiation (heat) that is radiated from the Earth's surface, trapping it in the atmosphere and contributing to global warming. The Global Warming Potential (GWP) of CFCs is thousands of times higher than that of carbon dioxide (CO₂), meaning that even in small concentrations, they have a significant warming effect on the climate.
