Chlorofluorocarbons in Chemistry Structure Properties and Environmental Effects

Do You Know Chlorofluorocarbons Meaning?

CFC stands for chlorofluorocarbon, which is an organic compound made up of carbon, fluorine, and chlorine. Hydrochlorofluorocarbons, or HCFCs, are CFCs that also contain hydrogen in place of one or more chlorines. CFCs are also known as Freons, a brand of Wilmington, Delaware-based E.I. du Pont de Nemours & Company. CFCs were first formulated in the 1930s as a refrigerant.

Chlorofluorocarbons chemical formula is CCl2F2.

What is CFC Gas?

Dichlorodifluoromethane is by far the most common example (R-12 or Freon-12) of CFC gas. Many CFCs have been used as refrigerants, propellants (in aerosols), and solvents. CFCs have been phased out under the Montreal Protocol because they lead to ozone depletion in the upper atmosphere, and they are being replaced by other materials such as hydrofluorocarbons (HFCs).

Chlorofluorocarbon Structure

Carbon in CFCs bonds with tetrahedral symmetry, much as in simpler alkanes. The methane-derived CFCs deviate from perfect tetrahedral symmetry because the fluorine and chlorine atoms vary greatly in size and effective charge from hydrogen and each other.

Properties of Chlorofluorocarbons

• Changes in the number and identity of the halogen atoms will alter the physical properties of CFCs and HCFCs. They are unpredictable in general, but not as much as their parent alkanes. The decreased volatility is due to the halides' induction of molecular polarity, which creates intermolecular interactions. Methane boils at 161 degrees Celsius, while fluoromethanes boil between 51.7 (CF2H2) and 128 degrees Celsius (CF4).

• Since chloride is more polarizable than fluoride, CFCs have even higher boiling points. CFCs are useful solvents due to their polarity, and their boiling points make them ideal as refrigerants. CFCs are less flammable than methane, in part because they have fewer C-H bonds, and in part, because the released halides, in the case of chlorides and bromides, quench the free radicals that keep flames going.

• CFCs have a higher density than their corresponding alkanes. In general, the number of chlorides is proportional to the density of these compounds.

Preparation of Chlorofluorocarbons CFCs

CFCs and HCFCs are usually made from chlorinated methanes and ethanes by halogen exchange. The synthesis of chlorodifluoromethane from chloroform is given below:

HCCl3 + 2 HF → HCF2Cl + 2 HCl

Applications of Chlorofluorocarbons

Due to their low toxicity, reactivity, and flammability, CFCs and HCFCs are used in a variety of applications. Every possible mixture of fluorine, chlorine, and hydrogen-based on methane and ethane has been studied, and the majority of them have been commercialized. As a precursor to tetrafluoroethylene, the monomer that is converted into Teflon, billions of kilograms of chlorodifluoromethane are produced each year. propellants in medical applications and degreasing solvents are only a few of the applications.

Chlorofluorocarbons and Ozone Depletion

• Because of their role in ozone depletion, CFCs were phased out under the Montreal Protocol.

• CFCs' atmospheric effects, on the other hand, are not limited to their position as ozone-depleting chemicals. Infrared absorption bands prevent heat from leaving the earth's atmosphere at that wavelength.  The strongest absorption bands from C-F and C-Cl bonds in CFCs are found in the spectral region 7.8–15.3 m, which is referred to as the "atmospheric window" because of the relative clarity of the atmosphere within this range.

• CFCs and other unreactive fluorine-containing gases such as perfluorocarbons, HFCs, HCFCs, bromofluorocarbons, SF6, and NF3 produce a "super" greenhouse effect due to the frequency of CFC absorption bands and the peculiar sensitivity of the atmosphere at wavelengths where CFCs (indeed all covalent fluorine compounds) absorb. The low concentration of each individual CFC amplifies this “atmospheric window” absorption. Since CO2 is close to saturation at high concentrations and has few infrared absorption bands, the greenhouse effect's sensitivity to changes in CO2 concentration is low; the temperature rise is approximately logarithmic.

• CFCs, on the other hand, have a low concentration that allows their effects to rise linearly with mass, making them greenhouse gases with a much higher potential to increase the greenhouse effect than CO2.

• To reduce the effect of legacy CFCs on the environment, groups are actively disposing of them.

• As a result of CFC bans, NASA stated in 2018 that the hole in the ozone layer has started to close.

Did You Know?

From the late 1800s to the end of World War II, carbon tetrachloride (CCl4) was used in fire extinguishers and glass "anti-fire grenades." Chloroalkanes have been used for fire control on military aircraft since the 1920s. Freon is a brand name for a group of CFCs that are mainly used as refrigerants, but also have applications in firefighting and as aerosol propellants. Bromomethane is a commonly used fumigant. Dichloromethane is an industrial solvent with a large range of applications. 

In the late 1920s, Thomas Midgley, Jr. improved the synthesis process and led the drive to use CFC as a refrigerant to replace harmful refrigerants including ammonia (NH3), chloromethane (CH3Cl), and sulfur dioxide (SO2). The following qualities were sought in a new refrigerant: low boiling point, low toxicity, and general non-reactivity. Midgley flamboyantly demonstrated all of these properties in a demonstration for the American Chemical Society in 1930, by inhaling a breath of the gas and using it to blow out a candle.