[Chemistry Class Notes] Freon Pdf for Exam

The Freon gas is a colourless, odourless, noninflammable, noncorrosive gas of low toxicity introduced as refrigerants in the 1930s. They also proved helpful as propellants for aerosols and in numerous technical applications. Freon (trademark) comprises several simple fluorinated aliphatic organic compounds utilized for commercial and industrial purposes. Apart from fluorine and carbon, Freons often include hydrogen, bromine, or chlorine. As such, Freons are chlorofluorocarbons (CFCs), hydrofluorocarbons (HCFCs) and related compounds.

The Freons in chemistry have meagre boiling points, low surface tension, and low viscosity, making them quite valuable refrigerants. They are incredibly stable and inert substances. The Freons do not pose a fire hazard and don’t give off a detectable odour while circulating through refrigerators and air conditioners. Dichlorodifluoridemethane (Freon 12), trichlorofluoromethane (Freon 11), chlorodifluoromethane (Freon 22), dichlorotetrafluoroethane (Freon 114), and trichlorotrifluoroethane (Freon 113) are the crucial members of the family.

The History of Freons

Frederic Swarts synthesized the first CFCs during the 1890s. By the late 1920s, a research team was curated by Charles Franklin Kettering in General Motors to substitute dangerous refrigerants like ammonia. Thomas Midgley, Jr, headed the group. In 1928, the team enhanced the synthesis of CFCs and demonstrated their utility, stability and non-toxicity. Kettering patented a refrigerating apparatus to use the gas; he issued it to Frigidaire, a wholly-owned subsidiary of General Motors. In 1930, General Motors and Du Pont formed Kinetic Chemicals to produce Freon. Their product was dichlorodifluoromethane and called “Freon-12”, “R-12”, or “CFC-12”. The number after the R is a refrigerant class number developed by DuPont to identify single halogenated hydrocarbons and other refrigerants besides halocarbons systematically.

Most CFCs’ uses are now banned or severely restricted by the Montreal Protocol of August 1987, as they are responsible for ozone depletion. Brands of Freon containing hydrofluorocarbons (HFCs) instead have replaced many uses, but they, too, are under strict control under the Kyoto Protocol, as they are deemed “super-greenhouse effect” gases.

Freon Formula

Du Pont introduced a naming system for CFCs as per the fluorine, hydrogen, and carbon atoms. The number that is farthest from the right is the number of fluorines. The second number from the right is the number of hydrogen plus one. Lastly, the third digit from the right is the number of carbons minus one. Thus, CHClF₂ is Freon 22, CCl₂F₂ is Freon 12, and likewise.

You have to specify which Freon formula you are asking for. CFCl₃, CF₂Cl₂ – these all are Freons.

You can understand the chemical formula of Freons by using the following method. 

Freon (no. of carbons-1) (no. of hydrogen+1) (no. of fluorine)

For example:-CFCl₃ Freon 11

Here, the number of carbon =1 and 1–1=0, so there is no requirement to put the number of hydrogen, zero and 0+1=1 number of fluorine=1.

Freon Gas Structure

Freons are insoluble in water, and their general chemical inertness is phenomenal. They stay stable in hot concentrated mineral acids and are unaffected by molten sodium. Thus, the Freon gas structure results from the solid C-F bonds that become shorter as the fluorine atom of carbon ratio increases. Hence, the C-F bond length is 1.29 angstroms CH₃F, 1.358 angstroms in CF₂, and so forth.

In the stratosphere, Freons die out when exposed to ultraviolet light. 

CCl₂F₂ (g) + uv rays ——> CF₂Cl(g) + Cl(g) and the chlorine atoms destroy the ozone layer. 

There are over 300 “Freon gases”. Some are CFCs, some are HCFCs, and many have no chlorine in them.

So “Freon” is a brand name and means nothing else. The correct term is “Refrigerant”, which can include nitrogen, propane, alcohol, and a whole plethora of other gasses.

Uses of Freons 

On account of their low boiling points and low viscosity, the uses of Freons are innumerable. The primary refrigerant uses include –

• Refrigerators

• Air-conditioning systems

Other uses of Freons are –

• Aerosol propellants

• Foam-blowing agents

• Solvents

• Glass chillers

• Polymer intermediates

Freons also have applications in the following areas –

• Fire extinguishers

• Anaesthetics

Besides, Freons have been used as inhalants by many teenagers and young adults. Inhalants are everyday legal substances which when inhaled intensely, give a high. People may inhale refrigerant gases, paint thinners, sprays, or gasoline to get a kick.

But the use of Freons has been banned in most countries due to the potential environmental and health effects of ozone depletion and the greenhouse effect.

Conclusion

Nowadays, Freons are banned by an international agreement, and everyone is looking for substitutes. The United States banned CFC production in 1977, and that ban continues. Non-ozone layer depleting alternatives of the compounds are hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons (HCFCs) such as CH₂FCF₃ (HFC 134a) and CHCl₂CF₃ (HCFC 123). In 1987, the Montreal Protocol asserted for decreasing CFCs, and a 1992 amendment to the treaty ended the production of CFC. By 1993, the emissions of CFC declined dramatically.

A total of 148 nations are now signatory to the Montreal Protocol, which calls for HCFCs to be slowly removed by 2020 and alternated with HFCs, containing no chlorine and a short lifetime. The illegal market of CFCs is of such proportion that ‘Scientific American’ has reported that the illegal trade of CFC is one of the biggest dangers to the ozone layer recovery.