HearLore
ListenSearchLibrary

Follow the threads

Every story connects to a hundred more

Topics
  • Browse all topics
  • Featured
  • Recently added
Categories
  • Browse all categories
  • For you
Answers
  • All answer pages
Journal
  • All entries
  • RSS feed
Terms of service·Privacy policy

2026 HearLore

Preview of HearLore

Free to follow every thread. No paywall, no dead ends.

ListenSearchLibrary

Adapted from Chlorofluorocarbon, licensed under CC BY-SA 4.0. Modified for audio. This HearLore entry is also licensed under CC BY-SA 4.0.

— Ch. 1 · Molecular Geometry And Volatility —

Chlorofluorocarbon.

~5 min read · Ch. 1 of 6
Carbon atoms in chlorofluorocarbons bond with tetrahedral symmetry, yet the fluorine and chlorine atoms differ greatly in size from hydrogen. This difference causes methane-derived CFCs to deviate from perfect geometric shapes. The physical properties of these compounds change based on the number and identity of halogen atoms present. They remain volatile but less so than their parent alkanes due to molecular polarity induced by the halides. Methane boils at negative 161 degrees Celsius while fluoromethanes boil between negative 51.7 and negative 128 degrees Celsius. Chloride is even more polarizable than fluoride, giving CFCs higher boiling points. Their polarity makes them useful solvents for industrial applications. Boiling points also make them suitable as refrigerants for cooling systems. Densities of CFCs are higher than corresponding alkanes because density correlates with the number of chlorides. Production usually starts from chlorinated methanes and ethanes through halogen exchange reactions.

Thomas Midgley Jr And Early Adoption

Prior to the 1920s, refrigerators used toxic gases like ammonia and sulfur dioxide as coolants. A series of fatal accidents involving leaking chloromethane prompted a collaborative effort between Frigidaire, General Motors, and DuPont. Thomas Midgley Jr. of General Motors synthesized the first chlorofluorocarbons during this period. The Frigidaire corporation received patent number 1,886,339 on the 31st of December 1928. In 1930, Midgley demonstrated these properties by inhaling a breath of gas and blowing out a candle before the American Chemical Society. By 1930, General Motors and Du Pont formed Kinetic Chemical Company to produce Freon. Over 8 million refrigerators utilizing R-12 were sold by 1935. Carrier began using R-11 in the world's first self-contained home air conditioning unit known as the atmospheric cabinet. Public health codes revised to designate CFCs as the only safe gases for public buildings. Peak annual sales reached over 1 billion USD with more than 1 million metric tonnes produced annually.

Chlorine Radicals And Ozone Destruction

The reaction responsible for ozone depletion involves photo-induced scission of a carbon-chlorine bond. Chlorine atoms behave differently from chlorine molecules and are long-lived in the upper atmosphere. These radicals catalyze the conversion of ozone into oxygen. Ozone absorbs UV-B radiation so its depletion allows high energy radiation to reach Earth's surface. Bromine atoms act even more efficiently as catalysts making brominated CFCs subject to regulation. One key feature of CFCs is their low reactivity which gives them lifespans exceeding 100 years. This longevity allows time to diffuse into the upper stratosphere. Sunlight ultraviolet radiation causes homolytic cleavage of the carbon-chlorine bond once there. James Lovelock detected widespread presence of CFC-11 over Ireland finding a mole fraction of 60 parts per trillion. He measured CFC-11 in both Arctic and Antarctic air samples during an expedition ending in 1973. Sherry Rowland and Mario Molina published research suggesting the connection between CFCs and ozone damage in 1974.

Montreal Protocol And Global Regulation

Diplomats in Montreal forged a treaty called the Montreal Protocol by 1987 responding to dramatic seasonal depletion over Antarctica. Twelve European Community nations agreed on the 2nd of March 1989 to ban production of all CFCs by the end of the century. Diplomats met in London in 1990 to strengthen the protocol calling for complete elimination of CFCs by 2000. Developing countries were scheduled to eliminate CFCs completely by 2010. Prices increased considerably because only recycled CFCs remained available to treaty adhering countries. The United Nations Environmental Programme reported illegal trade in ozone depleting substances in 2006. Estimates showed between 16,000 and 38,000 tonnes passed through black markets in the mid-1990s. China, India, and South Korea accounted for around 70% of global CFC production as of 2007. Public attention drew to an unknown place in east Asia where estimated 13,000 metric tons annually produced since about 2012 violated the protocol. DuPont reversed its stance in 1986 after new patents arrived and publicly condemned CFCs before the Montreal Protocol.

Infrared Absorption And Climate Impact

CFCs absorb infrared radiation preventing heat from escaping Earth's atmosphere creating a potent greenhouse effect. Their strongest absorption bands occur between 7.8 and 15.3 micrometers referred to as the atmospheric window. This region has relative transparency allowing unique susceptibility to radiation absorption. Low concentration of each individual CFC intensifies this super greenhouse effect compared to carbon dioxide. Carbon dioxide is close to saturation with high concentrations while CFC effects increase linearly with mass. NASA reported in 2018 that the ozone layer hole began recovering due to CFC bans. Research released in 2019 showed alarming increases pointing to unregulated use in China. Groups actively dispose of legacy CFCs to reduce atmospheric impact. In 2002 there were estimated 5,791 kilotons of CFCs in existing products like refrigerators and air conditioners. One-third of these are projected to be emitted over the next decade if no action taken.

Ocean Circulation Tracing Methods

Known history of CFC concentrations provides important constraints on ocean circulation patterns. CFCs dissolve in seawater at the surface and transport into the ocean interior. Their inert nature means concentration reflects convolution of atmospheric time evolution and ocean mixing processes. Entry into the ocean makes them useful transient tracers for estimating rates and pathways. Production restrictions in the 1980s stopped increasing atmospheric concentrations of CFC-11 and CFC-12. The ratio between CFC-11 and CFC-12 has steadily decreased making water dating problematic. Sulfur hexafluoride production increased rapidly since the 1970s as another inert gas tracer. Using CFCs with sulfur hexafluoride resolves water dating issues from decreasing CFC concentrations. Solubility measurements of CFC-11 and CFC-12 were previously measured by Warner and Weiss. Solubility increases with decreasing temperature at approximately 1 percent per degree Celsius. Partial pressure corresponds directly to year with same atmospheric time histories allowing age calculation.

Up Next

Montreal ProtocolOzone depletion

Continue Browsing

Ozone depletionAir pollutionPollutionAerosol propellantsBelgian inventionsChlorofluorocarbonsDuPontEnvironmental controversiesFirefightingGreenhouse gasesHalogenated solventsHeating, ventilation, and air conditioningRefrigerants

Common questions

Who synthesized the first chlorofluorocarbons and when was it done?

Thomas Midgley Jr. of General Motors synthesized the first chlorofluorocarbons prior to 1930 during a collaborative effort between Frigidaire, General Motors, and DuPont. The Frigidaire corporation received patent number 1,886,339 on the 31st of December 1928 for these compounds.

What year did Sherry Rowland and Mario Molina publish research linking CFCs to ozone damage?

Sherry Rowland and Mario Molina published research suggesting the connection between CFCs and ozone damage in 1974. This research identified that chlorine atoms behave differently from chlorine molecules and are long-lived in the upper atmosphere where they catalyze the conversion of ozone into oxygen.

When did twelve European Community nations agree to ban production of all CFCs by the end of the century?

Twelve European Community nations agreed on the 2nd of March 1989 to ban production of all CFCs by the end of the century. Diplomats met in London in 1990 to strengthen this protocol calling for complete elimination of CFCs by 2000.

How do chlorofluorocarbons absorb infrared radiation compared to carbon dioxide?

Chlorofluorocarbon absorption bands occur between 7.8 and 15.3 micrometers referred to as the atmospheric window which has relative transparency allowing unique susceptibility to radiation absorption. Low concentration of each individual CFC intensifies this super greenhouse effect compared to carbon dioxide because carbon dioxide is close to saturation with high concentrations while CFC effects increase linearly with mass.

What year did James Lovelock detect widespread presence of CFC-11 over Ireland?

James Lovelock detected widespread presence of CFC-11 over Ireland finding a mole fraction of 60 parts per trillion during an expedition ending in 1973. He measured CFC-11 in both Arctic and Antarctic air samples during that same period.

See all questions about Chlorofluorocarbon →

In this section

Loading sources

All sources