Dichlorodifluoromethane

C 1
Cl 2
F 2

Ball-and-stick Stick Space-filling

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5 atoms, 4 single bonds, tetrahedral.

IUPAC name: dichloro(difluoro)methane
Molar mass: 120.907(24) g/mol
Atoms: 5
Shape: tetrahedral
Polarity: polar
SMILES: C(F)(F)(Cl)Cl
InChIKey: PXBRQCKWGAHEHS-UHFFFAOYSA-N
PubChem CID: 6391

Made of

C Cl F

Structural formula of dichlorodifluoromethane. Each unlabelled corner is a carbon atom. It shows which atoms are joined to which, not the shape. The model above shows the shape.

Sold under trade names such as Freon 12, dichlorodifluoromethane once cooled refrigerators and car air conditioners and propelled spray cans. The US Environmental Protection Agency (EPA) lists this chlorofluorocarbon (CFC) as CFC-12. Two atoms of chlorine and two of fluorine are attached to its single carbon, as the IUPAC name dichloro(difluoro)methane spells out. That makes it an organochlorine and an organofluorine compound at once, with a molar mass of 120.91 g/mol. Industry made it from carbon tetrachloride and anhydrous hydrogen fluoride.

At room temperature it is a colourless gas with a faint ethereal odour, boiling at −29.8 °C. Its vapour is 4.2 times as dense as air, and a gas that heavy can collect in low-lying spaces and leave them short of oxygen. It does not burn, and it holds together when heated to as much as 550 °C. Water takes up little of it, 280 mg per litre at 25 °C.

Structure and bonding

Dichlorodifluoromethane has a carbon at the centre with two chlorines and two fluorines around it, and no hydrogen anywhere. In Ball-and-stick the four partners sit at the corners of a lopsided tetrahedron. The model’s computed geometry narrows F–C–F to 106.6° and widens Cl–C–Cl to 111.5°, calculated values rather than measured ones. Stick shows the computed bonds to fluorine, 1.36 Å, as visibly shorter than those to chlorine, 1.77 Å. Space-filling wraps the carbon in two large chlorine spheres and two smaller fluorine ones.

Each bond joins carbon, 2.55 on the Pauling scale of electronegativity (an atom’s pull on shared electrons), to a stronger puller: chlorine at 3.16, fluorine at 3.98. Shared electrons drift toward the more electronegative atom, which makes every bond polar, according to Chem1. The viewer does not draw this uneven sharing. How bond polarities combine is the subject of polarity; here they leave a dipole moment of 0.51 debye, according to the Hazardous Substances Data Bank (HSDB). Only a zero time-averaged dipole earns the word nonpolar, so the molecule is polar. With no hydrogen, its molecules cannot hydrogen-bond together.

Where it turns up

It worked as a refrigerant, an aerosol propellant, a blowing agent for foam plastics, a solvent and a film cleaner in photography. It also detected leaks, froze food by direct contact and chilled cocktail glasses, according to HSDB. It was once registered as an insecticide, though no product containing it is registered now. Among food additives it is classed as a freezing agent and a propellant.

In 1986 cars were its largest user, according to HSDB, with mobile air-conditioning taking 37 per cent. Blowing agents took 11 per cent, aerosols and retail food refrigeration 4 per cent each, home refrigerators 2 per cent, and 31 per cent went unallocated. US output was about 199,000 tonnes in 1972 and about 188,000 tonnes in 1988. Its use in new US car air conditioners ended in the mid-1990s, when tetrafluoroethane took its place.

Why it matters

Nothing in the lower atmosphere destroys it, so it drifts up to the stratosphere, on EPA’s account. There intense ultraviolet light breaks it apart and frees chlorine atoms that deplete ozone. Its lifetime in the atmosphere is 100 years, according to EPA. Its ozone-depletion potential (ODP), its harm to ozone set against an equal mass of CFC-11, is 1 under the Montreal Protocol. In a 2011 assessment by the World Meteorological Organization, the ODP is 0.82. Class I substances, which include the CFCs, have an ODP of 0.2 or higher.

The United States shut its uses down in stages. EPA and two other agencies banned CFC propellants in aerosol spray cans in March 1978. According to HSDB, its aerosol use was prohibited in 1979, bar a few specialised items. The Montreal Protocol came into force on 1 January 1989. EPA made recycling CFCs from car air conditioners compulsory in 1992 and in 1993 banned venting them during servicing and disposal of refrigerators and air conditioners. US production and import of CFCs ended on 1 January 1996.

Properties

Properties of dichlorodifluoromethane Molar mass summed from IUPAC/CIAAW 2024 standard atomic weights; formula, atom and bond counts and PubChem's molecular weight from PubChem CID 6391.
Property	Value	Unit	Source
Molecular formula (Hill order)	CCl₂F₂
Molar mass	120.907(24) g/mol	g/mol	IUPAC/CIAAW 2024
Carbon atoms	1
Chlorine atoms	2
Fluorine atoms	2
Bonds	4
PubChem molecular weight	120.91 g/mol	g/mol	PubChem

Safety

Dichlorodifluoromethane comes as a gas under pressure, and its container may explode if heated. Under Japan’s revised classification it may also cause drowsiness or dizziness and harm public health by destroying upper-atmosphere ozone. Decomposed by heat, it releases highly toxic phosgene, hydrogen chloride and hydrogen fluoride. The PubChem Laboratory Chemical Safety Summary gathers these classifications; the card from NIOSH, the US National Institute for Occupational Safety and Health, holds the workplace limits.

Questions

Why is a CFC-12 molecule tetrahedral?

Its one carbon atom has four electron pairs and shares all of them, two with chlorine atoms and two with fluorine atoms. The pairs point away from one another to keep their repulsion small, and with every pair shared, the atoms take up the same tetrahedral arrangement, on Chem1's account.

Is R-12 the same as Freon 12?

Yes, both name dichlorodifluoromethane. Refrigerant gas R 12 is its shipping name in the US hazardous-materials regulations. Freon 12 was one of several former trade names, with Propellant 12, Frigen 12, Arcton 12, Genetron 12 and Eskimon 12, according to the Hazardous Substances Data Bank (HSDB). To the US Environmental Protection Agency it is CFC-12.

Is CFC-12 a greenhouse gas?

Yes. With carbon dioxide, methane, nitrous oxide and CFC-11, it is one of five gases that supplied about 96 per cent of the warming influence of long-lived greenhouse gases in 2024, according to the US National Oceanic and Atmospheric Administration. Its global-warming potential is 10,900 in the Intergovernmental Panel on Climate Change's fourth assessment report and 10,200 in its fifth, according to the US Environmental Protection Agency. CFC emissions have fallen under global controls on production and trade.

Is Freon 12 toxic?

It can harm people in several ways, according to the Hazardous Substances Data Bank (HSDB). It can displace oxygen and cause asphyxiation, act as an anaesthetic on the central nervous system, cause frostbite as the liquid, and sensitise the heart to fatal rhythm disturbances. The body clears it quickly: nearly all is breathed out within the first hour, and very little is broken down.

Same shape (tetrahedral)

CCl₄ Carbon tetrachloride 5 atoms, 4 single bonds, tetrahedral.
CHCl₃ Chloroform 5 atoms, 4 single bonds, tetrahedral.
CH₂Cl₂ Dichloromethane 5 atoms, 4 single bonds, tetrahedral.
CH₄ Methane 5 atoms, 4 single bonds, tetrahedral.
H₂SO₄ Sulfuric acid 7 atoms, 6 bonds, tetrahedral.