Tetrafluoromethane, also known as carbon tetrafluoride or R-14, is the simplest perfluorocarbon ( C F₄). As its IUPAC name indicates, tetrafluoromethane is the perfluorinated counterpart to the hydrocarbon

methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane ...

. It can also be classified as a

haloalkane The haloalkanes (also known as halogenoalkanes or alkyl halides) are alkanes containing one or more halogen substituents. They are a subset of the general class of halocarbons, although the distinction is not often made. Haloalkanes are widely u ...

halomethane Halomethane compounds are derivatives of methane () with one or more of the hydrogen atoms replaced with halogen atoms ( F, Cl, Br, or I). Halomethanes are both naturally occurring, especially in marine environments, and human-made, most notably ...

. Tetrafluoromethane is a useful refrigerant but also a potent

greenhouse gas A greenhouse gas (GHG or GhG) is a gas that absorbs and emits radiant energy within the thermal infrared range, causing the greenhouse effect. The primary greenhouse gases in Earth's atmosphere are water vapor (), carbon dioxide (), methane ...

. It has a very high bond strength due to the nature of the carbon–fluorine bond.

Bonding

Because of the multiple carbon–fluorine bonds, and the high

electronegativity Electronegativity, symbolized as , is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. An atom's electronegativity is affected by both its atomic number and the ...

fluorine Fluorine is a chemical element with the symbol F and atomic number 9. It is the lightest halogen and exists at standard conditions as a highly toxic, pale yellow diatomic gas. As the most electronegative reactive element, it is extremely reactiv ...

, the carbon in tetrafluoromethane has a significant positive partial charge which strengthens and shortens the four carbon–fluorine bonds by providing additional ionic character. Carbon–fluorine bonds are the strongest single bonds in

organic chemistry Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clayden, J ...

. Additionally, they strengthen as more carbon–fluorine bonds are added to the same carbon. In the one carbon

organofluorine compound Organofluorine chemistry describes the chemistry of the organofluorines, organic compounds that contain the carbon–fluorine bond. Organofluorine compounds find diverse applications ranging from oil and water repellents to pharmaceuticals, refr ...

s represented by molecules of

fluoromethane Fluoromethane, also known as methyl fluoride, Freon 41, Halocarbon-41 and HFC-41, is a non-toxic, liquefiable, and flammable gas at standard temperature and pressure. It is made of carbon, hydrogen, and fluorine. The name stems from the fact th ...

difluoromethane Difluoromethane, also called difluoromethylene, HFC-32 Methylene Fluoride or R-32, is an organic compound of the dihalogenoalkane variety. It has the formula of CH2F2. It is a colorless gas in the ambient atmosphere and is slightly soluble in t ...

, trifluoromethane, and tetrafluoromethane, the carbon–fluorine bonds are strongest in tetrafluoromethane. This effect is due to the increased coulombic attractions between the fluorine atoms and the carbon because the carbon has a positive partial charge of 0.76.

Preparation

Tetrafluoromethane is the product when any carbon compound, including carbon itself, is burned in an atmosphere of fluorine. With hydrocarbons,

hydrogen fluoride Hydrogen fluoride (fluorane) is an inorganic compound with the chemical formula . This colorless gas or liquid is the principal industrial source of fluorine, often as an aqueous solution called hydrofluoric acid. It is an important feedstock ...

is a coproduct. It was first reported in 1926. It can also be prepared by the

fluorination In chemistry, halogenation is a chemical reaction that entails the introduction of one or more halogens into a compound. Halide-containing compounds are pervasive, making this type of transformation important, e.g. in the production of polymers ...

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...

carbon monoxide Carbon monoxide ( chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simpl ...

phosgene Phosgene is the organic chemical compound with the formula COCl2. It is a toxic, colorless gas; in low concentrations, its musty odor resembles that of freshly cut hay or grass. Phosgene is a valued and important industrial building block, esp ...

with sulfur tetrafluoride. Commercially it is manufactured by the reaction of

with

dichlorodifluoromethane Dichlorodifluoromethane (R-12) is a colorless gas usually sold under the brand name Freon-12, and a chlorofluorocarbon halomethane (CFC) used as a refrigerant and aerosol spray propellant. Complying with the Montreal Protocol, its manufacture was ...

chlorotrifluoromethane Chlorotrifluoromethane, R-13, CFC-13, or Freon 13, is a non-flammable, non-corrosive chlorofluorocarbon (CFC) and also a mixed halomethane. It is a man-made substance used primarily as a refrigerant. When released into the environment, CFC-13 ha ...

; it is also produced during the

electrolysis In chemistry and manufacturing, electrolysis is a technique that uses direct electric current (DC) to drive an otherwise non-spontaneous chemical reaction. Electrolysis is commercially important as a stage in the separation of elements from n ...

of metal

fluoride Fluoride (). According to this source, is a possible pronunciation in British English. is an inorganic, monatomic anion of fluorine, with the chemical formula (also written ), whose salts are typically white or colorless. Fluoride salts ty ...

s MF, MF₂ using a carbon electrode. Although it can be made from a myriad of precursors and fluorine, elemental fluorine is expensive and difficult to handle. Consequently, is prepared on an industrial scale using

: :CCl₂F₂ + 2 HF → CF₄ + 2 HCl

Laboratory synthesis

Tetrafluoromethane and silicon tetrafluoride can be prepared in the laboratory by the reaction of

silicon carbide Silicon carbide (SiC), also known as carborundum (), is a hard chemical compound containing silicon and carbon. A semiconductor, it occurs in nature as the extremely rare mineral moissanite, but has been mass-produced as a powder and crystal s ...

with fluorine. : SiC + 4 F₂ → CF₄ + SiF₄

Reactions

Tetrafluoromethane, like other fluorocarbons, is very stable due to the strength of its carbon–fluorine bonds. The bonds in tetrafluoromethane have a bonding energy of 515 kJ⋅mol⁻¹. As a result, it is inert to acids and hydroxides. However, it reacts explosively with

alkali metal The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K),The symbols Na and K for sodium and potassium are derived from their Latin names, ''natrium'' and ''kalium''; these are still the origins of the names ...

Thermal decomposition Thermal decomposition, or thermolysis, is a chemical decomposition caused by heat. The decomposition temperature of a substance is the temperature at which the substance chemically decomposes. The reaction is usually endothermic as heat is re ...

or combustion of CF₄ produces toxic gases ( carbonyl fluoride and

) and in the presence of water will also yield

. It is very slightly soluble in water (about 20 mg⋅L⁻¹), but miscible with organic solvents.

Uses

Tetrafluoromethane is sometimes used as a low temperature

refrigerant A refrigerant is a working fluid used in the refrigeration cycle of air conditioning systems and heat pumps where in most cases they undergo a repeated phase transition from a liquid to a gas and back again. Refrigerants are heavily regulated ...

(R-14). It is used in

electronics The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons using electronic devices. Electronics uses active devices to control electron flow by amplification ...

microfabrication Microfabrication is the process of fabricating miniature structures of micrometre scales and smaller. Historically, the earliest microfabrication processes were used for integrated circuit fabrication, also known as " semiconductor manufacturing ...

alone or in combination with

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...

as a plasma etchant for

silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ...

silicon dioxide Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one ...

, and

silicon nitride Silicon nitride is a chemical compound of the elements silicon and nitrogen. is the most thermodynamically stable and commercially important of the silicon nitrides, and the term "silicon nitride" commonly refers to this specific composition. It ...

.K. Williams, K. Gupta, M. Wasilik. ''Etch Rates for Micromachining Processing – Part II'' J. Microelectromech. Syst., vol. 12, pp. 761–777, December 2003. It also has uses in neutron detectors.

Environmental effects

Tetrafluoromethane is a potent

that contributes to the

greenhouse effect The greenhouse effect is a process that occurs when energy from a planet's host star goes through the planet's atmosphere and heats the planet's surface, but greenhouse gases in the atmosphere prevent some of the heat from returning directly ...

. It is very stable, has an atmospheric lifetime of 50,000 years, and a high greenhouse warming potential 6,500 times that of CO₂. Tetrafluoromethane is the most abundant perfluorocarbon in the atmosphere, where it is designated as PFC-14. Its atmospheric concentration is growing. As of 2019, the man-made gases CFC-11 and CFC-12 continue to contribute a stronger

radiative forcing Radiative forcing (or climate forcing) is the change in energy flux in the atmosphere caused by natural or anthropogenic factors of climate change as measured by watts / metre2. It is a scientific concept used to quantify and compare the extern ...

than PFC-14. Although structurally similar to chlorofluorocarbons (CFCs), tetrafluoromethane does not deplete the ozone layer because the carbon–fluorine bond is much stronger than that between carbon and chlorine. Main industrial emissions of tetrafluoromethane besides hexafluoroethane are produced during production of

aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...

using Hall-Héroult process. CF₄ also is produced as product of the breakdown of more complex compounds such as

halocarbon Halocarbon compounds are chemicals in which one or more carbon atoms are linked by covalent bonds with one or more halogen atoms (fluorine, chlorine, bromine or iodine – ) resulting in the formation of organofluorine compounds, organochlor ...

Health risks

Due to its density, tetrafluoromethane can displace air, creating an

asphyxiation Asphyxia or asphyxiation is a condition of deficient supply of oxygen to the body which arises from abnormal breathing. Asphyxia causes generalized hypoxia, which affects primarily the tissues and organs. There are many circumstances that can ...

hazard in inadequately ventilated areas.

References

External links

*
National Pollutant Inventory – Fluoride and compounds fact sheetData from Air LiquideVapor pressure graph at Air LiquideProtocol for measurement of tetrafluoromethane and hexafluoroethane from primary aluminium productionChemical and physical properties table

WebBook page for CF4
{{Authority control Nonmetal halides Perfluoroalkanes Halomethanes Refrigerants Greenhouse gases