Tetrafluoromethane

Tetrafluoromethane, also known as carbon tetrafluoride or R-14, is the simplest fluorocarbon (CF4). It has a very high bond strength due to the nature of the carbon–fluorine bond. It can also be classified as a haloalkane or halomethane. Tetrafluoromethane is a useful refrigerant but also a potent greenhouse gas.[3]

Tetrafluoromethane
Carbon-tetrafluoride-2D-dimensions
Carbon-tetrafluoride-3D-balls-B
Names
IUPAC names
Tetrafluoromethane
Carbon tetrafluoride
Other names
Carbon tetrafluoride, Perfluoromethane, Tetrafluorocarbon, Freon 14, Halon 14, Arcton 0, CFC 14, PFC 14, R 14, UN 1982
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.000.815
EC Number
  • 200-896-5
RTECS number
  • FG4920000
UNII
Properties
CF4
Molar mass 88.0043 g/mol
Appearance Colorless gas
Odor odorless
Density 3.72 g/l, gas (15 °C)
Melting point −183.6 °C (−298.5 °F; 89.5 K)
Boiling point −127.8 °C (−198.0 °F; 145.3 K)
0.005%V at 20 °C
0.0038%V at 25 °C
Solubility soluble in benzene, chloroform
Vapor pressure 3.65 MPa at 15 °C
106.5 kPa at −127 °C
5.15 atm-cu m/mole
1.0004823[1]
Viscosity 17.32 μPa·s[2]
Structure
Tetragonal
Tetrahedral
0 D
Hazards
Safety data sheet ICSC 0575
NFPA 704
Flash point Non-flammable
Related compounds
Other cations
Silicon tetrafluoride
Germanium tetrafluoride
Tin tetrafluoride
Lead tetrafluoride
Related fluoromethanes
Fluoromethane
Difluoromethane
Fluoroform
Related compounds
Tetrachloromethane
Tetrabromomethane
Tetraiodomethane
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Bonding

Because of the multiple carbon–fluorine bonds, and the high electronegativity of fluorine, 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.[4] Additionally, they strengthen as more carbon–fluorine bonds are added to the same carbon. In the one carbon organofluorine compounds represented by molecules of fluoromethane, difluoromethane, trifluoromethane, and tetrafluoromethane, the carbon–fluorine bonds are strongest in tetrafluoromethane.[5] 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.[5]

Preparation

Tetrafluoromethane is the product when any carbon compound, including carbon itself, is burned in an atmosphere of fluorine. With hydrocarbons, hydrogen fluoride is a coproduct. It was first reported in 1926.[6] It can also be prepared by the fluorination of carbon dioxide, carbon monoxide or phosgene with sulfur tetrafluoride. Commercially it is manufactured by the reaction of hydrogen fluoride with dichlorodifluoromethane or chlorotrifluoromethane; it is also produced during the electrolysis of metal fluorides MF, MF2 using a carbon electrode.

Although it can be made from myriad precursors and fluorine, elemental fluorine is expensive and difficult to handle. Consequently, CF
4
is prepared on an industrial scale using hydrogen fluoride:[3]

CCl2F2 + 2 HF → CF4 + 2 HCl

Laboratory synthesis

Tetrafluoromethane can be prepared in the laboratory by the reaction of silicon carbide 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 metals. Thermal decomposition or combustion of CF4 produces toxic gases (carbonyl fluoride and carbon monoxide) and in the presence of water will also yield hydrogen fluoride.

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 (R-14). It is used in electronics microfabrication alone or in combination with oxygen as a plasma etchant for silicon, silicon dioxide, and silicon nitride.[7] It also has uses in neutron detectors.[8]

Environmental effects

Tetrafluoromethane is a potent greenhouse gas that contributes to the greenhouse effect. It is very stable, has an atmospheric lifetime of 50,000 years, and a high greenhouse warming potential of 6500 (which is given for the first 100 years thereof, CO2 has a factor of 1); however, the low amount in the atmosphere restricts the overall radiative forcing effect.

Although structurally similar to chlorofluorocarbons (CFCs), tetrafluoromethane does not deplete the ozone layer. This is because the depletion is caused by the chlorine atoms in CFCs, which dissociate when struck by UV radiation. Carbon–fluorine bonds are stronger and less likely to dissociate. According to Guinness World Records Tetrafluoromethane is the most persistent greenhouse gas.

Main industrial emissions of tetrafluoromethane besides hexafluoroethane are produced during production of aluminium using Hall-Héroult process. CF4 also is produced as product of the breakdown of more complex compounds such as halocarbons.[9]

Health risks

Due to its density, tetrafluoromethane can displace air, creating an asphyxiation hazard in inadequately ventilated areas.

See also

References

  1. ^ Abjean, R.; A. Bideau-Mehu; Y. Guern (15 July 1990). "Refractive index of carbon tetrafluoride (CF4) in the 300-140 nm wavelength range". Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. 292 (3): 593–594. doi:10.1016/0168-9002(90)90178-9.
  2. ^ Kestin, J.; Ro, S.T.; Wakeham, W.A. (1971). "Reference values of the viscosity of twelve gases at 25°C". Transactions of the Faraday Society. 67. doi:10.1039/TF9716702308.
  3. ^ a b Siegemund, Günter; Schwertfeger, Werner; Feiring, Andrew; Smart, Bruce; Behr, Fred; Vogel, Herward; McKusick, Blaine (2002). "Fluorine Compounds, Organic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a11_349.
  4. ^ O'Hagan D (February 2008). "Understanding organofluorine chemistry and in cations. An introduction to the C–F bond". Chemical Society Reviews. 37 (2): 308–19. doi:10.1039/b711844a. PMID 18197347.
  5. ^ a b Lemal, D.M. (2004). "Perspective on Fluorocarbon Chemistry". J. Org. Chem. 69 (1): 1–11. doi:10.1021/jo0302556. PMID 14703372.
  6. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  7. ^ K. Williams, K. Gupta, M. Wasilik. Etch Rates for Micromachining Processing – Part II J. Microelectromech. Syst., vol. 12, pp. 761–777, December 2003.
  8. ^ "Low efficiency 2-dimensional position-sensitive neutron detector for beam profile measurement". doi:10.1016/j.nima.2004.09.020.
  9. ^ Jubb, Aaron M.; McGillen, Max R.; Portmann, Robert W.; Daniel, John S.; Burkholder, James B. (2015). "An atmospheric photochemical source of the persistent greenhouse gas CF4". Geophysical Research Letters. 42 (21): 9505–9511. doi:10.1002/2015GL066193. ISSN 0094-8276.

External links

Carbonyl fluoride

Carbonyl fluoride is a chemical compound with the formula COF2. This gas, like its analog phosgene, is colourless and highly toxic. The molecule is planar with C2v symmetry.

Carbon–fluorine bond

The carbon–fluorine bond is a polar covalent bond between carbon and fluorine that is a component of all organofluorine compounds. It is the fourth strongest single bond in organic chemistry—behind the B-F single bond, Si-F single bond and the H-F single bond, and relatively short—due to its partial ionic character. The bond also strengthens and shortens as more fluorines are added to the same carbon on a chemical compound. As such, fluoroalkanes like tetrafluoromethane (carbon tetrafluoride) are some of the most unreactive organic compounds.

Chlorotrifluoromethane

Chlorotrifluoromethane, R-13, CFC-13, or Freon 13, is a non-flammable, non-corrosive chlorofluorocarbon (CFC) and also a mixed halomethane. It is used as a refrigerant, however, due to concerns about its ozone-depleting potential, its use has been phased out due to the Montreal Protocol.

Climate change acronyms

The Intergovernmental Panel on Climate Change (IPCC) with the United Nations Framework Convention on Climate Change (UNFCCC) use tens of acronyms and initialisms in documents relating to climate change policy.

Dielectric gas

A dielectric gas, or insulating gas, is a dielectric material in gaseous state. Its main purpose is to prevent or rapidly quench electric discharges. Dielectric gases are used as electrical insulators in high voltage applications, e.g. transformers, circuit breakers (namely sulfur hexafluoride circuit breakers), switchgear (namely high voltage switchgear), radar waveguides, etc.

A good dielectric gas should have high dielectric strength, high thermal stability and chemical inertness against the construction materials used, non-flammability and low toxicity, low boiling point, good heat transfer properties, and low cost.The most common dielectric gas is air, due to its ubiquity and low cost. Another commonly used gas is a dry nitrogen.

In special cases, e.g., high voltage switches, gases with good dielectric properties and very high breakdown voltages are needed. Highly electronegative elements, e.g., halogens, are favored as they rapidly recombine with the ions present in the discharge channel. The halogen gases are highly corrosive. Other compounds, which dissociate only in the discharge pathway, are therefore preferred; sulfur hexafluoride, organofluorides (especially perfluorocarbons) and chlorofluorocarbons are the most common.

The breakdown voltage of gases is roughly proportional to their density. Breakdown voltages also increase with the gas pressure. Many gases have limited upper pressure due to their liquefaction.

The decomposition products of halogenated compounds are highly corrosive, hence the occurrence of corona discharge should be prevented.

Build-up of moisture can degrade dielectric properties of the gas. Moisture analysis is used for early detection of this.

Dielectric gases can also serve as coolants.

Vacuum is an alternative for gas in some applications.

Mixtures of gases can be used where appropriate. Addition of sulfur hexafluoride can dramatically improve the dielectric properties of poorer insulators, e.g. helium or nitrogen. Multicomponent gas mixtures can offer superior dielectric properties; the optimum mixtures combine the electron attaching gases (sulfur hexafluoride, octafluorocyclobutane) with molecules capable of thermalizing (slowing) accelerated electrons (e.g. tetrafluoromethane, fluoroform. The insulator properties of the gas are controlled by the combination of electron attachment, electron scattering, and electron ionization.Atmospheric pressure significantly influences the insulation properties of air. High-voltage applications, e.g. xenon flash lamps, can experience electrical breakdowns at high altitudes.

* the density is approximate; it is normally specified at atmospheric pressure, the temperature may vary, though it is mostly 0 °C.

Fluorocarbon

Fluorocarbons, sometimes referred to as perfluorocarbons or PFCs, are, strictly speaking, organofluorine compounds with the formula CxFy, i.e. they contain only carbon and fluorine, though the terminology is not strictly followed.

Compounds with the prefix perfluoro- are hydrocarbons, including those with heteroatoms, wherein all C-H bonds have been replaced by C-F bonds.

Fluorocarbons can be perfluoroalkanes, fluoroalkenes and fluoroalkynes and perfluoroaromatic compounds. Fluorocarbons and their derivatives are used as fluoropolymers, refrigerants, solvents, and anesthetics.

Halon

Halon may refer to:

Haloalkane, or halogenoalkane, a group of chemical compounds consisting of alkanes with linked halogens (in particular, bromine-containing haloalkanes)

Halomethane fire extinguishing systems

Various compounds that have been used in agriculture, dry cleaning, fire suppression, and other applications.

Halon 10001 (iodomethane)

Halon 1001 (bromomethane)

Halon 1011 (bromochloromethane, CH2BrCl)

Halon 104 (carbon tetrachloride)

Halon 1103 (tribromofluoromethane)

Halon 112 (dichlorofluoromethane)

Halon 1201 (bromodifluoromethane)

Halon 1202 (dibromodifluoromethane)

Halon 1211 (bromochlorodifluoromethane, CF2ClBr)

Halon 122 (dichlorodifluoromethane)

Halon 1301 (bromotrifluoromethane, CBrF3)

Halon 14 (tetrafluoromethane)

Halon 242 (1,2-dichlorotetrafluoroethane)

Halon 2402 (dibromotetrafluoroethane, C2Br2F4)—used as a fire extinguisher

Halon 2600 (hexafluoroethane)

Halon (software), a mail transfer agent (MTA) program

Halonium ion

A halonium ion is any onium compound (ion) containing a halogen atom carrying a positive charge. This cation has the general structure R−+X−R′ where X is any halogen and no restrictions on R, this structure can be cyclic or an open chain molecular structure. Halonium ions formed from fluorine, chlorine, bromine, and iodine are called fluoronium, chloronium, bromonium, and iodonium, respectively. The cyclic variety commonly proposed as intermediates in electrophilic halogenation may be called haliranium ions, using the Hantzch-Widman nomenclature system.

Halotron I

Halotron I is a fire-extinguishing agent based on the raw material HCFC-123 (93%) mixed with tetrafluoromethane and argon as propellants.

Hexafluoroethane

Hexafluoroethane is a fluorocarbon counterpart to the hydrocarbon ethane. It is a non-flammable gas negligibly soluble in water and slightly soluble in alcohol.

IPCC list of greenhouse gases

This is a list of LLGHG (long-lived greenhouse gases) greenhouse gases as used by the IPCC TAR.

List of UN numbers 1901 to 2000

The UN numbers from UN1901 to UN2000 as assigned by the United Nations Committee of Experts on the Transport of Dangerous Goods.

R14

R14, R-14 or R.14 may refer to:

In science and academia

R14: Reacts violently with water, a risk phrase

Tetrafluoromethane, a refrigerant

AutoCAD, version R14

C battery, or "C cell"In military

Caudron R.14, a 1918 variant of World War I R.11 aircraft

R-14 Chusovaya, a Soviet IRBM and space launcher

USS R-14 (SS-91), a 1919 R-class coastal and harbor defense submarine of the United States NavyIn transportation

R14 (New York City Subway car)

Renault 14, compact French car from the 1970s and 1980s, also known as R14

R13–R14 (Rodalies de Catalunya), a regional rail line in Catalonia, Spain

Tetrafluoride

A tetrafluoride is a chemical compound with four fluorines in its formula.

Tetrafluoroammonium

The tetrafluoroammonium cation (also known as perfluoroammonium) is a positively charged polyatomic ion with chemical formula NF+4. It is equivalent to the ammonium ion where the hydrogen atoms surrounding the central nitrogen atom have been replaced by fluorine. Tetrafluoroammonium ion is isoelectronic with tetrafluoromethane CF4 and the tetrafluoroborate BF−4 anion.

The tetrafluoroammonium ion forms salts with a large variety of fluorine-bearing anions. These include the bifluoride anion (HF−2), tetrafluorobromate (BrF−4), metal pentafluorides (MF−5 where M is Ge, Sn, or Ti), hexafluorides (MF−6 where M is P, As, Sb, Bi, or Pt), heptafluorides (MF−7 where M is W, U, or Xe), octafluorides (XeF2−8), various oxyfluorides (MF5O− where M is W or U; FSO−3, BrF4O−), and perchlorate (ClO−4). Attempts to make the nitrate salt, NF4NO3, were unsuccessful because of quick fluorination: NF+4 + NO−3 → NF3 + FONO2.

Tetrafluoroborate

Tetrafluoroborate is the anion BF−4. This tetrahedral species is isoelectronic with tetrafluoroberyllate (BeF2−4), tetrafluoromethane (CF4), and tetrafluoroammonium (NF+4) and is valence isoelectronic with many stable and important species including the perchlorate anion, ClO−4, which is used in similar ways in the laboratory. It arises by the reaction of fluoride salts with the Lewis acid BF3, treatment of tetrafluoroboric acid with base, or by treatment of boric acid with hydrofluoric acid.

Tetrahalomethane

Tetrahalomethanes are fully halogenated methane derivatives of general formula CBrkCllFmInAtp, where:Tetrahalomethanes are on the border of inorganic and organic chemistry, thus they can be assigned both inorganic and organic names by IUPAC: tetrafluoromethane - carbon tetrafluoride, tetraiodomethane - carbon tetraiodide, dichlorodifluoromethane - carbon dichloride difluoride.

Each halogen (F, Cl, Br, I, At) forms a corresponding halomethane, but their stability decreases in order CF4 > CH4 > CCl4 > CBr4 > CI4 from exceptionally stable gaseous tetrafluoromethane with bond energy 515 kJ.mol−1 to solid tetraiodomethane, depending on bond energy.

Many mixed halomethanes are also known, such as CBrClF2.

Zyron

Zyron is a registered trademark for specialty gases marketed to the global electronics industry by DuPont.

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