Tetrafluoroethylene is a chemical compound of carbon and fluorine with the chemical formula C 2 F 4 , one of the representatives of fluoroolefins - unsaturated organofluorine compounds .
| Tetrafluoroethylene | |
|---|---|
 | |
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| General | |
| Systematic name | Tetrafluoroethylene |
| Abbreviations | TFE, monomer 4 |
| Traditional names | Perfluoroethylene |
| Chem. formula | C 2 F 4 |
| Thermal properties | |
| T. melt. | -131.15 ° C |
| T. bale. | −76.5 ° C |
| Cr. point | temperature 33.3 ° C density: 5.72 kg / m 3 |
| Classification | |
| Reg. CAS number | 116-14-3 |
| PubChem | |
| Reg. EINECS number | |
| Smiles | |
| Inchi | |
| Chebi | |
| ChemSpider | |
Content
Physical and chemical properties
Tetrafluoroethylene is a heavy gas (almost 3.5 times heavier than air), without color and odor.
The tetrafluoroethylene molecule is flat, the internuclear distance CC is 1.33 ± 0.06 Å, the internuclear distance CF is 1.30 ± 0.02 Å, the angle between FCF bonds is 114 ± 3 ° [1] .
Tetrafluoroethylene is a monomer of many polymers ( plastics ), easily polymerizes and copolymerizes with almost all monomers: ethylene , propylene , vinylidene fluoride , trifluorochlorethylene and others, forming fluoroplasts often with unique properties [2] .
Tetrafluoroethylene Production
In laboratory conditions, tetrafluoroethylene is obtained by debromination of 1,2-dibromotetrafluoroethane with zinc [2] :
or depolymerization of polytetrafluoroethylene in a technical vacuum :
![{\displaystyle {\mathsf {[{\text{-}}CF_{2}{\text{-}}CF_{2}{\text{-}}]_{n}{\xrightarrow[{}]{600-700^{0}C;130-700\Pi a}}nCF_{2}{\text{=}}CF_{2}}}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/f4304d51e1451f45384c9a80c1290055eee544e5)
In the industry, tetrafluoroethylene is obtained by pyrolysis of chlorodifluoromethane ( chladone-22 ) [2] [3] :
It is believed that the pyrolysis process proceeds through the formation of intermediate difluorocarbene [4] :
The pyrolysis process is accompanied by the formation of a large number of by-products: hexafluoropropylene , octafluorocyclobutane and many others.
Physical Properties [2]
Standard Enthalpy of Education - −659.5 kJ / mol
Heat of Fusion 7.714 kJ / mol
Fire hazard [2]
Hazard Class 4.
Tetrafluoroethylene is a combustible gas. Auto-ignition temperature 190 ° C.
Pure tetrafluoroethylene is an explosive gas at a pressure above 0.25 MPa. In this case, explosive polymerization occurs. Explosion initiators: oxygen, peroxide compounds , metal oxides of variable valency.
Liquid tetrafluoroethylene has no detonation properties.
Chemical Properties
On a palladium catalyst, tetrafluoroethylene combines hydrogen to form 1,1,2,2- tetrafluoroethane [3] .
When illuminated with actinic light, tetrafluoroethylene is subjected to halogenation [2] [3] .
Under harsh conditions, tetrafluoroethylene burns in oxygen, forming tetrafluoromethane and carbon dioxide [2] .
At elevated temperatures, tetrafluoroethylene undergoes cyclodimerization to form octafluorocyclobutane [2] .
The pyrolysis of tetrafluoroethylene is accompanied by the formation of hexafluoropropylene . It is believed that the formation of hexafluoropropylene is based on the reactions of difluorocarbene [2] [4]
The production of an important fluorine-containing monomer - hexafluoropropylene [2] [3] [4] is based on the pyrolysis reaction of tetrafluoroethylene .
Tetrafluoroethylene is easily polymerized by a radical mechanism in the presence of any sources of radicals. The polymerization is carried out both in suspension and emulsion processes.
The resulting polytetrafluoroethylene is produced in the form of various grades: F-4, F-4PN-90; F-4PN-40; F-4PN-20; F-4D, etc. [5]
Tetrafluoroethylene enters into a radical copolymerization reaction with various monomers:
- with ethylene - fluoroplast-40 (F-40);
- with hexafluoropropylene - fluoroplast-4MB (F-4MB);
- with vinylidene fluoride - fluoroplast-42 (F-42) [5]
Toxicity
Tetrafluoroethylene is a vascular poison, irritates the mucous membranes of the eyes and respiratory organs, affects the central nervous system, causes pulmonary edema , and has a nephrotoxic effect [6] .
MPC p.z = 30 mg / m 3 ; MPC m. = 6 mg / m 3 ; MPC SS = 0.5 mg / m 3
See also
- Polytetrafluoroethylene
- Organofluorine compounds
- Chlorodifluoromethane
- Fluoroplastics
Notes
- ↑ Handbook of a chemist. - 2nd ed., Revised. and additional .. - L.-M .: GNTI Chemical Literature, 1962. - T. 1. - P. 358. - 1072 p.
- ↑ 1 2 3 4 5 6 7 8 9 10 Industrial organofluorine products: ref. Edition / B. N. Maksimov, V. G. Barabanov, I. L. Serushkin et al. - 2nd ed., trans. and additional .. - St. Petersburg. : “Chemistry”, 1996. - 544 p. - ISBN 5-7245-1043-X .
- ↑ 1 2 3 4 Vereshchagina N.S., Golubev A.N., Dedov A.S., Zakharov V. Yu. Russian Chemical Journal. Journal of the Russian Chemical Society. D.I. Mendeleev. - 2000. - T. XLIV, issue 2. - S. 110-114.
- ↑ 1 2 3 Nefedov O.M., Ioffe A.I., Menginov L.G. Chemistry of carbenes. - M .: "Chemistry", 1990. - S. 254. - 304 p. - ISBN 5-7245-0568.
- ↑ 1 2 Loginov B.A. The amazing world of fluoropolymers. - M. , 2008 .-- 128 s.
- ↑ New reference book of chemist and technologist. Radioactive substances. Harmful substances. Hygienic standards / Editorial: Moskvin A.V. et al. - SPb. : ANO NPO Professional, 2004. - 1142 p.