Tetrafluoroethylene

Key takeaways

Tetrafluoroethylene belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Tetrafluoroethylene to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Tetrafluoroethylene from memory before moving on to harder problems.

Reference excerpt

Tetrafluoroethylene (TFE) is a fluorocarbon with the chemical formula C2F4. It is a colorless gas. Its structure is F2C=CF2. It is used primarily in the industrial preparation of fluoropolymers. It is the simplest perfluorinated alkene.

History Tetrafluoroethylene was first obtained by the French chemist [fr] Camille Chabrié by heating tetrachloroethylene with silver(II) fluoride. It was named "dicarbon tetrafluoride" based on its composition, analogous to "dicarbon tetrachloride" for tetrachloroethylene which it was first made from.

Properties Tetrafluoroethylene is a synthetic colorless, odorless gas that is insoluble in water. Like all unsaturated fluorocarbons, it is susceptible to nucleophilic attack. It is unstable towards decomposition to carbon and carbon tetrafluoride (CF4) and prone to form explosive peroxides in contact with air.

Industrial use

Polymerization of tetrafluoroethylene produces fluoropolymers such as Teflon and Fluon. PTFE is one of the two fluorocarbon resins composed wholly of fluorine and carbon. The other resin composed purely of carbon and fluorine is the copolymer of TFE with typically 6–9% hexafluoropropene (HFP), which is known as FEP (fluorinated ethylene propylene copolymer). TFE is also used in the preparation of numerous copolymers that also include hydrogen and/or oxygen, including both fluoroplastics and fluoroelastomers. Typical TFE-based fluoroplastics include ETFE, the alternating 1:1 copolymer with ethylene, and PFA, which is a random copolymer similar to FEP but with a minor amount of a perfluoroalkyl vinyl ether (PAVE) rather than HFP. DuPont uses primarily perfluoro(methylvinylether), whereas Daikin uses primarily perfluoro(propylvinylether) in manufacturing PFA. There are numerous other fluoropolymers that contain tetrafluoroethylene, but usually not at greater than 50% by weight.

Manufacture TFE is manufactured from chloroform. Chloroform is fluorinated by reaction with hydrogen fluoride to produce chlorodifluoromethane (R-22). Pyrolysis of chlorodifluoromethane (at 550–750 °C) yields TFE, with difluorocarbene as an intermediate.

CHCl3 + 2 HF → CHClF2 + 2 HCl 2 CHClF2 → C2F4 + 2 HCl Alternatively, it can be prepared by pyrolysis of fluoroform, which is also produced from chloroform and HF:

2 CHF3 → C2F4 + 2 HF

Laboratory methods A convenient, safe method for generating TFE is the pyrolysis of the sodium salt of pentafluoropropionic acid:

CF3CF2CO−2Na+ → C2F4 + CO2 + NaF The depolymerization reaction – vacuum pyrolysis of PTFE at 650–700 °C (1,200–1,290 °F) in a quartz vessel – is a traditional laboratory synthesis of TFE. The process is however challenging because attention must be paid to pressure, as well as the avoidance of perfluoroisobutene. PTFE polymer cracks, and at a pressure below 5 Torr (670 Pa) exclusively C2F4 is obtained. At higher pressures the product mixture contains hexafluoropropylene and octafluorocyclobutane.

Reactions Tetrafluoroethylene is a reactive molecule that participates in myriad reactions. Owing to the presence of four fluorine substituents, its reactions differ strongly from the behavior of conventional alkenes such as ethylene. Tetrafluoroethylene dimerizes, giving octafluorocyclobutane. Even normal alkenes and dienes add tetrafluoroethylene in a [2+2] manner. 1,3-Butadiene gives 3-vinyl-1,1,2,2-tetrafluorocyclobutane.

Safety The main hazard associated with TFE is that of explosion, especially if oxygen is present. TFE reacts with oxygen at low temperatures to form an explosive oxide, the detonation of which is usually sufficient to trigger explosive decomposition of TFE to C and CF4. Explosions can also be caused by adiabatic compression if the TFE is handled under high pressure, which it typically is in an industrial setting. If pressurised TFE is allowed into a vessel or pipework at a lower pressure, then the atmosphere in the vessel will be compressed by the TFE, causing it to heat up, potentially to the point where it might detonate the TFE. This has been known to cause explosions. In industry, pipework is flushed with pressurized nitrogen, before the introduction of TFE, both to exclude oxygen and prevent adiabatic compression. TFE is an alkylating agent, albeit a weak one, and as such is expected to be a carcinogen. LD50(rat, inhalation) = 40000 ppm. The International Agency for Research on Cancer classifies TFE as probably carcinogenic to humans based on animal studies. TFE is not considered to be a PFAS

See also Tetrachloroethylene 1,1,1,2-Tetrafluoroethane Fluorochemical industry

References

External links National Toxicology Program Chemical Repository Tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride terpolymer – aka THV, melt-processable members of the fluorocarbon family Sleeuwenhoek, Anne; Cherrie, John (2012). "Exposure assessment of tetrafluoroethylene and ammonium perfluorooctanoate 1951–2002". Journal of Environmental Monitoring. 14 (3): 775–781. doi:10.1039/c2em10930a. PMID 22322341.

Illustrations

Worked examples

Example 1 — a first encounter with Tetrafluoroethylene

Start with the simplest possible case. Write down what Tetrafluoroethylene claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Tetrafluoroethylene before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Tetrafluoroethylene ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Tetrafluoroethylene

In research: Tetrafluoroethylene appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Tetrafluoroethylene in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Tetrafluoroethylene is common in secondary-school and first-year university syllabi. It links to neighbouring topics Haloethenes, IARC Group 2A carcinogens, Monomers, so understanding it makes those chapters shorter.
In everyday life: Look for Tetrafluoroethylene outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Tetrafluoroethylene in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Tetrafluoroethylene means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Tetrafluoroethylene out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Tetrafluoroethylene in simple terms?

Tetrafluoroethylene (TFE) is a fluorocarbon with the chemical formula C2F4. It is a colorless gas.

Why does Tetrafluoroethylene matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Tetrafluoroethylene?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Tetrafluoroethylene.