Tetrahydrofuran

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Tetrahydrofuran
Tetrahydrofuran bottle and sample.jpg
THF sample and original bottle
Names
IUPAC name
Tetrahydrofuran
Preferred IUPAC name
Oxolane
Other names
1,4-Epoxybutane
Butylene oxide
Cyclotetramethylene oxide
Diethylene oxide
Furanidine
Oxacyclopentane
Tetrahydro-furan
Tetra-methylene oxide
THF
Properties
C4H8O
Molar mass 72.11 g/mol
Appearance Colorless liquid
Odor Ether-like
Density 0.8892 g/cm3 (20 °C)
Melting point −108.4 °C (−163.1 °F; 164.8 K)
Boiling point 66 °C (151 °F; 339 K)
Miscible
Solubility Miscible with acetone, diethyl ether, ethanol
Vapor pressure 132 mmHg (20 °C)
Thermochemistry
Hazards
Safety data sheet Sigma-Aldrich
Flash point −14 °C
Lethal dose or concentration (LD, LC):
1650 mg/kg (rat, oral)
2300 mg/kg (mouse, oral)
2300 mg/kg (guinea pig, oral)
21000 ppm (rat, 3 hr)
Related compounds
Related compounds
Diethyl ether
Furan
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Tetrahydrofuran or simply THF is an organic compound used as a solvent in chemistry. It is a heterocyclic compound, specifically a cyclic ether, or furan, with the formula (CH2)4O.

Properties

Chemical

THF will dissolve most plastics. In the presence of strong acids, THF converts to a linear polymer called poly(tetramethylene ether) glycol (PTMEG), used in the production of Spandex.

n C4H8O → -(CH2CH2CH2CH2O)n-

THF can be produced by acid-catalyzed dehydration of 1,4-butanediol.

THF forms adduct complexes with lithium, magnesium, and boranes.[2]

Physical

Freshly distilled THF.

THF is a clear, colorless, water-miscible polar organic liquid with low viscosity. Its odor is sometimes described as between acetone and diethyl ether. THF has a melting point of −108.4 °C and boils at 66 °C. It has a density of 0.8892 g/cm3 at standard conditions.

Availability

THF is very hard to find, as most chemical suppliers will charge various hazard fees for it. In some countries it's a controlled substance because of its use in synthesizing GHB; for example, in Russia, it's a FSKN List IV chemical.

Certain PVC glues contain a mixture of THF and cyclohexanone. Other PVC glues also have methyl ethyl ketone as a third component. Distillation is required to extract the solvents from the PVC glue, while fractional distillation can be used to purify it.

Preparation

THF is difficult to synthesize by the amateur chemist. Industrially is made via acid-catalyzed dehydration of 1,4-butanediol, though this route is not feasible for the amateur, as the latter is classified as a controlled substance in certain countries and US states.

One method discussed involves the cyclization of n-butanol, via two ways: in benzene at 80°C or irradiated with UV light at room temperature, both in the presence of lead(IV) acetate. The lead(IV) acetate is reduced to lead(II) acetate, so it needs to be replaced as well. Instead of Pb(OAc)4, a mixture of halogen (Br2 or I2) and an oxide or salt of silver or mercury, such as silver acetate or mercury(II) oxide can also be used[3]

Other methods involve catalytic hydrogenation of furan using Raney nickel at 2-4 atm, for three hours, the yield of this route is 93%.[4] Pentose has also been used in hydrogenation processes. Similar methods can also be used to produce the less polar ether 2-methyltetrahydrofuran.

Projects

  • Organometallic syntheses
  • Stabilizing chromium(II) and samarium(II) compounds
  • Organic extractions

Handling

Safety

THF is considered a relatively nontoxic solvent, with the median lethal dose close to that for acetone. However it is a strong irritant and penetrates the skin quickly, causing rapid dehydration. THF readily dissolves latex, so nitrile or neoprene gloves are required for handling the the solvent. It will also attack and soften most plastics.

Storage

Just like the other ethers, THF will form explosive peroxides when stored in air, so must never be distilled to dryness. Butylated hydroxytoluene (BHT) is usually added to limit the peroxide formation. Sodium hydroxide pellets are usually added to precipitate the resulting peroxides.

THF is hygroscopic, so it's recommended to be dried before use. Molecular sieves are good for drying, as well as distillation.

Disposal

THF can be safely burned, although this is not recommended if the solution is very old. THF must never be poured down the drain.

References

  1. Cass et al.; Journal of the Chemical Society; (1958); p. 1406,1407
  2. http://en.wikipedia.org/wiki/Adduct
  3. March's Advanced Organic Chemistry: Reactions, Mechanisms, and Structure; Michael B. Smith, Jerry March, p. 965-966
  4. Tarbell, Weaver; Journal of the American Chemical Society; vol. 63; (1941); p. 2939,2942

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