THF sample and original bottle
| IUPAC name
| Preferred IUPAC name
| Other names
|Molar mass||72.11 g/mol|
|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)|
|Solubility|| Miscible with acetone, benzene, benzyl alcohol, chloroform, diethyl ether, ethanol, ethylene glycol, methanol, toluene|
Immiscible with glycerol
|Vapor pressure||132 mmHg (20 °C)|
|Safety data sheet||Sigma-Aldrich|
|Flash point||−14 °C|
|Lethal dose or concentration (LD, LC):|
LD50 (Median dose)
| 1,650 mg/kg (rat, oral)|
2,300 mg/kg (mouse, oral)
2,300 mg/kg (guinea pig, oral)
LC50 (Median concentration)
|21,000 ppm (rat, 3 hr)|
| Diethyl ether|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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.
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 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 is lighter than water, with a density of 0.8892 g/cm3 at standard conditions.
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.
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 this compound is classified as a controlled substance in certain countries and US states, being a GBL and GHB precursor.
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
Other methods involve catalytic hydrogenation of furan using Raney nickel at 2-4 atm, for three hours, the yield of this route is 93%. Pentose has also been used in hydrogenation processes. Similar methods can also be used to produce the less polar ether 2-methyltetrahydrofuran.
- Organometallic syntheses
- Stabilizing chromium(II) and samarium(II) compounds
- Organic extractions
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.
THF is highly flammable and will easily catch fire if ignited.
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.
Tetrahydrofuran can be safely burned, as long as it contains no detectable amounts of peroxides. If the THF tests positive for peroxides, but there is no visible precipitate in the ether, it's possible to neutralize the dissolved peroxides. Reducing agents, like ferrous sulfate, sodium bisulfite or metabisulfite added in excess can be used to neutralize the peroxides. After neutralization, the THF should be tested again for peroxides and if none are present, it can be safely burned.
If it's an old bottle, which has visible peroxide in the solution, or if very old, is very likely to have peroxides on the cap, DO NOT OPEN THE BOTTLE! Instead take it to a remote of special area and safely detonate it. The latter may or may not require professional help, depending on the severity of the case.
THF must never be poured down the drain.
- Cass et al.; Journal of the Chemical Society; (1958); p. 1406,1407
- March's Advanced Organic Chemistry: Reactions, Mechanisms, and Structure; Michael B. Smith, Jerry March, p. 965-966
- Tarbell, Weaver; Journal of the American Chemical Society; vol. 63; (1941); p. 2939,2942