Tetrahydrofuran
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.
Contents
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.[1]
Physical
THF is a clear, colorless, water-miscible polar organic liquid with low viscosity. Its odor is similar to acetone. 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 it will charge various hazard fees for it.
Certain PVC glues contain a mixture of THF and cyclohexanone. Distillation is required to extract the compound.
Preparation
THF is difficult to synthesize by the amateur chemist. Industrially is made via acid-catalyzed dehydration of 1,4-butanediol, the latter being 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 mercuric oxide can also be used[2]
Other methods involve catalytic hydrogenation of furan or conversion of pentose.
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
- ↑ http://en.wikipedia.org/wiki/Adduct
- ↑ March's Advanced Organic Chemistry: Reactions, Mechanisms, and Structure By Michael B. Smith, Jerry March, p. 965-966
