Tetrahydrofuran


 * For other uses of THF, see THF (disambiguation)

Tetrahydrofuran is a heterocyclic organic compound. It is a clear, low-viscosity liquid with a diethyl ether-like smell. It is one of the most polar ethers and is used as a solvent of intermediate polarity in chemical reactions. THF is an aprotic, electron donating solvent with a dielectric constant of 7.6. THF is the fully hydrogenated analog of the aromatic compound furan.

Uses
THF is a moderately polar, aprotic solvent. It is able to dissolve a wide range of compounds.

Diethyl ether can often be substituted with THF, especially when a higher-boiling solvent is required. Thus THF, like diethyl ether, is often used for hydroborations used to synthesize primary alcohols. Both ethers have an oxygen atom which can coordinate to the electron-deficient boron atom, forming an adduct. Similarly, THF or diethyl ether are often used as solvents for Grignard reagents because of the oxygen atom's ability to coordinate to the magnesium atom on the Grignard reagent. In addition, the oxygen atom has no acid hydrogen that can undergo acid-base reaction with the Grignard reagent. 2-methyltetrahydrofuran has become a popular THF alternative, based on its similar properties to THF, but having a lower melting point (useful for lower temperature reactions), as well as having a higher boiling point (useful for solvent retention under reflux).

THF is often used in polymer science. For example, it can be used to dissolve rubber prior to determining its molecular mass using gel permeation chromatography.

THF can be polymerized by strong acids to give a linear polymer called poly(tetramethylene ether) glycol (PTMEG),(CAS Registry Number, [25190-06-1], also known as PTMO, polytetramethylene oxide. The primary use of this polymer is to make elastomeric polyurethane fibers like Spandex..

It is often used industrially to degrease metal parts.

Preparation
THF can be synthesized by catalytic hydrogenation of furan.

The major industrial process for making THF is the acid-catalyzed dehydration of 1,4-butanediol. . Du Pont developed a process for producing THF by oxidizing n-butane to crude maleic anhydride, followed by catalytic hydrogenation of maleic anhydride to THF.

Precautions
THF tends to form peroxides on storage. As a result, THF should not be distilled to dryness, which can leave a residue of highly-explosive peroxides. Commercial THF is therefore often inhibited with BHT.