Tetrahydrofuran is an organic compound with the formula4O.
The compound is classified as heterocyclic compound, specifically a cyclic ether.
It is a colorless, water-miscible organic liquid with low viscosity.
THF has an odor similar to acetone.
It is mainly used as a precursor to polymers.
Being polar and having a wide liquid range, THF is a versatile solvent.
Production About two hundred thousand tonnes of tetrahydrofuran
are produced annually.
The most widely used industrial process involves the acid-catalyzed dehydration of 1,4-butanediol.
The method is similar to the production of diethyl ether from ethanol.
The butanediol is derived from condensation of acetylene with formaldehyde followed by
hydrogenation.
Du Pont developed a process for producing THF by oxidizing n-butane to crude maleic
anhydride followed by catalytic hydrogenation.
A third major industrial route entails hydroformylation of allyl alcohol followed by hydrogenation
to the butanediol.
Other methods THF can also be synthesized by catalytic hydrogenation
of furan.
Certain sugars can be converted to THF although this method is not a widely practiced.
Furan is thus derivable from renewable resources.
Applications In the presence of strong acids, THF converts
to a linear polymer called poly(tetramethylene ether) glycol, also known as PTMO, polytetramethylene
oxide: n C4H8O → -(CH2CH2CH2CH2O)n-
This polymer is primarily used to make elastomeric polyurethane fibers like Spandex.
As a solvent The other main application of THF is as an
industrial solvent for PVC and in varnishes.
It is an aprotic solvent with a dielectric constant of 7.6.
It is a moderately polar solvent and can dissolve a wide range of nonpolar and polar chemical
compounds.
THF is water-miscible, and can form solid clathrate hydrate structures with water at
low temperatures.
In the laboratory, THF is a popular solvent when its water miscibility is not an issue.
It is more basic than diethyl ether and forms stronger complexes with Li+, Mg2+, and boranes.
It is a popular solvent for hydroboration reactions and for organometallic compounds
such as organolithium and Grignard reagents.
Although similar to diethyl ether, THF is a stronger base.
Thus, while diethyl ether remains the solvent of choice for some reactions, THF fills that
role in many others where strong coordination is desirable, and the precise properties of
ethereal solvents such as these allows for fine-tuning modern chemical reactions.
Purification Commercial THF contains substantial water
that must be removed for sensitive operations, e.g. those involving organometallic compounds.
Although THF is traditionally dried by distillation from an aggressive desiccant, molecular sieves
are far superior.
Niche uses and research THF has been explored as a water-based co-solvent
to aid in the deconstruction and delignification of plant lignocellulosic biomass, which are
relevant to the production of renewable platform chemicals and sugars.
THF is often used in polymer science.
For example, it can be used to dissolve polymers prior to determining their molecular mass
using gel permeation chromatography.
THF dissolves PVC as well, and thus it is the main ingredient in PVC adhesives.
It can be used to liquefy old PVC cement, and is often used industrially to degrease
metal parts.
THF is used as a component in mobile phases for reversed-phase liquid chromatography.
It has a greater elution strength than methanol or acetonitrile, but is less commonly used
than these solvents.
Other uses THF is also a starting material for the preparation
of tetrahydrothiophene.
In the presence of a solid acid catalyst, it reacts with hydrogen sulfide.
2-MethylTHF 2-Methyltetrahydrofuran has been promoted
as an ecologically friendler alternative to THF.
Whereas 2-MeTHF is more expensive, it may provide for greater overall process economy.
2MeTHF has solvating properties that are intermediate between diethyl ether and THF, has limited
water-miscibility, and forms an azeotrope with water on distillation.
Its lower melting point makes it useful for lower temperature reactions, and its higher
boiling point allows procedures under reflux at higher temperatures.
Precautions THF is considered a relatively nontoxic solvent,
with the median lethal dose comparable to that for acetone.
Reflecting its remarkable solvent properties, it penetrates the skin causing rapid dehydration.
THF readily dissolves latex and is typically handled with nitrile or neoprene rubber gloves.
It is highly flammable.
One danger posed by THF follows from its tendency to form highly-explosive peroxides on storage
in air.
To minimize this problem, commercial samples of THF are often inhibited with BHT.
THF should not be distilled to dryness, because the explosive peroxides concentrate in the
residue.
See also Monomer
Polytetrahydrofuran Trapp mixture
References
General reference Loudon, G. Mark.
Organic Chemistry 4th ed.
New York: Oxford University Press.
2002.
pg 318 External links
International Chemical Safety Card 0578 NIOSH Pocket Guide to Chemical Hazards
THF usage U.S. OSHA info on THF
"2-Methyltetrahydrofuran, An alternative to Tetrahydrofuran and Dichloromethane".
Sigma-Aldrich.
Retrieved 2007-05-23.