Tetrahydrofuran ( THF), or oxolane, is an organic compound with the formula (CH2)4O. The compound is classified as heterocyclic compound, specifically a cyclic ether. It is a colorless, water-miscible organic liquid with low viscosity. It is mainly used as a precursor to polymers.[ Being polar molecule and having a wide liquid range, THF is a versatile solvent. It is an isomer of another solvent, butanone.
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Production
About 200,000 of tetrahydrofuran are produced annually.[ DuPont developed a process for producing THF by oxidizing n-butane to crude maleic anhydride, followed by catalytic hydrogenation.]
Other methods
THF can also be synthesized by catalytic hydrogenation of furan.
Applications
Polymerization
In the presence of , THF converts to a linear polymer called poly(tetramethylene ether) glycol (PTMEG), also known as polytetramethylene oxide (PTMO):
n \, \ce{C4H8O} \quad \xrightarrow{\text{strong}{} \quad \bigl\!\!\!_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 polyvinyl chloride (PVC) and in .
THF has been explored as a miscible co-solvent in aqueous solution to aid in the liquefaction and delignification of plant lignocellulosic biomass for production of renewable platform chemicals and sugars as potential precursors to biofuels.
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.
THF is used as a solvent in 3D printing when printing with PLA, PETG and substantially similar filaments. It can be used to clean clogged 3D printer parts, to remove extruder lines and add a shine to the finished product as well as to solvent welding printed parts.
Laboratory use
In the laboratory, THF is a popular solvent when its water miscibility is not an issue. It is more basic than diethyl ether
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 such as elemental sodium, have been shown to be superior water scavengers.
Reaction with hydrogen sulfide
In the presence of a solid acid catalyst, THF reacts with hydrogen sulfide to give tetrahydrothiophene.
Lewis basicity
THF is a Lewis base that bonds to a variety of Lewis acids such as iodine, phenols, triethylaluminum and bis(hexafluoroacetylacetonato)copper(II). THF has been classified in the ECW model and it has been shown that there is no one order of base strengths.[Manzer, L. E. "Tetrahydrofuran Complexes of Selected Early Transition Metals," Inorganic Synthesis. 21, 135–140, (1982).]
Precautions
THF is a relatively acutely nontoxic solvent, with the median lethal dose (LD50) comparable to that for acetone. However, chronic exposure is suspected of causing cancer.
One danger posed by THF is its tendency to form the explosive compound organic peroxide upon reaction with air:
To minimize this problem, commercial supplies of THF are often stabilized with butylated hydroxytoluene (BHT). Distillation of THF to dryness is unsafe because the explosive peroxides can concentrate in the residue.
Related compounds
Tetrahydrofurans
The tetrahydrofuran ring is found in diverse natural products including , , and polyketide natural products.
Oxolanes
Tetrahydrofuran is one of the class of pentic cyclic ethers called oxolanes. There are seven possible structures, namely,
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Monoxolane, the root of the group, synonymous with tetrahydrofuran
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1,3-dioxolane
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1,2-dioxolane
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1,2,4-trioxolane
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1,2,3-trioxolane
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tetroxolane
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pentoxolane
See also
General reference
External links
