Tetrahydrofuran

"THF" redirects here. For other uses, see THF (disambiguation).

Tetrahydrofuran

Names
IUPAC name Oxolane
Other names THF, tetrahydrofuran, 1,4-epoxybutane, butylene oxide, cyclotetramethylene oxide, oxacyclopentane, diethylene oxide, furanidine, hydrofuran, tetra-methylene oxide
Identifiers
CAS Number	109-99-9 Y
ChEBI	CHEBI:26911 N
ChEMBL	ChEMBL276521 Y
ChemSpider	7737 Y
Jmol 3D model	Interactive image
PubChem	8028
RTECS number	LU5950000
InChI InChI=1S/C4H8O/c1-2-4-5-3-1/h1-4H2 Y Key: WYURNTSHIVDZCO-UHFFFAOYSA-N Y InChI=1/C4H8O/c1-2-4-5-3-1/h1-4H2 Key: WYURNTSHIVDZCO-UHFFFAOYAI
SMILES C1CCOC1
Properties
Chemical formula	C4H8O
Molar mass	72.11 g·mol−1
Appearance	colorless liquid
Odor	ether-like
Density	0.8892 g/cm3 @ 20 °C, liquid
Melting point	−108.4 °C (−163.1 °F; 164.8 K)
Boiling point	66 °C (151 °F; 339 K)
Solubility in water	Miscible
Vapor pressure	132 mmHg (20°C)
Viscosity	0.48 cP at 25 °C
Structure
Molecular shape	envelope
Dipole moment	1.63 D (gas)
Vapor pressure	{{{value}}}
Related compounds
Related heterocycles	Furan Pyrrolidine Dioxane
Related compounds	Diethyl ether
Supplementary data page
Structure and properties	Refractive index (n), Dielectric constant (εr), etc.
Thermodynamic data	Phase behaviour solid–liquid–gas
Spectral data	UV, IR, NMR, MS
N verify (what is YN ?)
Infobox references

Tetrahydrofuran (THF) 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 and having a wide liquid range, THF is a versatile solvent.

Production

About 200000 t 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 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 (PTMEG), 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 (e.g., Grignard reactions), THF fills that role in many others, where strong coordination is desirable and the precise properties of ethereal solvents such as these (alone and in mixtures and at various temperatures) allows 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.

Drying of THF

Drying agent	Duration of drying	Water content
None	0 hours	108 ppm
Sodium/benzophenone	48 h	43 ppm
3 A molecular sieves (20% by volume)	72 h	4 ppm

Potential uses and research

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. Aqueous THF augments the hydrolysis of glycans from biomass and dissolves the majority of biomass lignin making it a suitable solvent for biomass pretreatment.

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 (2MeTHF) 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 (relative to THF).

Precautions

THF is considered a relatively nontoxic solvent, with the median lethal dose (LD₅₀) comparable to that for acetone. However, it is suspected to cause cancer. 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

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