| Tetrahydrofuran | |
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Oxolane |
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Other names
THF, tetrahydrofuran, 1,4-epoxybutane, butylene oxide, cyclotetramethylene oxide, oxacyclopentane, diethylene oxide, furanidine, hydrofuran, tetra-methylene oxide |
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| Identifiers | |
| CAS number | 109-99-9 |
| PubChem | 8028 |
| ChemSpider | 7737 |
| ChEBI | CHEBI:26911 |
| ChEMBL | CHEMBL276521 |
| RTECS number | LU5950000 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | C4H8O |
| Molar mass | 72.11 g mol−1 |
| Appearance | colorless liquid |
| Density | 0.8892 g/cm3 @ 20 °C, liquid |
| Melting point |
−108.4 °C, 165 K, -163 °F |
| Boiling point |
66 °C, 339 K, 151 °F |
| Solubility in water | Miscible |
| Viscosity | 0.48 cP at 25 °C |
| Structure | |
| Molecular shape | envelope |
| Dipole moment | 1.63 D (gas) |
| Hazards | |
| MSDS | External MSDS |
| EU classification | Flammable (F) Irritant (Xi) |
| R-phrases | R11, R19, R36/37 |
| S-phrases | S16, S29, S33 |
| NFPA 704 |
3
2
0
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| Flash point | −14 °C |
| Related compounds | |
| Related heterocycles | Furan Pyrrolidine Dioxane |
| Related compounds | Diethyl ether |
| Supplementary data page | |
| Structure and properties |
n, εr, etc. |
| Thermodynamic data |
Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Tetrahydrofuran (THF) is a colorless, water-miscible organic liquid with low viscosity at standard temperature and pressure. This heterocyclic compound has the chemical formula (CH2)4O. As one of the most polar ethers with a wide liquid range, it is a useful solvent. Its main use, however, is as a precursor to polymers. THF has an odor similar to its chemical cousin, diethyl ether, but is a much less potent anesthetic than diethyl ether.
Contents |
About two hundred thousand tonnes of tetrahydrofuran are produced annually.[1] The most widely used industrial process involves the acid-catalyzed dehydration of 1,4-butanediol, akin to the production of diethyl ether from ethanol. The butanediol is derived from carbonylation of acetylene followed by hydrogenation. Du Pont developed a process for producing THF by oxidizing n-butane to crude maleic anhydride followed by catalytic hydrogenation.[2] A third major industrial route entails hydroformylation of allyl alcohol followed by hydrogenation to the butanediol.
THF can also be synthesized by catalytic hydrogenation of furan.[3][4] Where furan is derived from pentose, this method can involve renewable resources. Nevertheless, this route is not widely practiced.
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.[5]
The other main application of THF is as an industrial solvent for PVC and in varnishes.[6] 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.[7] THF is water-miscible, and can form solid clathrate hydrate structures with water at low temperatures.[8]
Although a minor application, THF is a popular solvent in the laboratory when a moderately higher-boiling ethereal solvent is required and its water miscibility is not an issue. The oxygen center of ethers can coordinate to Lewis acids such as Li+, Mg2+, and boranes, forming adducts. Hence, like diethyl ether, THF can be used in hydroboration reactions to synthesize primary alcohols, and as a solvent for organometallic compounds such as organolithium and Grignard reagents.[9] Although similar to diethyl ether, THF is a stronger base.[10] 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 for fine-tuning modern chemical reactions.
THF is often used in polymer science. For example, it can be used to dissolve polymers prior to determining its molecular mass using gel permeation chromatography. THF dissolves PVC as well and 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.
2-Methyltetrahydrofuran (2MeTHF) is a THF alternative that is being promoted as being more ecologically friendly.[11] 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).
THF is considered a relatively nontoxic solvent, with the median lethal dose (LD50) 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.
The greatest 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.