Tetrahydrofuran

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Tetrahydrofuran
Identifiers
CAS number109-99-9 YesY
PubChem8028
ChemSpider7737 YesY
ChEBICHEBI:26911 N
ChEMBLCHEMBL276521 YesY
RTECS numberLU5950000
Jmol-3D imagesImage 1
Properties
Molecular formulaC4H8O
Molar mass72.11 g mol−1
Appearancecolorless liquid
Density0.8892 g/cm3 @ 20 °C, liquid
Melting point−108.4 °C; −163.1 °F; 164.8 K
Boiling point66 °C; 151 °F; 339 K
Solubility in waterMiscible
Viscosity0.48 cP at 25 °C
Structure
Molecular shapeenvelope
Dipole moment1.63 D (gas)
Hazards
MSDSExternal MSDS
EU classificationFlammable (F)
Irritant (Xi)
R-phrasesR11, R19, R20/21/22, R36/37
S-phrasesS16, S29, S33
NFPA 704
NFPA 704.svg
3
2
1
Flash point−14 °C; 7 °F; 259 K
Related compounds
Related heterocyclesFuran
Pyrrolidine
Dioxane
Related compoundsDiethyl ether
Supplementary data page
Structure and
properties
n, εr, etc.
Thermodynamic
data
Phase behaviour
Solid, liquid, gas
Spectral dataUV, IR, NMR, MS
 N (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references
 
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Tetrahydrofuran
Identifiers
CAS number109-99-9 YesY
PubChem8028
ChemSpider7737 YesY
ChEBICHEBI:26911 N
ChEMBLCHEMBL276521 YesY
RTECS numberLU5950000
Jmol-3D imagesImage 1
Properties
Molecular formulaC4H8O
Molar mass72.11 g mol−1
Appearancecolorless liquid
Density0.8892 g/cm3 @ 20 °C, liquid
Melting point−108.4 °C; −163.1 °F; 164.8 K
Boiling point66 °C; 151 °F; 339 K
Solubility in waterMiscible
Viscosity0.48 cP at 25 °C
Structure
Molecular shapeenvelope
Dipole moment1.63 D (gas)
Hazards
MSDSExternal MSDS
EU classificationFlammable (F)
Irritant (Xi)
R-phrasesR11, R19, R20/21/22, R36/37
S-phrasesS16, S29, S33
NFPA 704
NFPA 704.svg
3
2
1
Flash point−14 °C; 7 °F; 259 K
Related compounds
Related heterocyclesFuran
Pyrrolidine
Dioxane
Related compoundsDiethyl ether
Supplementary data page
Structure and
properties
n, εr, etc.
Thermodynamic
data
Phase behaviour
Solid, liquid, gas
Spectral dataUV, IR, NMR, MS
 N (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Tetrahydrofuran (THF) is an organic compound with the formula (CH2)4O. It is a colorless, water-miscible organic liquid with low viscosity. The compound is classified as heterocyclic compound. THF has an odor similar to acetone. As one of the most polar ethers with a wide liquid range, Also a versatile solvent, THF is mainly used as a precursor to polymers.[1]

Production[edit]

About two hundred thousand tonnes of tetrahydrofuran are produced annually.[2] 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 condensation of acetylene with formaldehyde followed by hydrogenation.[1] Du Pont developed a process for producing THF by oxidizing n-butane to crude maleic anhydride followed by catalytic hydrogenation.[3] 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.[4][5] Where furan is derived from pentose, this method can involve renewable resources. Nevertheless, this route is not widely practiced.

Applications[edit]

In the presence of strong acids, THF converts to a linear polymer called poly(tetramethylene ether) glycol (PTMEG), also known as PTMO, polytetramethylene oxide. This polymer is primarily used to make elastomeric polyurethane fibers like Spandex.[6]

THF is also a starting material for the preparation of tetrahydrothiophene using hydrogen sulfide over a heterogenous acid catalyst.[7]

As a solvent[edit]

The other main application of THF is as an industrial solvent for PVC and in varnishes.[1] 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.[8] THF is water-miscible, and can form solid clathrate hydrate structures with water at low temperatures.[9]

Laboratory use[edit]

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.[10] Although similar to diethyl ether, THF is a stronger base.[11] 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. 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.[12]

Drying of THF
Drying agentDuration of dryingwater content
none0 hours108 ppm
Sodium/benzophenone48 h43 ppm
3 A molecular sieves (20% by volume)72 h4 ppm

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.

2-MethylTHF[edit]

2-Methyltetrahydrofuran (2MeTHF) has been promoted as an ecologically friendler alternative to THF.[13] 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[edit]

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.

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.

Tetrahydrofuran peroxide formation.svg

See also[edit]

References[edit]

  1. ^ a b c Herbert Müller, "Tetrahydrofuran" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. doi:10.1002/14356007.a26_221
  2. ^ "Ethers, by Lawrence Karas and W. J. Piel". Kirk‑Othmer Encyclopedia of Chemical Technology. John Wiley & Sons, Inc. 2004. 
  3. ^ Merck Index of Chemicals and Drugs, 9th ed.
  4. ^ Morrison, Robert Thornton; Boyd, Robert Neilson: Organic Chemistry, 2nd ed., Allyn and Bacon 1972, p. 569
  5. ^ Donald Starr and R. M. Hixon (1943), "Tetrahydrofuran", Org. Synth. ; Coll. Vol. 2: 566 
  6. ^ "Polyethers, Tetrahydrofuran and Oxetane Polymers by Gerfried Pruckmayr, P. Dreyfuss, M. P. Dreyfuss". Kirk‑Othmer Encyclopedia of Chemical Technology. John Wiley & Sons, Inc. 1996. 
  7. ^ Jonathan Swanston “Thiophene” in Ullmann’s Encyclopedia of Industrial Chemistry Wiley-VCH, Weinheim, 2006. doi:10.1002/14356007.a26_793.pub2.
  8. ^ "Chemical Reactivity". Cem.msu.edu. Retrieved 2010-02-15. 
  9. ^ "FileAve.com". Gashydrate.fileave.com. Retrieved 2010-02-15. 
  10. ^ Elschenbroich, C.; Salzer, A. ”Organometallics : A Concise Introduction” (2nd Ed) (1992) Wiley-VCH: Weinheim. ISBN 3-527-28165-7
  11. ^ E.g., B.L. Lucht, D.B. Collum "Lithium Hexamethyldisilazide: A View of Lithium Ion Solvation through a Glass-Bottom Boat" Accounts of Chemical Research, 1999, volume 32, 1035–1042 doi:10.1021/ar960300e, and references therein.
  12. ^ Williams, D. B. G., Lawton, M., "Drying of Organic Solvents: Quantitative Evaluation of the Efficiency of Several Desiccants", The Journal of Organic Chemistry 2010, vol. 75, 8351. doi: 10.1021/jo101589h
  13. ^ "Greener Solvent Alternatives – Brochure" (PDF). Retrieved 2010-02-15. 

General reference[edit]

External links[edit]