Cumene

Cumene

Cumene

Chemical compound

Not to be confused with cumin or cumulene.

Cumene (isopropylbenzene) is an organic compound that contains a benzene ring with an isopropyl substituent. It is a constituent of crude oil and refined fuels. It is a flammable colorless liquid that has a boiling point of 152 °C. Nearly all the cumene that is produced as a pure compound on an industrial scale is converted to cumene hydroperoxide, which is an intermediate in the synthesis of other industrially important chemicals, primarily phenol and acetone (known as the cumene process).

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Production

Commercial production of cumene is by Friedel–Crafts alkylation of benzene with propylene. The original route for manufacturing of cumene was by alkylation of benzene in the liquid phase using sulfuric acid as a catalyst, but because of the complicated neutralization and recycling steps required, together with corrosion problems, this process has been largely replaced. As an alternative, solid phosphoric acid (SPA) supported on alumina was used as the catalyst.

Reaction of benzene with propene to cumene in the presence of phosphoric acid supported on silica & promoted with boron trifluoride

Since the mid-1990s, commercial production has switched to zeolite-based catalysts. In this process, the efficiency of cumene production is generally 70-75%. The remaining components are primarily polyisopropyl benzenes. In 1976, an improved cumene process that uses aluminum chloride as a catalyst was developed. The overall conversion of cumene for this process can be as high as 90%.

The addition of two equivalents of propylene gives diisopropylbenzene (DIPB). Using transalkylation, DIPB is comproportionated with benzene to give cumene.[5]

Autoxidation

Depending on the conditions, autoxidation of cumene gives dicumyl peroxide or cumene hydroperoxide. Both reactions exploit the weakness of the tertiary C-H bond. The tendency of cumene to form peroxides by autoxidation poses safety concerns.[6] Tests for peroxides are routinely conducted before heating or distilling.

Applications

Cumene is frequently found as an ingredient in thread locking fluids.[7][8]

See also

References

  1. [1]
    Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. pp. 139, 597. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4.
  2. [2]
    Physical and Thermodynamic Properties of Pure Chemicals Data Compilation. Washington, D.C.: Taylor and Francis. 1989.
  3. [3]
    "Cumene". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  4. [4]
    NIOSH Pocket Guide to Chemical Hazards. "#0159". National Institute for Occupational Safety and Health (NIOSH).
  5. [5]
    Bipin V. Vora; Joseph A. Kocal; Paul T. Barger; Robert J. Schmidt; James A. Johnson (2003). "Alkylation". Kirk-Othmer Encyclopedia of Chemical Technology. Kirk‐Othmer Encyclopedia of Chemical Technology. doi:10.1002/0471238961.0112112508011313.a01.pub2. ISBN 0471238961.
  6. [6]
    CDC - NIOSH Pocket Guide to Chemical Hazards
  7. [7]
    "LOCTITE 242 MS TL Safety Data Sheet".
  8. [8]
    "Wurth Blue Thread Locker Safety Data Sheet" (PDF).
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