Cumene process
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220973775
2008-06-22T13:47:50Z
Edgar181
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Reverted edits by [[Special:Contributions/78.151.99.226|78.151.99.226]] ([[User talk:78.151.99.226|talk]]) to last version by Element16
'''Cumene process''' is an [[industrial process]] for developing [[phenol]] and [[acetone]] from [[benzene]] and [[propylene]]. The term stems from [[cumene]] (isopropyl benzene), the intermediate material during the process.
This process converts two relatively cheap starting materials, [[benzene]] and [[propylene]], into two more valuable ones, phenol and acetone. Other reactants required are [[oxygen]] from air and small amounts of a [[radical initiator]]. Most of the worldwide production of phenol and acetone is now based on this method.
The overall chemical process is summarised below.
[[Image:Cumene-process-overview-2D-skeletal.png|500px|center|Overview of the cumene process]]
==Technical description==
Benzene and propylene are compressed together to a pressure of 30 [[Atmospheric pressure|standard atmospheres]] at 250 °[[Celsius|C]] (482° [[Fahrenheit|F]]) in presence of a [[catalyst|catalytic]] [[Lewis acid]]. [[Phosphoric acid]] is often favored over [[aluminium]] [[halide]]s. Cumene is formed in the gas-phase [[Friedel-Crafts reaction#Friedel-Crafts alkylation|Friedel-Crafts alkylation]] of benzene by propylene:
[[Image:Cumene-formation-2D-skeletal.png|400px|center]]
Cumene is oxidized in slightly [[Base (chemistry)|basic]] conditions in presence of a [[radical initiator]], which removes the tertiary [[benzylic hydrogen]] from cumene and hence forms a cumene [[radical (chemistry)|radical]]:
[[Image:Cumene-radical-formation-2D-skeletal.png|300px|center]]
This cumene radical then [[chemical bond|bonds]] with an oxygen molecule to give cumene [[hydroperoxide]] radical, which in turn forms cumene hydroperoxide (C<sub>6</sub>H<sub>5</sub>C(CH<sub>3</sub>)<sub>2</sub>-O-O-H) by abstracting benzylic hydrogen from another cumene molecule. This latter cumene converts into cumene radical and feeds back into subsequent chain formations of cumene hydroperoxides. A pressure of 5 atm is used to ensure that the unstable peroxide is kept in liquid state.
[[Image:Cumene-peroxide-radical-formation-2D-skeletal.png|400px|center]]
[[Image:Cumene-hydroperoxide-formation-2D-skeletal.png|400px|center]]
Cumene hydroperoxide is then [[Hydrolysis|hydrolysed]] in an [[acid]]ic medium to give [[phenol]] and [[acetone]]. Loss of a water molecule from the hydroperoxide leaves an [[electron deficiency|electron-deficient]] oxygen. Migration of the phenyl to the oxygen leads to a more stable [[resonance (chemistry)|resonance hybridized structure]] of tertiary benzylic radical, which in turn produce acetone and phenol after an attachment of a water molecule and rearrangement. Research suggests the loss of water molecule and phenyl migration may take place simultaneously, in other words the step of the mechanism is concerted{{Fact|date=February 2007}}.
[[Image:Cumene-process-phenyl-migration-2D-skeletal.png|400px|center]]
[[Image:Cumene-process-final-steps-2D-skeletal.png|600px|center]]
The products are extracted by [[distillation]].
==See also==
* [[Chemical synthesis]]
* [[Dow process]]
* [[Friedel Crafts alkylation]]
* [[Baeyer-Villiger oxidation]]
* [[Concerted reaction]]
* [[Raschig process]] (also produces phenol)
==External links==
* [http://www.npi.gov.au/database/substance-info/profiles/28.html National Pollutant Inventory - Cumene fact sheet]
{{commonscat|Cumene process}}
<!-- Categories -->
[[Category:Organic reactions]]
[[Category:Chemical processes]]
[[Category:Industrial processes]]
[[Category:Unit processes]]
[[de:Cumolhydroperoxid-Verfahren]]
[[ja:クメン法]]
[[no:Kumenprosessen]]
[[pl:Metoda kumenowa]]
[[zh:異丙苯法]]