:Cumene process

Cumene is formed in the gas-phase Friedel–Crafts alkylation of benzene by propene. Benzene and propene are compressed together to a pressure of 30 standard atmospheres at 250 °C in presence of a catalytic Lewis acid. Phosphoric acid is often favored over aluminium halides. Cumene is oxidized in air, which removes the tertiary benzylic hydrogen from cumene and hence forms a cumene radical:

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The cumene radical then bonds with an oxygen molecule to give cumene peroxide radical, which in turn forms cumene hydroperoxide (C₆H₅C(CH₃)₂O₂H) by abstracting a 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.

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Cumene hydroperoxide undergoes a rearrangement reaction in an acidic medium (the Hock rearrangement) to give phenol and acetone. In the first step, the terminal hydroperoxy oxygen atom is protonated. This is followed by a step in which the phenyl group migrates from the benzyl carbon to the adjacent oxygen and a water molecule is lost, producing a resonance stabilized tertiary carbocation. The concerted mechanism of this step is similar to the mechanisms of the Baeyer–Villiger oxidation{{cite book|last=Streitwieser|first=A|author2=Heathcock, C.H.|others=Kosower, E.M.|title=Introduction to Organic Chemistry|publisher=MacMillan|location=New York|year=1992|edition=4th|pages=[https://archive.org/details/introductiontoor00stre_0/page/1018 1018]|chapter=30|isbn=0-02-418170-6|chapter-url=https://archive.org/details/introductiontoor00stre_0/page/1018}} and Criegee rearrangement reactions, and also the oxidation step of the hydroboration–oxidation process.{{cite book|last=K.P.C.|first=Vollhardt|author2=N.E. Schore|authorlink2=Neil E. Schore|title=Organic Chemistry: Structure and Function|publisher=Freeman|location=New York|year=2003|edition=4th|chapter-url=https://archive.org/details/organicchemistry00voll_0/page/988 |page=988|chapter=22|isbn=0-7167-4374-4}}

In 2009, an acidified bentonite clay was proven to be a more economical catalyst than sulfuric acid as the acid medium.

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The resulting carbocation is then attacked by water, forming a hemiacetal-like structure. After transfer of a proton from the hydroxy oxygen to the ether oxygen, the ion falls apart into phenol and acetone.

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Cyclohexylbenzene can replace isopropylbenzene. Via the Hock rearrangement, cyclohexylbenzene hydroperoxide cleaves to give phenol and cyclohexanone. Cyclohexanone is an important precursor to some nylons.{{cite web |url=https://www.acs.org/content/acs/en/pressroom/cutting-edge-chemistry/what-s-new-in-phenol-production-.html |title=What's New in Phenol Production? |last=Plotkin |first=Jeffrey S. |publisher=American Chemical Society |date=2016-03-21 |access-date=2018-01-02 |archive-url=https://web.archive.org/web/20191027122212/https://www.acs.org/content/acs/en/pressroom/cutting-edge-chemistry/what-s-new-in-phenol-production-.html |archive-date=2019-10-27 |url-status=dead }}

Starting with the alkylation of benzene with mixture of 1 and 2-butenes, the cumene process produces phenol and butanones.

• Hydroquinone is prepared by dialkylation of benzene with propene to give 1,4-diisopropylbenzene. This compound reacts with air to afford the bis(hydroperoxide). Analogous to the behavior of cumene hydroperoxide, it rearranges in acid to give acetone and hydroquinone. Oxidation of hydroquinone gives 1,4-benzoquinone:Gerhard Franz, Roger A. Sheldon "Oxidation" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2000 {{doi|10.1002/14356007.a18_261}}
• :C6H4(CHMe2)2 + 2 1/2 O2 -> C6H4O2 + 2 OCMe2 + H2O
• Resorcinol is analogously prepared by converting 1,3-Diisopropylbenzene into the bis(hydroperoxide), which fragments to resorcinol and acetone.{{Ullmann |title=Resorcinol|author1=K. W. Schmiedel |author2=D. Decker |doi=10.1002/14356007.a23_111.pub2|year=2012}}
• 2-Naphthol can also be produced by a method analogous to the cumene process.Gerald Booth "Naphthalene Derivatives" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim. {{doi|10.1002/14356007.a17_009}}.
• 3-Chlorophenol, which does not arise by chlorination of phenol, can be produced by cumene process beginning with the alkylation of chlorobenzene with propylene.{{Ullmann|author1=François Muller |author2=Liliane Caillard |title=Chlorophenols |year=2011 |doi=10.1002/14356007.a07_001.pub2}}
• Cresols are produced from isopropyltoluene.{{cite book |title=Syntheses and Uses of Hydroperoxides and Dialkylperoxides |editor1-first=Saul |editor1-last=Patai |author=Roger A. Sheldon |chapter=Synthesis and uses of alkyl hydroperoxides and dialkyl peroxides |year=1983 |publisher=John Wiley & Sons |doi=10.1002/9780470771730.ch6 |series=PATAI'S Chemistry of Functional Groups|pages=161–200 |isbn=978-0-471-10218-2 }}

Crude acetone is hydrogenated in the liquid phase over Raney nickel or a mixture of copper and chromium oxide to give isopropyl alcohol. This process is useful, when it is coupled with excess acetone production.{{Ullmann |author=Papa, A. J. |title=Propanols |doi=10.1002/14356007.a22_173}}

Mitsui & Co. developed additional step(s) to hydrogenating acetone and dehydrating the isopropanol product to propene, which is recycled as a starting reactant.

Byproducts of the cumene process to produce phenol and acetone are acetophenone and alpha-methylstyrene.

• Bisphenol A
• Dow process (phenol)
• Friedel Crafts alkylation
• Baeyer–Villiger oxidation
• Raschig–Hooker process (also produces phenol)

{{Reflist}}

• [http://www.essentialchemicalindustry.org/chemicals/phenol.html Phenol -- The essential chemical industry online]

{{commons category|Cumene process}}

Category:Chemical processes

Category:Soviet inventions