isoprenol
{{chembox
| Watchedfields = changed
| verifiedrevid = 464369911
| Name = Isoprenol
| ImageFile = Structural formula of isoprenol.svg
| ImageSize = 200px
| ImageName = Structural formula of isoprenol
| ImageFile1 = Isoprenol-3D-balls.png
| ImageSize1 = 180px
| ImageName1 = Ball-and-stick model of prenol
| PIN = 3-Methylbut-3-en-1-ol
| OtherNames = 3-Methyl-3-buten-1-ol
|Section1={{Chembox Identifiers
| InChI = 1/C5H10O/c1-5(2)3-4-6/h6H,1,3-4H2,2H3
| SMILES = OCCC(=C)C
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/C5H10O/c1-5(2)3-4-6/h6H,1,3-4H2,2H3
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = CPJRRXSHAYUTGL-UHFFFAOYSA-N
| CASNo = 763-32-6
| CASNo_Ref = {{cascite|correct|CAS}}
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 12448
| PubChem = 12988
| ChEBI = 62898
| EC_number = 212-110-8
| UNII = KJ25C8CPFA
| ChEMBL = 3561140
}}
|Section2={{Chembox Properties
| Properties_ref = {{Aldrich|id=W519308|name=3-Methyl-3-buten-1-ol|accessdate=2009-08-31}}.
| Formula = C5H10O
| MolarMass = 86.132 g/mol
| BoilingPtC = 130 to 132
| BoilingPt_notes =
| Density = 0.853 g/cm3
| RefractIndex = 1.433
}}
|Section7={{Chembox Hazards
| Hazards_ref = {{GHS class NZ|id=13375|access-date = 2009-08-31}}.
| GHSPictograms = {{GHS flame|Flam. Liq. 3}}{{GHS exclamation mark|Eye Irrit. 2}}
| GHSSignalWord = WARNING
| HPhrases = {{H-phrases|226|319}}
| PPhrases = {{P-phrases|210|233|240|241|242|243|264|280|303+361+353|305+351+338|337+313|370+378|403+235|501}}
| FlashPtC = 36
| FlashPt_ref = Sigma-Aldrich Co. gives a value for the flash point of isoprenol of 42 °C (108 °F). The difference in the two values does not alter the safety classification of isoprenol as a category 3 flammable liquid under the GHS; but the lower value quoted here (from the New Zealand Environmental Risk Management Authority) would make it a class IC flammable liquid instead of a class II combustible liquid under the U.S. OSHA classification (29 C.F.R § 1910.106), and F3 rather than F2 under the NFPA 704 standard.
}}
|Section8={{Chembox Related
| OtherCompounds = Prenol
}}
}}
Isoprenol, also known as 3-methylbut-3-en-1-ol, is a hemiterpene alcohol. It is produced industrially as an intermediate to 3-methylbut-2-en-1-ol (prenol): global production in 2001 can be estimated as 6–13 thousand tons.{{SIDS-ref|id=556821|name=3-Methyl-2-buten-1-ol|date=May 2005}}. Major produce in a world is BASF(Germany) and Kuraray(Japan).
Synthesis
Isoprenol is produced by the reaction between isobutene (2-methylpropene) and formaldehyde, in what is arguably the simplest example of the Prins reaction.
:File:Isoprenol prepn.png{{clear|left}}
Reactions
The thermodynamically preferred prenol, with the more substituted double bond, cannot be directly formed in the above reaction but is produced via a subsequent isomerisation:
:File:Prenol prepn.png{{clear|left}}
This isomerisation reaction is catalyzed by any species which can form an allyl complex without excessive hydrogenation of the substrate, for example poisoned palladium catalysts.{{cite journal |last1=Kogan |first1=S |last2=Kaliya |first2=M |last3=Froumin |first3=N |title=Liquid phase isomerization of isoprenol into prenol in hydrogen environment |journal=Applied Catalysis A: General |date=6 January 2006 |volume=297 |issue=2 |pages=231–236 |doi=10.1016/j.apcata.2005.09.010}}
Oxidation (or more technically dehydrogenation) gives the aldehyde (3-methyl-3-butenal), which is used for the industrial synthesis of citral and other compounds. BASF achieves this transformation at scale using a silica-supported silver catalyst.{{cite journal |last1=Hoelderich |first1=Wolfgang F. |last2=Kollmer |first2=Felix |title=Oxidation reactions in the synthesis of fine and intermediate chemicals using environmentally benign oxidants and the right reactor system |journal=Pure and Applied Chemistry |date=1 January 2000 |volume=72 |issue=7 |pages=1273–1287 |doi=10.1351/pac200072071273}}
:File:3-Methyl-3-butenal.svg{{clear|left}}
Uses
Isoprenol is primarily a feedstock used in the production of other more valuable chemicals. Its prenol and 3-methyl-3-butenal derivatives are used together in the formation of citral, which is used both as an aroma compound and as a starting material in the production of ionones such as vitamin E and vitamin A.{{cite journal |last1=Bonrath |first1=Werner |last2=Gao |first2=Bo |last3=Houston |first3=Peter |last4=McClymont |first4=Tom |last5=Müller |first5=Marc-André |last6=Schäfer |first6=Christian |last7=Schweiggert |first7=Christiane |last8=Schütz |first8=Jan |last9=Medlock |first9=Jonathan A. |title=75 Years of Vitamin A Production: A Historical and Scientific Overview of the Development of New Methodologies in Chemistry, Formulation, and Biotechnology |journal=Organic Process Research & Development |date=15 September 2023 |volume=27 |issue=9 |pages=1557–1584 |doi=10.1021/acs.oprd.3c00161|doi-access=free }} Isoprenol is also used in the synthesis of some pyrethroid pesticides.
Notes
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