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.[3]

Synthesis

Isoprenol is produced by the reaction between isobutene (2-methylpropene) and formaldehyde, in what is arguably the simplest example of the Prins reaction.

The reaction of isobutene with formaldehyde to give isoprenol, the first step in the industrial manufacture of prenol.
The reaction of isobutene with formaldehyde to give isoprenol, the first step in the industrial manufacture of prenol.

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:

The isomerization of isoprenol to prenol, the second step in the industrial manufacture of prenol.
The isomerization of isoprenol to prenol, the second step in the industrial manufacture of prenol.

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.[4]

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 at scale using a silica-supported silver catalyst.[5]

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.[6] Isoprenol is also used in the synthesis of some pyrethroid pesticides.

Notes

  1. ^ 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.

References

  1. ^ Sigma-Aldrich Co., 3-Methyl-3-buten-1-ol. Retrieved on 2009-08-31..
  2. ^ HSNO Chemical Classification Information Database, New Zealand Environmental Risk Management Authority, retrieved 2009-08-31.
  3. ^ 3-Methyl-2-buten-1-ol (PDF), SIDS Initial Assessment Report, Geneva: United Nations Environment Programme, May 2005. Major produce in a world is BASF(Germany) and Kuraray(Japan).
  4. ^ Kogan, S; Kaliya, M; Froumin, N (6 January 2006). "Liquid phase isomerization of isoprenol into prenol in hydrogen environment". Applied Catalysis A: General. 297 (2): 231–236. doi:10.1016/j.apcata.2005.09.010.
  5. ^ Hoelderich, Wolfgang F.; Kollmer, Felix (1 January 2000). "Oxidation reactions in the synthesis of fine and intermediate chemicals using environmentally benign oxidants and the right reactor system". Pure and Applied Chemistry. 72 (7): 1273–1287. doi:10.1351/pac200072071273.
  6. ^ Bonrath, Werner; Gao, Bo; Houston, Peter; McClymont, Tom; Müller, Marc-André; Schäfer, Christian; Schweiggert, Christiane; Schütz, Jan; Medlock, Jonathan A. (15 September 2023). "75 Years of Vitamin A Production: A Historical and Scientific Overview of the Development of New Methodologies in Chemistry, Formulation, and Biotechnology". Organic Process Research & Development. 27 (9): 1557–1584. doi:10.1021/acs.oprd.3c00161.
Allikas: https://en.wikipedia.org/wiki/Isoprenol
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