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]

Isoprenol is produced by the reaction between isobutene (2-methylpropene) and formaldehyde.

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.

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]

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. ^ See, e.g., Kogan, S. B.; Kaliya, M.; Froumin, N. (2006), "Liquid phase isomerization of isoprenol into prenol in hydrogen environment", Appl. Catal. A: Gen., 297 (2): 231–36, doi:10.1016/j.apcata.2005.09.010.