Isoamyl alcohol is a colorless liquid with the formula C
5H
12O, specifically (H3C–)2CH–CH2–CH2–OH. It is one of several isomers of amyl alcohol (pentanol). It is also known as isopentyl alcohol, isopentanol, or (in the IUPAC recommended nomenclature) 3-methyl-butan-1-ol. An obsolete name for it was isobutyl carbinol.[5]

Isoamyl alcohol is an ingredient in the production of banana oil, an ester found in nature and also produced as a flavouring in industry. It is a common fusel alcohol, produced as a major by-product of ethanol fermentation.

Occurrence

Isoamyl alcohol is one of the components of the aroma of Tuber melanosporum, the black truffle.

Fusel alcohols like isoamyl alcohol are grain fermentation byproducts, and therefore trace amounts of isoamyl are present in many alcoholic beverages.

The compound has also been identified as a chemical in the pheromone used by hornets to attract other members of the hive to attack.[6]

Extraction from fusel oil

Isoamyl alcohol can be separated from fusel oil by either of two methods: shaking with strong brine solution and separating the oily layer from the brine layer; distilling it and collecting the fraction that boils between 125 and 140 °C. Further purification is possible with this procedure: shaking the product with hot limewater, separating the oily layer, drying the product with calcium chloride, and distilling it, collecting the fraction boiling between 128 and 132 °C.[5]

Synthesis

Isoamyl alcohol can be synthesized by condensation of isobutene and formaldehyde which produces isoprenol, then hydrogenation. It is a colourless liquid of density 0.8247 g/cm3 (0 °C), boiling at 131.6 °C, slightly soluble in water, and easily dissolved in organic solvents. It has a characteristic strong smell and a sharp burning taste. On passing the vapour through a red-hot tube, it decomposes into acetylene, ethylene, propylene, and other compounds. It is oxidized by chromic acid to isovaleraldehyde, and it forms addition compounds crystals with calcium chloride and tin(IV) chloride.[5]

Uses

Besides its use in the synthesis of banana oil, isoamyl alcohol is also an ingredient of Kovac's reagent, used for the bacterial diagnostic indole test.

It is also used as an antifoaming agent in the chloroform isoamyl alcohol reagent.[7]

Isoamyl alcohol is used in a phenol–chloroform extraction mixed with the chloroform to further inhibit RNase activity and prevent solubility of RNAs with long tracts of poly-adenine.[8]

Drugs

IAA is also used as the reactant in the synthesis of the following list of drugs:

  1. Amixetrine
  2. Amoproxan
  3. Camylofin
  4. Fenetradil

References

  1. ^ Lide, David R., ed. (1998). Handbook of Chemistry and Physics (87 ed.). Boca Raton, Florida: CRC Press. pp. 3–374, 5–42, 6–188, 8–102, 15–22. ISBN 0-8493-0487-3.
  2. ^ Straka, M.; van Genderen, A.; Růžička, K.; Růžička, V. Heat Capacities in the Solid and in the Liquid Phase of Isomeric Pentanols. J. Chem. Eng. Data 2007, 52, 794-802.
  3. ^ a b c d e NIOSH Pocket Guide to Chemical Hazards. "#0348". National Institute for Occupational Safety and Health (NIOSH).
  4. ^ "Isoamyl alcohol". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  5. ^ a b c  One or more of the preceding sentences incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Amyl Alcohols". Encyclopædia Britannica. Vol. 1 (11th ed.). Cambridge University Press. p. 900.
  6. ^ Wilson, Calum & Davies, Noel & Corkrey, Ross & J. Wilson, Annabel & M. Mathews, Alison & C. Westmore, Guy. (2017). Receiver Operating Characteristic curve analysis determines association of individual potato foliage volatiles with onion thrips preference, cultivar and plant age. PLOS ONE. 12. e0181831. 10.1371/journal.pone.0181831.
  7. ^ Zumbo, P. "Phenol-chloroform Extraction" (PDF). WEILL CORNELL MEDICAL COLLEGE P. ZUMBO LABORATORY OF CHRISTOPHER E. MASON, PH.D. Retrieved 19 June 2014.
  8. ^ Green, Michael; Sambrook, Joseph. "Purification of Nucleic Acids: Extraction with Phenol-Chloroform". Molecular Cloning: A Laboratory Manual. Cold Spring Harbor Laboratory Press. ISBN 1936113422.