Isoamyl Alcohol
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Isoamyl alcohol is a colorless liquid with the formula , specifically (H3C–)2CH–CH2–CH2–OH. It is one of several
isomer In chemistry, isomers are molecules or polyatomic ions with identical molecular formula – that is, the same number of atoms of each element (chemistry), element – but distinct arrangements of atoms in space. ''Isomerism'' refers to the exi ...
s of
amyl alcohol Amyl alcohols are alcohols with the formula C5H11OH. Eight are known. A mixture of amyl alcohols (also called amyl alcohol) can be obtained from fusel alcohol. Amyl alcohol is used as a solvent and in esterification, by which is produced amy ...
(pentanol). It is also known as isopentyl alcohol, isopentanol, or (in the
IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is ...
recommended nomenclature) 3-methyl-butan-1-ol. An obsolete name for it was isobutyl carbinol. Isoamyl alcohol is an ingredient in the production of banana oil, an
ester In chemistry, an ester is a compound derived from an acid (either organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group () of that acid is replaced by an organyl group (R). These compounds contain a distin ...
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 ''Tuber melanosporum'', called the black truffle, Périgord truffle or French black truffle, is a species of truffle native to Southern Europe. It is one of the most expensive edible fungi in the world. In 2013, the truffle cost between 1,000 a ...
'', 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 A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...
used by
hornet Hornets (insects in the genus ''Vespa'') are the largest of the Eusociality, eusocial wasps, and are similar in appearance to yellowjackets, their close relatives. Some species can reach up to in length. They are distinguished from other Vespi ...
s to attract other members of the hive to attack.


Extraction from fusel oil

Isoamyl alcohol can be separated from fusel oil by either of two methods: shaking with strong
brine Brine (or briny water) is a high-concentration solution of salt (typically sodium chloride or calcium chloride) in water. In diverse contexts, ''brine'' may refer to the salt solutions ranging from about 3.5% (a typical concentration of seawat ...
solution and separating the oily layer from the brine layer;
distilling Distillation, also classical distillation, is the process of separating the component substances of a liquid mixture of two or more chemically discrete substances; the separation process is realized by way of the selective boiling of the mixt ...
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 Calcium chloride is an inorganic compound, a Salt (chemistry), salt with the chemical formula . It is a white crystalline solid at room temperature, and it is highly soluble in water. It can be created by neutralising hydrochloric acid with cal ...
, and distilling it, collecting the fraction boiling between 128 and 132 °C.


Synthesis

Isoamyl alcohol can be synthesized by condensation of
isobutene Isobutylene (or 2-methylpropene) is a hydrocarbon with the chemical formula . It is a four-carbon branched alkene (olefin), one of the four isomers of butylene. It is a colorless flammable gas, and is of considerable industrial value. Productio ...
and
formaldehyde Formaldehyde ( , ) (systematic name methanal) is an organic compound with the chemical formula and structure , more precisely . The compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde. It is stored as ...
which produces isoprenol, then
hydrogenation Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to redox, reduce or Saturated ...
. 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 Acetylene (Chemical nomenclature, systematic name: ethyne) is a chemical compound with the formula and structure . It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is u ...
,
ethylene Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon–carbon bond, carbon–carbon doub ...
,
propylene Propylene, also known as propene, is an unsaturated organic compound with the chemical formula . It has one double bond, and is the second simplest member of the alkene class of hydrocarbons. It is a colorless gas with a faint petroleum-like o ...
, and other compounds. It is
oxidized Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is ...
by
chromic acid Chromic acid is a chemical compound with the chemical formula . It is also a jargon for a solution formed by the addition of sulfuric acid to aqueous solutions of dichromate. It consists at least in part of chromium trioxide. The term "chromic ...
to isovaleraldehyde, and it forms addition compounds
crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...
s with calcium chloride and
tin(IV) chloride Tin(IV) chloride, also known as tin tetrachloride or stannic chloride, is an inorganic compound of tin and chlorine with the formula SnCl4. It is a colorless hygroscopic liquid, which fumes on contact with air. It is used as a precursor to other ...
.


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 A defoamer or an anti-foaming agent is a chemical additive that reduces and hinders the formation of foam in industrial process liquids. The terms anti-foam agent and defoamer are often used interchangeably. Strictly speaking, defoamers eliminat ...
in the chloroform isoamyl alcohol reagent. Isoamyl alcohol is used in a
phenol–chloroform extraction Phenol–chloroform extraction is a liquid-liquid extraction technique in molecular biology used to separate nucleic acids from proteins and lipids. Process Aqueous samples, lysed cells, or homogenised tissue are mixed with equal volumes of a phen ...
mixed with the chloroform to further inhibit RNase activity and prevent solubility of RNAs with long tracts of poly-
adenine Adenine (, ) (nucleoside#List of nucleosides and corresponding nucleobases, symbol A or Ade) is a purine nucleotide base that is found in DNA, RNA, and Adenosine triphosphate, ATP. Usually a white crystalline subtance. The shape of adenine is ...
.


Drugs

IAA is also used as the reactant in the synthesis of the following list of drugs: # Amixetrine # Amoproxan # Camylofin # Fenetradil


References

{{Alcohols Primary alcohols Alkanols Isopentyl compounds