Amyl alcohol

There are eight isomers of amyl alcohol (C₅H₁₁OH):

• normal amyl alcohol CH₃.(CH₂)₄.OH,
• isobutyl carbinol or isoamyl alcohol (CH₃)₂.CH.CH₂.CH₂OH,
• active amyl alcohol (CH₃)(C₂H₅):CH.CH₂OH,
• tertiary butyl carbinol (CH₃)₃C.CH₂OH,
• diethyl carbinol (C₂H₅)₂CH.OH,
• methyl (n) propyl carbinol (CH₃.CH₂.CH₂)(CH₃):CH:OH,
• methyl isopropyl carbinol (CH₃)₂:CH(CH₃):CHOH, and
• dimethyl ethyl carbinol (CH₃)₂.(C₂H₅).:C.OH.

Of these alcohols, the first four are primary, the last one a tertiary, the other three secondary alcohols; three of them, viz. active amyl alcohol, methyl (n) propyl carbinol, and methyl isopropyl carbinol, contain an asymmetric carbon atom and can consequently each exist in two optically active, and one optically inactive form.

The most important is isobutyl carbinol, this being the chief constituent of fermentation amyl alcohol, and consequently a constituent of fusel oil. It may be separated from fusel oil by shaking with strong brine solution, separating the oily layer from the brine layer and distilling it, the portion boiling between 125C and 140C. being collected. For further purification it may be shaken with hot milk of lime, the oily layer separated, dried with calcium chloride and fractionated, the fraction boiling between 128C and 132C only being collected. It may be synthetically prepared from isobutyl alcohol by conversion into isovaleryl-aldehyde, which is subsequently reduced to isobutyl carbinol by means of sodium amalgam.

It is a colourless liquid of specific gravity 0.8248 (0C), boiling at 131.6C, slightly soluble in water, easily soluble in alcohol, ether, chloroform and benzene. It possesses a characteristic strong smell and a sharp burning taste. When perfectly pure, it is not a poison, although the impure product is. On passing its vapour through a red-hot tube, it undergoes decomposition with production of acetylene, ethylene, propylene, &c. It is oxidized by chromic acid mixture to isovaleryl-aldehyde; and it forms crystalline addition compounds with calcium and stannic chlorides.

The other amyl alcohols may be obtained synthetically. Of these, tertiary butyl carbinol has been the most difficult to obtain, its synthesis having only been accomplished in 1891, by L. Tissier (Comptes Rendus, 1891, 112, p. 1065) by the reduction of a mixture of trimethyl acetic acid and trimethylacetyl chloride with sodium amalgam. It is a solid which melts at 48-50C and boils at 112.3C.

(from an old encyclopedia)