Butyl Group

Four butyl alcohols exist, each formed by the addition of a hydroxyl group (OH) to one of the four butyl isomers discussed above. Their names and structures are as follows: n-butyl alcohol (or 1-butanol) CH₃CH₂CH₂CH₂OH; iso-butyl alcohol (or 2-methyl-1-propanol) (CH₃)₂CH CH₂OH; sec-butyl alcohol (or 2-butanol) CH₃CHOHCH₂ CH₃; tert-butyl alcohol (or 2-methyl-2-propanol) (CH₃)₃ COH.

The boiling points of the butyl alcohols decrease regularly in moving down the above list, from 244°F (118°C) for n-butyl alcohol to 226°F (108°C) for isobutyl alcohol to 212°F (100°C) for sec-butyl alcohol to 180°F (82°C) for tert-butyl alcohol. A similar pattern exists for solubility of the alcohols, increasing from 8 g per 100 g of water for n-butyl alcohol to 10 g per 100 g of water and 12.5 g per 100 g of water for the next two forms to complete miscibility for tert-butyl alcohol.

The four butyl alcohols undergo very different reactions in many instances. As an example, n-butyl and isobutyl alcohol can be oxidized rather easily to yield aldehydes. Oxidation of sec-butyl alcohol, however, results in the formation of a ketone. Oxidation of tert-butyl alcohol occurs only under the most extreme conditions, resulting in the complete oxidation of the compound to carbon dioxide and water.

Of the four butyl alcohols, n-butyl alcohol is in the greatest demand commercially. It is used as a solvent for fats, waxes, gums, shellac, varnish, and other materials in many industrial processes. It is also used as the starting point in the preparation of other butyl compounds. All of the butyl alcohols are of some interest in the synthetic flavoring industry since they can react with organic acids to make pleasant smelling esters. For example, n-butyl butanoate has the odor of pineapple; 2-methylpropyl propanoate smells like rum; 2-methylpropyl methanoate, like apple; n-butyl methanoate, like banana; and n-butyl ehtanoate, like strawberry.

The accompanying table summarizes some butyl compounds and their most important uses.