Isobutanol


Isobutanol is an organic compound with the formula 2CHCH2OH. This colorless, flammable liquid with a characteristic smell is mainly used as a solvent either directly or as its esters. Its isomers, the other butanols, include n-butanol, 2-butanol, and tert-butanol, all of which are important industrially.

Production

Isobutanol is produced by the carbonylation of propylene. Two methods are practiced industrially, hydroformylation is more common and generates a mixture of isobutyraldehydes:
The reaction is catalyzed by cobalt or rhodium complexes. The resulting aldehyde are subsequentlyhydrogenated to the alcohols, which are then separated. In Reppe carbonylation, the same products are obtained, but the hydrogenation is effected by the water-gas shift reaction.

Laboratory synthesis

and Methanol can be combined to isobutyl alcohol.

Biosynthesis of isobutanol

E. coli as well as several other organisms has been genetically modified to produce C4 alcohols from glucose, including isobutanol, 1-butanol, 2-methyl-1-butanol, 3-methyl-1-butanol, and 2-phenylethanol. The host's highly active amino acid biosynthetic pathway is shifted to alcohol production.

Applications

The uses of isobutanol and n-butanol are similar. They are often used interchangeably. The main applications are as varnishes and precursors to esters, which are useful solvents, e.g. isobutyl acetate. Isobutyl esters of phthalic, adipic, and related dicarboxylic acids are common plasticizers. Isobutanol is also a component of some biofuels.

Safety and regulation

Isobutanol is one of the least toxic of the butanols with an of 2460 mg/kg.
In March 2009, the Canadian government announced a ban on isobutanol use in cosmetics.