Isobutanol
Isobutanol (IUPAC nomenclature: 2-methylpropan-1-ol) is an organic compound with the formula (CH)CHCHOH (sometimes represented as "i"-BuOH). This colorless, flammable liquid with a characteristic smell is mainly used as a solvent either directly or as its esters. Its isomers are 1-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 isobutyraldehyde and butyraldehyde: The reaction is catalyzed by cobalt or rhodium complexes. The resulting aldehydes are hydrogenated 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. Propanol and methanol can be reacted to produce isobutyl alcohol via Guerbet condensation. 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. α-Ketoisovalerate, derived from valine, is prone to decarboxylation to give isobutyraldehyde, which is susceptible to reduction  to the alcohol: 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 (rat, oral). In March 2009, the Government of Canada announced a ban on isobutanol use in cosmetics.