1-Butanol

Since the 1950s, most 1-butanol is produced by the hydroformylation of propene (oxo process) to preferentially form the butyraldehyde n-butanal. Typical catalysts are based on cobalt and rhodium. Butyraldehyde is then hydrogenated to produce butanol. A second method for producing butanol involves the Reppe reaction of propylene with CO and water: :CH3CH=CH2 + H2O + 2 CO → CH3CH2CH2CH2OH + CO2 In former times, butanol was prepared from crotonaldehyde, which can be obtained from acetaldehyde. Butanol can also be produced by fermentation of biomass by bacteria. Prior to the 1950s, Clostridium acetobutylicum was used in industrial fermentation to produce butanol. Research in the past few decades showed results of other microorganisms that can produce butanol through fermentation. Butanol can be produced via furan hydrogenation over Pd or Pt catalyst at high temperature and high pressure. ==Industrial use==

Constituting 85% of its use, 1-butanol is mainly used in the production of varnishes. It is a popular solvent, e.g. for nitrocellulose. A variety of butanol derivatives are used as solvents, e.g. butoxyethanol or butyl acetate. Many plasticizers are based on butyl esters, e.g., dibutyl phthalate. The monomer butyl acrylate is used to produce polymers. It is the precursor to n-butylamines. The production of, or in some cases, the use of, the following substances may result in exposure to 1-butanol: artificial leather, butyl esters, rubber cement, dyes, fruit essences, lacquers, motion picture, and photographic films, raincoats, perfumes, pyroxylin plastics, rayon, safety glass, shellac varnish, and waterproofed cloth. ==Occurrence in nature==

Butan-1-ol occurs naturally as a result of carbohydrate fermentation in a number of alcoholic beverages, including beer, grape brandies, wine, and whisky. It has been detected in the volatiles of hops, jack fruit, heat-treated milks, musk melon, cheese, southern pea seed, and cooked rice. 1-Butanol is also formed during deep frying of corn oil, cottonseed oil, trilinolein, and triolein. Butan-1-ol is one of the "fusel alcohols" (from the German for "bad liquor"), which include alcohols that have more than two carbon atoms and have significant solubility in water. It is a natural component of many alcoholic beverages, albeit in low and variable concentrations. It (along with similar fusel alcohols) is reputed to be responsible for severe hangovers, although experiments in animal models show no evidence for this. 1-Butanol is used as an ingredient in processed and artificial flavorings, and for the extraction of lipid-free protein from egg yolk, natural flavouring materials and vegetable oils, the manufacture of hop extract for beermaking, and as a solvent in removing pigments from moist curd leaf protein concentrate. ==Metabolism and toxicity==

The acute toxicity of 1-butanol is relatively low, with oral LD50 values of 790–4,360 mg/kg (rat; comparable values for ethanol are 7,000–15,000 mg/kg). At sub-lethal doses, 1-butanol acts as a depressant of the central nervous system, similar to ethanol: one study in rats indicated that the intoxicating potency of 1-butanol is about 6 times higher than that of ethanol, possibly because of its slower transformation by alcohol dehydrogenase. Other hazards Liquid 1-butanol, as is common with most organic solvents, is extremely irritating to the eyes; repeated contact with the skin can also cause irritation. With a flash point of 35 °C, 1-butanol presents a moderate fire hazard: it is slightly more flammable than kerosene or diesel fuel but less flammable than many other common organic solvents. The depressant effect on the central nervous system (similar to ethanol intoxication) is a potential hazard when working with 1-butanol in enclosed spaces, although the odour threshold (0.2–30 ppm) is far below the concentration which would have any neurological effect. ==See also==