1-Butanol occurs naturally as a minor product of the ethanol fermentationofsugars and other saccharides[6] and is present in many foods and drinks.[7][8] It is also a permitted artificial flavorant in the United States,[9] used in butter, cream, fruit, rum, whiskey, ice cream and ices, candy, baked goods, and cordials.[10] It is also used in a wide range of consumer products.[7]
The largest use of 1-butanol is as an industrial intermediate, particularly for the manufacture of butyl acetate (itself an artificial flavorant and industrial solvent). It is a petrochemical derived from propylene. Estimated production figures for 1997 are: United States 784,000 tonnes; Western Europe 575,000 tonnes; Japan 225,000 tonnes.[8]
Since the 1950s, most 1-butanol is produced by the hydroformylationofpropene (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:[11]
Butanol can also be produced by fermentationofbiomass 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.
1-Butanol has been proposed as a substitute for diesel fuel and gasoline. It is produced in small quantities in nearly all fermentations (see fusel oil). Clostridium produces much higher yields of butanol. Research is underway to increase the biobutanol yield from biomass.
Butanol is considered as a potential biofuel (butanol fuel). Butanol at 85 percent strength can be used in cars designed for gasoline without any change to the engine (unlike 85% ethanol), and it provides more energy for a given volume than ethanol, almost as much as gasoline. Therefore, a vehicle using butanol would return fuel consumption more comparable to gasoline than ethanol. Butanol can also be added to diesel fuel to reduce soot emissions.[12]
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.[7]
Butan-1-ol occurs naturally as a result of carbohydrate fermentation in a number of alcoholic beverages, including beer,[13] grape brandies,[14] wine,[15] and whisky.[16] It has been detected in the volatiles of hops,[17] jack fruit,[18] heat-treated milks,[19] musk melon,[20] cheese,[21] southern pea seed,[22] and cooked rice.[23] 1-Butanol is also formed during deep frying of corn oil, cottonseed oil, trilinolein, and triolein.[24]
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.[25] It is a natural component of many alcoholic beverages, albeit in low and variable concentrations.[26][27] It (along with similar fusel alcohols) is reputed to be responsible for severe hangovers, although experiments in animal models show no evidence for this.[28]
1-Butanol is used as an ingredient in processed and artificial flavorings,[29] and for the extraction of lipid-free protein from egg yolk,[30] 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.[31]
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).[8][32][11] It is metabolized completely in vertebrates in a manner similar to ethanol: alcohol dehydrogenase converts 1-butanol to butyraldehyde; this is then converted to butyric acidbyaldehyde dehydrogenase. Butyric acid can be fully metabolized to carbon dioxide and water by the β-oxidation pathway. In the rat, only 0.03% of an oral dose of 2,000 mg/kg was excreted in the urine.[33] 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.[34]
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.[8] This is believed to be a generic effect of defatting. No skin sensitization has been observed. Irritation of the respiratory pathways occurs only at very high concentrations (>2,400 ppm).[35]
With a flash point of 35 °C, 1-butanol presents a moderate fire hazard: it is slightly more flammable than keroseneordiesel 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.[35][36]
^[n-Butanol Product Information, The Dow Chemical Company, Form No. 327-00014-1001, page 1]
^Dubey, Gyan (2008). "Study of densities, viscosities, and speeds of sound of binary liquid mixtures of butan-1-ol with n-alkanes (C6, C8, and C10) at T = (298.15, 303.15, and 308.15) K". The Journal of Chemical Thermodynamics. 40 (2): 309–320. doi:10.1016/j.jct.2007.05.016.
^Hazelwood, Lucie A.; Daran, Jean-Marc; van Maris, Antonius J. A.; Pronk, Jack T.; Dickinson, J. Richard (2008), "The Ehrlich pathway for fusel alcohol production: a century of research on Saccharomyces cerevisiae metabolism", Appl. Environ. Microbiol., 74 (8): 2259–66, Bibcode:2008ApEnM..74.2259H, doi:10.1128/AEM.02625-07, PMC2293160, PMID18281432.
^ abcdn-Butanol(PDF), SIDS Initial Assessment Report, Geneva: United Nations Environment Programme, April 2005.
^21 C.F.R. § 172.515; 42 FR 14491, Mar. 15, 1977, as amended.
^Hall, R. L.; Oser, B. L. (1965), "Recent progress in the consideration of flavouring ingredients under the food additives amendment. III. Gras substances", Food Technol.: 151, cited in Butanols: four isomers, Environmental Health Criteria monograph No. 65, Geneva: World Health Organization, 1987, ISBN92-4-154265-9.
^Bonte, W. (1979), "Congener substances in German and foreign beers", Blutalkohol, 16: 108–24, cited in Butanols: four isomers, Environmental Health Criteria monograph No. 65, Geneva: World Health Organization, 1987, ISBN92-4-154265-9.
^Schreier, Peter; Drawert, Friedrich; Winkler, Friedrich (1979), "Composition of neutral volatile constituents in grape brandies", J. Agric. Food Chem., 27 (2): 365–72, doi:10.1021/jf60222a031.
^Bonte, W. (1978), "Congener content of wine and similar beverages", Blutalkohol, 15: 392–404, cited in Butanols: four isomers, Environmental Health Criteria monograph No. 65, Geneva: World Health Organization, 1987, ISBN92-4-154265-9.
^Postel, W.; Adam, L. (1978), "Gas chromatographic characterization of whiskey. III. Irish whiskey", Branntweinwirtschaft, 118: 404–7, cited in Butanols: four isomers, Environmental Health Criteria monograph No. 65, Geneva: World Health Organization, 1987, ISBN92-4-154265-9.
^Tressl, Roland; Friese, Lothar; Fendesack, Friedrich; Koeppler, Hans (1978), "Studies of the volatile composition of hops during storage", J. Agric. Food Chem., 26 (6): 1426–30, doi:10.1021/jf60220a036.
^Swords, G.; Bobbio, P. A.; Hunter, G. L. K. (1978), "Volatile constituents of jack fruit (Arthocarpus heterophyllus)", J. Food Sci., 43 (2): 639–40, doi:10.1111/j.1365-2621.1978.tb02375.x.
^Jaddou, Haytham A.; Pavey, John A.; Manning, Donald J. (1978), "Chemical analysis of flavor volatiles in heat-treated milks", J. Dairy Res., 45 (3): 391–403, doi:10.1017/S0022029900016617, S2CID85985458.
^Yabumoto, K.; Yamaguchi, M.; Jennings, W. G. (1978), "Production of volatile compounds by Muskmelon, Cucumis melo", Food Chem., 3 (1): 7–16, doi:10.1016/0308-8146(78)90042-0.
^Dumont, Jean Pierre; Adda, Jacques (1978), "Occurrence of sesquiterpones in mountain cheese volatiles", J. Agric. Food Chem., 26 (2): 364–67, doi:10.1021/jf60216a037.
^Fisher, Gordon S.; Legendre, Michael G.; Lovgren, Norman V.; Schuller, Walter H.; Wells, John A. (1979), "Volatile constituents of southernpea seed [Vigna unguiculata (L.) Walp.]", J. Agric. Food Chem., 27 (1): 7–11, doi:10.1021/jf60221a040.
^Chang, S. S.; Peterson, K. J.; Ho, C. (1978), "Chemical reactions involved in the deep-fat frying of foods", J. Am. Oil Chem. Soc., 55 (10): 718–27, doi:10.1007/BF02665369, PMID730972, S2CID97273264, cited in Butanols: four isomers, Environmental Health Criteria monograph No. 65, Geneva: World Health Organization, 1987, ISBN92-4-154265-9.
^Woo, Kang-Lyung (2005), "Determination of low molecular weight alcohols including fusel oil in various samples by diethyl ether extraction and capillary gas chromatography", J. AOAC Int., 88 (5): 1419–27, doi:10.1093/jaoac/88.5.1419, PMID16385992.
^Mellan, I. (1950), Industrial Solvents, New York: Van Nostrand Reinhold, pp. 482–88, cited in Butanols: four isomers, Environmental Health Criteria monograph No. 65, Geneva: World Health Organization, 1987, ISBN92-4-154265-9.
^Meslar, Harry W.; White, Harold B. III (1978), "Preparation of lipid-free protein extracts of egg yolk", Anal. Biochem., 91 (1): 75–81, doi:10.1016/0003-2697(78)90817-5, PMID9762085.
^Bray, Walter J.; Humphries, Catherine (1978), "Solvent fractionation of leaf juice to prepare green and white protein products", J. Sci. Food Agric., 29 (10): 839–46, Bibcode:1978JSFA...29..839B, doi:10.1002/jsfa.2740291003.
^Ethanol(PDF), SIDS Initial Assessment Report, Geneva: United Nations Environment Programme, August 2005.
^Gaillard, D.; Derache, R. (1965), "Métabilisation de différents alcools présents dans les biossons alcooliques chez le rat", Trav. Soc. Pharmacol. Montpellier, 25: 541–62, cited in Butanols: four isomers, Environmental Health Criteria monograph No. 65, Geneva: World Health Organization, 1987, ISBN92-4-154265-9.
^ abWysocki, C. J.; Dalton, P. (1996), Odor and Irritation Thresholds for 1-Butanol in Humans, Philadelphia: Monell Chemical Senses Center, cited in n-Butanol(PDF), SIDS Initial Assessment Report, Geneva: United Nations Environment Programme, April 2005.
