N-Butanol
Encyclopedia
n-Butanol or n-butyl alcohol or normal butanol is a primary alcohol
with a 4-carbon
structure and the molecular formula C4H9OH. Its isomer
s include isobutanol
, 2-butanol
, and tert-butanol
. Butanol is one of the group of "fusel alcohol
s" (from the German for "bad liquor"), which have more than two carbon atoms and have significant solubility in water.
n-Butanol occurs naturally as a minor product of the fermentation
of sugar
s and other carbohydrate
s, and is present in many foods and beverages. It is also a permitted artificial flavorant in the United States, used in butter, cream, fruit, rum, whiskey, ice cream and ices, candy, baked goods and cordials. It is also used in a wide range of consumer products.
The largest use of n-butanol is as an industrial intermediate, particularly for the manufacture of butyl acetate
(itself an artificial flavorant and industrial solvent). It is a petrochemical
, manufactured from propylene
and usually used close to the point of manufacture. Estimated production figures for 1997 are: United States 784,000 tonnes; Western Europe 575,000 tonnes; Japan 225,000 tonnes.
. Propylene is hydroformylated
to butyraldehyde (oxo process) in the presence of a rhodium
-based homogeneous catalyst
similar to Wilkinson's catalyst
. The butyraldehyde is then hydrogenated
to produce n-butanol.
, dibutyl phthalate
, dibutyl sebacate
, and other butyl esters, butyl ethers such as ethylene glycol monobutyl ether, di- and triethylene glycol monobutyl ether, and the corresponding butyl ether acetates. Other industrial uses include the manufacture of pharmaceuticals, polymers, pyroxylin plastics, herbicide esters (e.g., 2,4-D, 2,4,5-T) and butyl xanthate. It is also used as a diluent/reactant in the manufacture of urea
–formaldehyde
and melamine
–formaldehyde resins.
s. n-Butanol is also used as an extractant in the manufacture of antibiotic
s, hormone
s, and vitamin
s; a solvent for paints, coatings, natural resins, gums, synthetic resins, dyes, alkaloid
s, and camphor
. Other miscellaneous applications of n-butanol are as a swelling agent in textiles, as a component of brake fluid
s, cleaning formulations, degreasers, and repellents; and as a component of ore floation agents, and of wood-treating systems.
n-Butanol has been proposed as a substitute for diesel fuel and gasoline
. It is produced in small quantities in nearly all fermentation
s (see fusel oil), but species of Clostridium
produce much higher yields of butanol, and research is currently underway to increase the ultimate yield of biobutanol from biomass
.
The production or, in some cases, use of the following substances may result in exposure to n-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.
of honey bee
s contain n-butanol.
n-Butanol is used as an ingredient in processed and artificial flavourings, and for the extraction 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
.
: alcohol dehydrogenase
coverts n-butanol to butyraldehyde; this is then converted to butyric acid
by aldehyde dehydrogenase
. Butyric acid can be fully metabolized to carbon dioxide
and water
by the β-oxidation pathway, of which it is naturally the penultimate step. In the rat, only 0.03% of an oral dose of 2000 mg/kg was excreted in the urine.
The acute toxicity of n-butanol is relatively low, with oral LD50 values of 2290–4360 mg/kg (rat; comparable values for ethanol are 7000–15000 mg/kg). No deaths were reported at an inhaled concentration of 8000 ppm (4-hour exposure, rats). At sub-lethal doses, n-butanol acts as a depressant
of the central nervous system
, similar to ethanol: one study in rats indicated that the intoxicating potency of n-butanol is some six times higher than that of ethanol, possibly because of its slower transformation by alcohol dehydrogenase.
n-Butanol is a natural component of many alcoholic beverages, albeit in low (but variable) concentrations. It (along with similar fusel alcohol
s) is reputed to be responsible for severe "hangover
s", although experiments in animal models show no evidence for this. n-Butanol has occasionally been abused by alcoholics, leading to a range of adverse health effects.
With a flash point
of 29 °C (84 °F), n-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 n-butanol in enclosed spaces, although the odour threshold (0.2–30 ppm) is far below the concentration which would have any neurological effect.
n-Butanol is of low toxicity to aquatic vertebrates and invertebrates. It is rapidly biodegraded in water, although an estimated 83% partitions to air where it is degraded by hydroxyl radical
s with a half-life of 1.2–2.3 days. It has low potential to bioaccumulate
. A potential hazard of significant discharges to watercourses is the rise in chemical oxygen demand
(C.O.D.) associated with its biodegradation.
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
with a 4-carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
structure and the molecular formula C4H9OH. Its isomer
Isomer
In chemistry, isomers are compounds with the same molecular formula but different structural formulas. Isomers do not necessarily share similar properties, unless they also have the same functional groups. There are many different classes of isomers, like stereoisomers, enantiomers, geometrical...
s include isobutanol
Isobutanol
Isobutanol is an organic compound with the formula 2CHCH2OH. This colorless, flammable liquid with a characteristic smell is mainly used as a solvent. Its isomers include n-butanol, 2-butanol, and tert-butanol, all of which are more important industrially.-Production:Isobutanol is produced by the...
, 2-butanol
2-Butanol
2-Butanol, or sec-butanol, is an organic compound with formula CH3CHCH2CH3. This secondary alcohol is a flammable, colorless liquid that is soluble in 12 parts water and completely miscible with polar organic solvents such as ethers and other alcohols. It is produced on a large scale, primarily as...
, and tert-butanol
Tert-Butanol
tert-Butanol, or 2-methyl-2-propanol, is the simplest tertiary alcohol. It is one of the four isomers of butanol. tert-Butanol is a clear liquid with a camphor-like odor. It is very soluble in water and miscible with ethanol and diethyl ether...
. Butanol is one of the group of "fusel alcohol
Fusel alcohol
Fusel alcohols, also sometimes called fusel oils, or potato oil in Europe, are higher-order alcohols formed by fermentation and present in cider, mead, beer, wine, and spirits to varying degrees....
s" (from the German for "bad liquor"), which have more than two carbon atoms and have significant solubility in water.
n-Butanol occurs naturally as a minor product of the fermentation
Ethanol fermentation
Ethanol fermentation, also referred to as alcoholic fermentation, is a biological process in which sugars such as glucose, fructose, and sucrose are converted into cellular energy and thereby produce ethanol and carbon dioxide as metabolic waste products...
of sugar
Sugar
Sugar is a class of edible crystalline carbohydrates, mainly sucrose, lactose, and fructose, characterized by a sweet flavor.Sucrose in its refined form primarily comes from sugar cane and sugar beet...
s and other carbohydrate
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...
s, and is present in many foods and beverages. It is also a permitted artificial flavorant in the United States, used in butter, cream, fruit, rum, whiskey, ice cream and ices, candy, baked goods and cordials. It is also used in a wide range of consumer products.
The largest use of n-butanol is as an industrial intermediate, particularly for the manufacture of butyl acetate
Butyl acetate
n-Butyl acetate, also known as butyl ethanoate, is an organic compound commonly used as a solvent in the production of lacquers and other products. It is also used as a synthetic fruit flavoring in foods such as candy, ice cream, cheeses, and baked goods. Butyl acetate is found in many types of...
(itself an artificial flavorant and industrial solvent). It is a petrochemical
Petrochemical
Petrochemicals are chemical products derived from petroleum. Some chemical compounds made from petroleum are also obtained from other fossil fuels, such as coal or natural gas, or renewable sources such as corn or sugar cane....
, manufactured from propylene
Propylene
Propene, also known as propylene or methylethylene, is an unsaturated organic compound having the chemical formula C3H6. It has one double bond, and is the second simplest member of the alkene class of hydrocarbons, and it is also second in natural abundance.-Properties:At room temperature and...
and usually used close to the point of manufacture. Estimated production figures for 1997 are: United States 784,000 tonnes; Western Europe 575,000 tonnes; Japan 225,000 tonnes.
Production
n-Butanol is produced industrially from the petrochemical feedstock propylenePropylene
Propene, also known as propylene or methylethylene, is an unsaturated organic compound having the chemical formula C3H6. It has one double bond, and is the second simplest member of the alkene class of hydrocarbons, and it is also second in natural abundance.-Properties:At room temperature and...
. Propylene is hydroformylated
Hydroformylation
Hydroformylation, also known as oxo synthesis or oxo process, is an important industrial process for the production of aldehydes from alkenes. This chemical reaction entails the addition of a formyl group and a hydrogen atom to a carbon-carbon double bond...
to butyraldehyde (oxo process) in the presence of a rhodium
Rhodium
Rhodium is a chemical element that is a rare, silvery-white, hard and chemically inert transition metal and a member of the platinum group. It has the chemical symbol Rh and atomic number 45. It is composed of only one isotope, 103Rh. Naturally occurring rhodium is found as the free metal, alloyed...
-based homogeneous catalyst
Homogeneous catalysis
In chemistry, homogeneous catalysis is a sequence of reactions that involve a catalyst in the same phase as the reactants. Most commonly, a homogeneous catalyst is codissolved in a solvent with the reactants.-Acid catalysis:...
similar to Wilkinson's catalyst
Wilkinson's catalyst
Wilkinson's catalyst is the common name for chlorotrisrhodium, a coordination compound with the formula RhCl3 . It is named after the late organometallic chemist and 1973 Nobel Laureate, Sir Geoffrey Wilkinson who popularized its use.-Structure and basic properties:The compound is a square planar,...
. The butyraldehyde is then hydrogenated
Hydrogenation
Hydrogenation, to treat with hydrogen, also a form of chemical reduction, is a chemical reaction between molecular hydrogen and another compound or element, usually in the presence of a catalyst. The process is commonly employed to reduce or saturate organic compounds. Hydrogenation typically...
to produce n-butanol.
Industrial use
n-butanol is an intermediate in the production of butyl acrylate, butyl acetateButyl acetate
n-Butyl acetate, also known as butyl ethanoate, is an organic compound commonly used as a solvent in the production of lacquers and other products. It is also used as a synthetic fruit flavoring in foods such as candy, ice cream, cheeses, and baked goods. Butyl acetate is found in many types of...
, dibutyl phthalate
Dibutyl phthalate
Dibutyl phthalate is a commonly used plasticizer. It is also used as an additive to adhesives or printing inks. It is soluble in various organic solvents, e.g. in alcohol, ether and benzene...
, dibutyl sebacate
Dibutyl sebacate
Dibutyl sebacate is an organic chemical, a dibutyl ester of sebacic acid. Its main use is as a plasticizer in production of plastics, namely cellulose acetate butyrate, cellulose acetate propionate, ethyl cellulose, polyvinyl butyral, polyvinyl chloride, polystyrene, and many synthetic rubbers ...
, and other butyl esters, butyl ethers such as ethylene glycol monobutyl ether, di- and triethylene glycol monobutyl ether, and the corresponding butyl ether acetates. Other industrial uses include the manufacture of pharmaceuticals, polymers, pyroxylin plastics, herbicide esters (e.g., 2,4-D, 2,4,5-T) and butyl xanthate. It is also used as a diluent/reactant in the manufacture of urea
Urea
Urea or carbamide is an organic compound with the chemical formula CO2. The molecule has two —NH2 groups joined by a carbonyl functional group....
–formaldehyde
Formaldehyde
Formaldehyde is an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers...
and melamine
Melamine
Melamine is an organic base and a trimer of cyanamide, with a 1,3,5-triazine skeleton. Like cyanamide, it contains 66% nitrogen by mass and, if mixed with resins, has fire retardant properties due to its release of nitrogen gas when burned or charred, and has several other industrial uses....
–formaldehyde resins.
Other uses
n-Butanol is used as an ingredient in perfumes and as a solvent for the extraction of essential oilEssential oil
An essential oil is a concentrated hydrophobic liquid containing volatile aroma compounds from plants. Essential oils are also known as volatile oils, ethereal oils or aetherolea, or simply as the "oil of" the plant from which they were extracted, such as oil of clove...
s. n-Butanol is also used as an extractant in the manufacture of antibiotic
Antibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...
s, hormone
Hormone
A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...
s, and vitamin
Vitamin
A vitamin is an organic compound required as a nutrient in tiny amounts by an organism. In other words, an organic chemical compound is called a vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet. Thus, the term is conditional both on...
s; a solvent for paints, coatings, natural resins, gums, synthetic resins, dyes, alkaloid
Alkaloid
Alkaloids are a group of naturally occurring chemical compounds that contain mostly basic nitrogen atoms. This group also includes some related compounds with neutral and even weakly acidic properties. Also some synthetic compounds of similar structure are attributed to alkaloids...
s, and camphor
Camphor
Camphor is a waxy, white or transparent solid with a strong, aromatic odor. It is a terpenoid with the chemical formula C10H16O. It is found in wood of the camphor laurel , a large evergreen tree found in Asia and also of Dryobalanops aromatica, a giant of the Bornean forests...
. Other miscellaneous applications of n-butanol are as a swelling agent in textiles, as a component of brake fluid
Brake fluid
Brake fluid is a type of hydraulic fluid used in hydraulic brake and hydraulic clutch applications in automobiles, motorcycles, light trucks, and some bicycles. It is used to transfer force into pressure...
s, cleaning formulations, degreasers, and repellents; and as a component of ore floation agents, and of wood-treating systems.
n-Butanol has been proposed as a substitute for diesel fuel and gasoline
Gasoline
Gasoline , or petrol , is a toxic, translucent, petroleum-derived liquid that is primarily used as a fuel in internal combustion engines. It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. Some gasolines also contain...
. It is produced in small quantities in nearly all fermentation
Fermentation
Fermentation may refer to:* Fermentation , the use of fermentation in food preparation* Fermentation , a metabolic process whereby electrons released from nutrients are ultimately transferred to molecules obtained from the breakdown of those same nutrients* Fermentation , the process of...
s (see fusel oil), but species of Clostridium
Clostridium
Clostridium is a genus of Gram-positive bacteria, belonging to the Firmicutes. They are obligate anaerobes capable of producing endospores. Individual cells are rod-shaped, which gives them their name, from the Greek kloster or spindle...
produce much higher yields of butanol, and research is currently underway to increase the ultimate yield of biobutanol from biomass
Biomass
Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....
.
The production or, in some cases, use of the following substances may result in exposure to n-butanol: artificial leather
Artificial leather
Artificial leather is a fabric or finish intended to substitute for leather in fields such as upholstery, clothing and fabrics, and other uses where a leather-like finish is required but the actual material is cost-prohibitive or unsuitable....
, butyl esters, rubber cement
Rubber cement
Rubber cement is an adhesive made from elastic polymers mixed in a solvent such as acetone, hexane, heptane or toluene to keep them fluid enough to be used. Water-based formulas, often stabilised by ammonia, are also available...
, dyes, fruit essences, lacquers, motion picture, and photographic films, raincoats, perfumes, pyroxylin plastics, rayon
Rayon
Rayon is a manufactured regenerated cellulose fiber. Because it is produced from naturally occurring polymers, it is neither a truly synthetic fiber nor a natural fiber; it is a semi-synthetic or artificial fiber. Rayon is known by the names viscose rayon and art silk in the textile industry...
, safety glass, shellac
Shellac
Shellac is a resin secreted by the female lac bug, on trees in the forests of India and Thailand. It is processed and sold as dry flakes , which are dissolved in ethyl alcohol to make liquid shellac, which is used as a brush-on colorant, food glaze and wood finish...
varnish, and waterproofed cloth.
Occurrence in Nature
Alarm pheromones emitted by the Koschevnikov glandKoschevnikov gland
The Koschevnikov gland is a gland of the honeybee. It is located near the sting shaft. The gland produces an alarm pheromone which is released when a bee stings. The pheromone contains more than 40 different compounds, including pentylacetate, butylacetate, 1-hexanol, n-butanol, octanol,...
of honey bee
Honey bee
Honey bees are a subset of bees in the genus Apis, primarily distinguished by the production and storage of honey and the construction of perennial, colonial nests out of wax. Honey bees are the only extant members of the tribe Apini, all in the genus Apis...
s contain n-butanol.
Occurrence in food
n-Butanol 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. n-Butanol is also formed during deep frying of corn oil, cottonseed oil, trilinolein, and triolein.n-Butanol is used as an ingredient in processed and artificial flavourings, and for the extraction 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
Leaf protein concentrate
Leaf protein concentrate is a concentrated form of the proteins found in the leaves of plants. It has been examined as a human or animal food source, because it is potentially the cheapest, most abundant source of available protein...
.
Metabolism and toxicity
n-Butanol is readily absorbed through the intestinal tract and lungs, and also to some extent through the skin. It is metabolized completely in vertebrates in a manner similar to ethanolEthanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...
: alcohol dehydrogenase
Alcohol dehydrogenase
Alcohol dehydrogenases are a group of dehydrogenase enzymes that occur in many organisms and facilitate the interconversion between alcohols and aldehydes or ketones with the reduction of nicotinamide adenine dinucleotide...
coverts n-butanol to butyraldehyde; this is then converted to butyric acid
Butyric acid
Butyric acid , also known under the systematic name butanoic acid, is a carboxylic acid with the structural formula CH3CH2CH2-COOH. Salts and esters of butyric acid are known as butyrates or butanoates...
by aldehyde dehydrogenase
Aldehyde dehydrogenase
Aldehyde dehydrogenases are a group of enzymes that catalyse the oxidation of aldehydes.- Function :Aldehyde dehydrogenase is a polymorphic enzyme responsible for the oxidation of aldehydes to carboxylic acids, which leave the liver and are metabolized by the body’s muscle and heart...
. Butyric acid can be fully metabolized to carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
and water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
by the β-oxidation pathway, of which it is naturally the penultimate step. In the rat, only 0.03% of an oral dose of 2000 mg/kg was excreted in the urine.
The acute toxicity of n-butanol is relatively low, with oral LD50 values of 2290–4360 mg/kg (rat; comparable values for ethanol are 7000–15000 mg/kg). No deaths were reported at an inhaled concentration of 8000 ppm (4-hour exposure, rats). At sub-lethal doses, n-butanol acts as a depressant
Depressant
A depressant, or central depressant, is a drug or endogenous compound that depresses the function or activity of a specific part of the brain...
of the central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
, similar to ethanol: one study in rats indicated that the intoxicating potency of n-butanol is some six times higher than that of ethanol, possibly because of its slower transformation by alcohol dehydrogenase.
n-Butanol is a natural component of many alcoholic beverages, albeit in low (but variable) concentrations. It (along with similar fusel alcohol
Fusel alcohol
Fusel alcohols, also sometimes called fusel oils, or potato oil in Europe, are higher-order alcohols formed by fermentation and present in cider, mead, beer, wine, and spirits to varying degrees....
s) is reputed to be responsible for severe "hangover
Hangover
A hangover describes the sum of unpleasant physiological effects following heavy consumption of alcoholic beverages. The most commonly reported characteristics of a hangover include headache, nausea, sensitivity to light and noise, lethargy, dysphoria, diarrhea and thirst, typically after the...
s", although experiments in animal models show no evidence for this. n-Butanol has occasionally been abused by alcoholics, leading to a range of adverse health effects.
Other hazards
Liquid n-butanol, as is common with most organic solvents, is extremely irritating to the eyes; repeated contact with the skin can also cause irritation. 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 (>2400 ppm).With a flash point
Flash point
The flash point of a volatile material is the lowest temperature at which it can vaporize to form an ignitable mixture in air. Measuring a flash point requires an ignition source...
of 29 °C (84 °F), n-butanol presents a moderate fire hazard: it is slightly more flammable than kerosene
Kerosene
Kerosene, sometimes spelled kerosine in scientific and industrial usage, also known as paraffin or paraffin oil in the United Kingdom, Hong Kong, Ireland and South Africa, is a combustible hydrocarbon liquid. The name is derived from Greek keros...
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 n-butanol in enclosed spaces, although the odour threshold (0.2–30 ppm) is far below the concentration which would have any neurological effect.
n-Butanol is of low toxicity to aquatic vertebrates and invertebrates. It is rapidly biodegraded in water, although an estimated 83% partitions to air where it is degraded by hydroxyl radical
Hydroxyl radical
The hydroxyl radical, •OH, is the neutral form of the hydroxide ion . Hydroxyl radicals are highly reactive and consequently short-lived; however, they form an important part of radical chemistry. Most notably hydroxyl radicals are produced from the decomposition of hydroperoxides or, in...
s with a half-life of 1.2–2.3 days. It has low potential to bioaccumulate
Bioaccumulation
Bioaccumulation refers to the accumulation of substances, such as pesticides, or other organic chemicals in an organism. Bioaccumulation occurs when an organism absorbs a toxic substance at a rate greater than that at which the substance is lost...
. A potential hazard of significant discharges to watercourses is the rise in chemical oxygen demand
Chemical oxygen demand
In environmental chemistry, the chemical oxygen demand test is commonly used to indirectly measure the amount of organic compounds in water. Most applications of COD determine the amount of organic pollutants found in surface water or wastewater, making COD a useful measure of water quality...
(C.O.D.) associated with its biodegradation.