Butanol (also called butyl alcohol) is a four-carbon

alcohol Alcohol most commonly refers to: * Alcohol (chemistry), an organic compound in which a hydroxyl group is bound to a carbon atom * Alcohol (drug), an intoxicant found in alcoholic drinks Alcohol may also refer to: Chemicals * Ethanol, one of sev ...

with a

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwe ...

of C₄ H₉ O H, which occurs in five

isomer In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers. Is ...

ic structures (four structural isomers), from a straight-chain primary alcohol to a branched-chain tertiary alcohol; all are a

butyl In organic chemistry, butyl is a four- carbon alkyl radical or substituent group with general chemical formula , derived from either of the two isomers (''n''-butane and isobutane) of butane. The isomer ''n''-butane can connect in two ways, gi ...

or isobutyl group linked to a

hydroxyl In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydrox ...

group (sometimes represented as BuOH, ''n''-BuOH, ''i''-BuOH, and ''t''-BuOH). These are ''n''-butanol, 2 stereoisomers of sec-butanol, isobutanol and ''tert''-butanol. Butanol is primarily used as a

solvent A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...

and as an intermediate in

chemical synthesis As a topic of chemistry, chemical synthesis (or combination) is the artificial execution of chemical reactions to obtain one or several products. This occurs by physical and chemical manipulations usually involving one or more reactions. In mod ...

, and may be used as a

fuel A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work. The concept was originally applied solely to those materials capable of releasing chemical energy b ...

. Biologically produced butanol is called biobutanol, which may be ''n''-butanol or isobutanol.

Isomers

The unmodified term ''butanol'' usually refers to the straight chain isomer with the alcohol

functional group In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the r ...

at the terminal carbon, which is also known as ''n''-butanol or 1-butanol. The straight chain isomer with the alcohol at an internal carbon is ''sec''-butanol or

2-butanol 2-Butanol, or ''sec''-butanol, is an organic compound with formula C H3CH( OH)CH2CH3. Its structural isomers are 1-butanol. isobutanol, and ''tert''-butanol. 2-Butanol is chiral and thus can be obtained as either of two stereoisomers designa ...

. The branched isomer with the alcohol at a terminal carbon is isobutanol or 2-methyl-1-propanol, and the branched isomer with the alcohol at the internal carbon is ''tert''-butanol or 2-methyl-2-propanol. The butanol isomers have different melting and boiling points. ''n''-butanol and isobutanol have limited solubility, ''sec''-butanol has substantially greater solubility, while ''tert''-butanol is

miscible Miscibility () is the property of two substances to mix in all proportions (that is, to fully dissolve in each other at any concentration), forming a homogeneous mixture (a solution). The term is most often applied to liquids but also applies ...

with water. The hydroxyl group makes the molecule polar, promoting solubility in water, while the longer hydrocarbon chain mitigates the polarity and reduces solubility.

Toxicity

Butanol exhibits a low order of toxicity in single dose experiments with laboratory animals and is considered safe enough for use in cosmetics. Brief, repeated overexposure with the skin can result in depression of the central nervous system, as with other short-chain alcohols. Exposure may also cause severe eye irritation and moderate skin irritation. The main dangers are from prolonged exposure to the alcohol's vapors. In extreme cases this includes suppression of the

central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...

and even death. Under most circumstances, butanol is quickly metabolized to

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...

. It has not been shown to damage DNA or cause

cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...

Uses

Primary uses

Butanol is used as a

for a wide variety of chemical and textile processes, in organic synthesis, and as a chemical intermediate. It is also used as a

paint thinner A paint thinner is a solvent used to thin oil-based paints. Solvents labeled "paint thinner" are usually mineral spirits having a flash point at about 40 °C (104 °F), the same as some popular brands of charcoal starter. Common sol ...

and a solvent in other coating applications where a relatively slow evaporating latent solvent is preferable, as with lacquers and ambient-cured enamels. It is also used as a component of

hydraulic Hydraulics (from Greek: Υδραυλική) is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counte ...

and

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, and to amplify braking force. It works ...

s. A 50% solution of butanol in water has been used since the 20th century to retard the drying of fresh plaster in

fresco Fresco (plural ''frescos'' or ''frescoes'') is a technique of mural painting executed upon freshly laid ("wet") lime plaster. Water is used as the vehicle for the dry-powder pigment to merge with the plaster, and with the setting of the plast ...

painting. The solution is usually sprayed on the wet plaster after the plaster has been trowelled smooth and extends the working period during which frescos can be painted up to 18 hours. Butanol is used in the synthesis of

2-butoxyethanol 2-Butoxyethanol is an organic compound with the chemical formula BuOC2H4OH (Bu = CH3CH2CH2CH2). This colorless liquid has a sweet, ether-like odor, as it derives from the family of glycol ethers, and is a butyl ether of ethylene glycol. As a rela ...

. A major application for butanol is as a reactant with acrylic acid to produce butyl acrylate, a primary ingredient of water based acrylic paint. It is also used as a base for perfumes, but on its own has a highly alcoholic aroma. Salts of butanol are chemical intermediates; for example,

alkali metal The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K),The symbols Na and K for sodium and potassium are derived from their Latin names, ''natrium'' and ''kalium''; these are still the origins of the names ...

salts of ''tert''-butanol are ''tert''-butoxides.

Recreational Use

Butanol is a central nervous system

depressant A depressant, or central depressant, is a drug that lowers neurotransmission levels, which is to depress or reduce arousal or stimulation, in various areas of the brain. Depressants are also colloquially referred to as downers as they lower the ...

. It can have effects similar to

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...

when ingested or drunk by living beings such as humans.

Biobutanol

Butanol (''n''-butanol or isobutanol) is a potential

biofuel Biofuel is a fuel that is produced over a short time span from biomass, rather than by the very slow natural processes involved in the formation of fossil fuels, such as oil. According to the United States Energy Information Administration ...

( butanol fuel). Butanol at 85 percent concentration can be used in cars designed for gasoline (petrol) without any change to the engine (unlike 85% ethanol), and it contains more energy for a given volume than ethanol and almost as much as gasoline, and 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. Photoautotrophic microorganisms, like cyanobacteria, can be engineered to produce 1-butanol indirectly from and water.Liu, X., Miao, R., Lindberg, P., & Lindblad, P. (2019). Modular engineering for efficient photosynthetic biosynthesis of 1-butanol from CO 2 in cyanobacteria. Energy & Environmental Science, 12(9), 2765-2777.

Production

Since the 1950s, most butanol in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

is produced commercially from

fossil fuel A fossil fuel is a hydrocarbon-containing material formed naturally in the Earth's crust from the remains of dead plants and animals that is extracted and burned as a fuel. The main fossil fuels are coal, oil, and natural gas. Fossil fuels ma ...

s. The most common process starts with

propene Propylene, also known as propene, is an unsaturated organic compound with the chemical formula CH3CH=CH2. It has one double bond, and is the second simplest member of the alkene class of hydrocarbons. It is a colorless gas with a faint petrol ...

(propylene), which is put through a

hydroformylation Hydroformylation, also known as oxo synthesis or oxo process, is an industrial process for the production of aldehydes from alkenes. This chemical reaction entails the net addition of a formyl group (CHO) and a hydrogen atom to a carbon-carbon ...

reaction to form butanal, which is then reduced with

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-to ...

to 1-butanol and/or 2-butanol. ''tert''-butanol is derived from

isobutane Isobutane, also known as ''i''-butane, 2-methylpropane or methylpropane, is a chemical compound with molecular formula HC(CH3)3. It is an isomer of butane. Isobutane is a colourless, odourless gas. It is the simplest alkane with a tertiary carbo ...

as a co-product of propylene oxide production. Propen Hydroformylierung zu Butanol

Butanol can also be produced by

fermentation Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food p ...

biomass Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms bio ...

by bacteria. Prior to the 1950s, ''

Clostridium acetobutylicum ''Clostridium acetobutylicum'', ATCC 824, is a commercially valuable bacterium sometimes called the "Weizmann Organism", after Jewish Russian-born biochemist Chaim Weizmann. A senior lecturer at the University of Manchester, England, he used th ...

'' was used in industrial fermentation to produce ''n''-butanol.

References

*''Merck Index'', 12th Edition, 1575. {{Authority control Alkanols Alcohol solvents Fatty alcohols Biotechnology products Liquid fuels Oxygenates