Acrylic acid (

IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is ...

: prop-2-enoic acid) is an

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

with the formula CH₂=CHCOOH. It is the simplest unsaturated

carboxylic acid In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an Substituent, R-group. The general formula of a carboxylic acid is often written as or , sometimes as with R referring to an organyl ...

, consisting of a vinyl group connected directly to a

terminus. This colorless liquid has a characteristic acrid or tart smell. It is miscible with

water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...

alcohol Alcohol may refer to: Common uses * Alcohol (chemistry), a class of compounds * Ethanol, one of several alcohols, commonly known as alcohol in everyday life ** Alcohol (drug), intoxicant found in alcoholic beverages ** Alcoholic beverage, an alco ...

ether In organic chemistry, ethers are a class of compounds that contain an ether group, a single oxygen atom bonded to two separate carbon atoms, each part of an organyl group (e.g., alkyl or aryl). They have the general formula , where R and R� ...

s, and

chloroform Chloroform, or trichloromethane (often abbreviated as TCM), is an organochloride with the formula and a common solvent. It is a volatile, colorless, sweet-smelling, dense liquid produced on a large scale as a precursor to refrigerants and po ...

. More than a million tons are produced annually.

History

The word "acrylic" was coined in 1843, for a chemical derivative of acrolein, an acrid-smelling oil derived from

glycerol Glycerol () is a simple triol compound. It is a colorless, odorless, sweet-tasting, viscous liquid. The glycerol backbone is found in lipids known as glycerides. It is also widely used as a sweetener in the food industry and as a humectant in pha ...

Production

Acrylic acid is produced by

oxidation Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is ...

propylene Propylene, also known as propene, is an unsaturated organic compound with the chemical formula . 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 petroleum-like o ...

, which is a byproduct of the production of

ethylene Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon–carbon bond, carbon–carbon doub ...

and gasoline: :

Historical methods

Because acrylic acid and its esters have long been valued commercially, many other methods have been developed. Most have been abandoned for economic or environmental reasons. An early method was the hydrocarboxylation of acetylene (" Reppe chemistry"): : This method requires

nickel carbonyl Nickel carbonyl (IUPAC name: tetracarbonylnickel) is a Organonickel chemistry, nickel(0) organometallic compound with the chemical formula, formula Ni(CO)4. This colorless liquid is the principal metal carbonyl, carbonyl of nickel. It is an React ...

, high pressures of

carbon monoxide Carbon monoxide (chemical formula CO) is a poisonous, flammable gas that is colorless, odorless, tasteless, and slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the si ...

, and acetylene, which is relatively expensive compared to propylene. Acrylic acid was once manufactured by the

hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...

of acrylonitrile, a material derived from

propene Propylene, also known as propene, is an unsaturated organic compound with the chemical formula . 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 petroleum-like od ...

by ammoxidation, but this route was abandoned because it cogenerates ammonium side products, which must be disposed of. Other now abandoned precursors to acrylic acid include ethenone and ethylene cyanohydrin.

Research

Carboxylating ethylene to acrylic acid under supercritical carbon dioxide is thermodynamically possible, but efficient catalysts have not been developed. 3-Hydroxypropionic acid (3HP), an acrylic-acid precursor by dehydration, can be produced from sugars, but the process is not competitive.

Reactions and uses

Acrylic acid undergoes the typical reactions of a carboxylic acid. When reacted with an

, it forms the corresponding

ester In chemistry, an ester is a compound derived from an acid (either organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group () of that acid is replaced by an organyl group (R). These compounds contain a distin ...

. The esters and

salt In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...

s of acrylic acid are collectively known as acrylates (or propenoates). The most common alkyl esters of acrylic acid are

methyl In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula (whereas normal methane has the formula ). In formulas, the group is often abbreviated as ...

, butyl, ethyl, and 2-ethylhexyl acrylate. Acrylic acid and its esters readily combine with themselves (to form polyacrylic acid) or other

monomer A monomer ( ; ''mono-'', "one" + '' -mer'', "part") is a molecule that can react together with other monomer molecules to form a larger polymer chain or two- or three-dimensional network in a process called polymerization. Classification Chemis ...

s (e.g. acrylamides, acrylonitrile,

vinyl Vinyl may refer to: Chemistry * Polyvinyl chloride (PVC), a particular vinyl polymer * Vinyl cation, a type of carbocation * Vinyl group, a broad class of organic molecules in chemistry * Vinyl polymer, a group of polymers derived from vinyl ...

compounds,

styrene Styrene is an organic compound with the chemical formula C6H5CH=CH2. Its structure consists of a vinyl group as substituent on benzene. Styrene is a colorless, oily liquid, although aged samples can appear yellowish. The compound evaporates easi ...

, and butadiene) by reacting at their double bond, forming homopolymers or

copolymer In polymer chemistry, a copolymer is a polymer derived from more than one species of monomer. The polymerization of monomers into copolymers is called copolymerization. Copolymers obtained from the copolymerization of two monomer species are som ...

s, which are used in the manufacture of various

plastic Plastics are a wide range of synthetic polymers, synthetic or Semisynthesis, semisynthetic materials composed primarily of Polymer, polymers. Their defining characteristic, Plasticity (physics), plasticity, allows them to be Injection moulding ...

coating A coating is a covering that is applied to the surface of an object, or substrate. The purpose of applying the coating may be decorative, functional, or both. Coatings may be applied as liquids, gases or solids e.g. powder coatings. Paints ...

adhesive Adhesive, also known as glue, cement, mucilage, or paste, is any non-metallic substance applied to one or both surfaces of two separate items that binds them together and resists their separation. The use of adhesives offers certain advantage ...

elastomer An elastomer is a polymer with viscoelasticity (i.e. both viscosity and elasticity) and with weak intermolecular forces, generally low Young's modulus (E) and high failure strain compared with other materials. The term, a portmanteau of ''ela ...

s, as well as floor polishes and paints. Acrylic acid is used in many industries, including the

diaper A diaper (, North American English) or a nappy (British English, Australian English, Hiberno-English) is a type of underwear that allows the wearer to urinate or defecate without using a toilet, by absorbing or containing waste products to p ...

industry, the

water treatment Water treatment is any process that improves the quality of water to make it appropriate for a specific end-use. The end use may be drinking, industrial water supply, irrigation, river flow maintenance, water recreation or many other uses, ...

industry, and the

textile Textile is an Hyponymy and hypernymy, umbrella term that includes various Fiber, fiber-based materials, including fibers, yarns, Staple (textiles)#Filament fiber, filaments, Thread (yarn), threads, and different types of #Fabric, fabric. ...

industry. The annual worldwide consumption of acrylic acid is projected to reach more than an estimated 8,000 kilotons by 2020. This increase is expected due to its use in new applications, including

personal care Personal care products are consumer products which are applied on various external parts of the body such as skin, hair, nails, lips, external genital and anal areas, as well as teeth and mucous membrane of the oral cavity, in order to make ...

products, detergents, and products for adult incontinence.

Substituents

As a substituent acrylic acid can be found as an acyl group or a carboxyalkyl group, depending on the removal of the group from the molecule. More specifically, these are: # The acryloyl group, with the removal of the −OH from carbon-1. # The 2-carboxyethenyl group, with the removal of a −H from carbon-3. This substituent group is found in

chlorophyll Chlorophyll is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words (, "pale green") and (, "leaf"). Chlorophyll allows plants to absorb energy ...

Safety

Acrylic acid is severely irritating and corrosive to the skin and the respiratory tract. Eye contact can result in severe and irreversible injury. Low exposure will cause minimal or no health effects, while high exposure could result in

pulmonary edema Pulmonary edema (British English: oedema), also known as pulmonary congestion, is excessive fluid accumulation in the tissue or air spaces (usually alveoli) of the lungs. This leads to impaired gas exchange, most often leading to shortness ...

. The is 340 mg/kg (rat, oral) with the lowest recorded being 293 mg/kg (oral, rat), comparable to ethylene glycol, which is indicative of being a potent poison. Ethyl acrylate was once used as a synthetic food flavoring and was withdrawn by the FDA possibly due to cancerogenic effects observed in lab animals. Animal studies showed that high doses of acrylic acid decreased weight gain. Acrylic acid can be converted to non-toxic

lactic acid Lactic acid is an organic acid. It has the molecular formula C3H6O3. It is white in the solid state and it is miscible with water. When in the dissolved state, it forms a colorless solution. Production includes both artificial synthesis as wel ...

. Acrylic acid is a constituent of tobacco smoke.

References

External links

National Pollutant Inventory: Acrylic acid
{{DEFAULTSORT:Acrylic Acid Alkenoic acids Carboxylic acid-based monomers Commodity chemicals Suspected fetotoxicants Vinyl compounds