Acrylic acid (IUPAC: prop-2-enoic acid) is an organic compound with the formula CH2=CHCO2H. It is the simplest unsaturated carboxylic acid, consisting of a vinyl group connected directly to a carboxylic acid terminus. This colorless liquid has a characteristic acrid or tart smell. It is miscible with water, alcohols, ethers, and chloroform. More than one billion kilograms are produced annually.
- CH2=CHCH3 + 1.5 O2 → CH2=CHCO2H + H2O
Because acrylic acid and its esters have long been valued commercially, many other methods have been developed but most have been abandoned for economic or environmental reasons. An early method was the hydrocarboxylation of acetylene ("Reppe chemistry"):
- HCCH + CO + H2O → CH2=CHCO2H
This method requires nickel carbonyl and high pressures of carbon monoxide. It was once manufactured by the hydrolysis of acrylonitrile which is derived from propene by ammoxidation, but was abandoned because the method cogenerates ammonium derivatives. Other now abandoned precursors to acrylic acid include ethenone and ethylene cyanohydrin.
Dow Chemical Company and a partner, OPX Biotechnologies, are investigating using fermented sugar to produce 3-hydroxypropionic acid (3HP), an acrylic acid precursor.  The goal is to reduce greenhouse gas emissions. 
Reactions and uses
Acrylic acid undergoes the typical reactions of a carboxylic acid and, when reacted with an alcohol, it will form the corresponding ester. The esters and salts of acrylic acid are collectively known as acrylates (or propenoates). The most common alkyl esters of acrylic acid are methyl-, butyl-, ethyl-, and 2-ethylhexyl-acrylate.
Acrylic acid and its esters readily combine with themselves (to form polyacrylic acid) or other monomers (e.g. acrylamides, acrylonitrile, vinyl, styrene, and butadiene) by reacting at their double bond, forming homopolymers or copolymers which are used in the manufacture of various plastics, coatings, adhesives, elastomers, as well as floor polishes, and paints.
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.
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. The LD50 is 340 mg/kg (rat, oral).
- Merck Index, 11th Edition, 124.
- Dippy, J.F.J., Hughes, S.R.C., Rozanski, A., J. Chem Soc., 1959, 2492.
- Takashi Ohara, Takahisa Sato, Noboru Shimizu, Günter Prescher Helmut Schwind, Otto Weiberg, Klaus Marten, Helmut Greim “Acrylic Acid and Derivatives” in Ullmann's Encyclopedia of Industrial Chemistry 2003, Wiley-VCH, Weinheim. doi: 10.1002/14356007.a01_161.pub2
- Sweet Deal: Dow and Partner Cook up Sugar-to-Acrylic Plan. Durabilityanddesign.com. Retrieved on 2012-05-24.
- Better Bugs to Make Plastics, Technology Review, September 20, 2010, retrieved January 9, 2012. Technologyreview.com (2010-09-20). Retrieved on 2012-05-24.