Methacrylic acid

Methacrylic acid, abbreviated MAA, is an organic compound. This colorless, viscous liquid is a carboxylic acid with an acrid unpleasant odor. It is soluble in warm water and miscible with most organic solvents. Methacrylic acid is produced industrially on a large scale as a precursor to its esters, especially methyl methacrylate (MMA), and to poly(methyl methacrylate) (PMMA).

Methacrylic acid
Structural formula of methacrylic acid
Ball-and-stick model of the methacrylic acid molecule
Names
IUPAC name
Methacrylic acid[1]
Preferred IUPAC name
2-Methylprop-2-enoic acid
Other names
Methacrylic acid
2-Methyl-2-propenoic acid
α-Methacrylic acid
2-Methylacrylic acid
2-Methylpropenoic acid
Identifiers
3D model (JSmol)
Abbreviations MAA
ChEBI
ChemSpider
ECHA InfoCard 100.001.096
EC Number
  • 201-204-4
MeSH C008384
UNII
  • InChI=1S/C4H6O2/c1-3(2)4(5)6/h1H2,2H3,(H,5,6)
    Key: CERQOIWHTDAKMF-UHFFFAOYSA-N
  • CC(C(O)=O)=C
Properties
C4H6O2
Molar mass 86.09 g/mol
Appearance Colorless liquid or solid
Odor Acrid, repulsive[2]
Density 1.015 g/cm3
Melting point 14 to 15 °C (57 to 59 °F; 287 to 288 K)
Boiling point 161 °C (322 °F; 434 K)
9% (25 °C)[2]
Vapor pressure 0.7 mmHg (20 °C)[2]
Hazards
NFPA 704 (fire diamond)
3
2
2
Flash point 77.2 °C (171.0 °F; 350.3 K)
NIOSH (US health exposure limits):
PEL (Permissible)
 none[2]
REL (Recommended)
 TWA 20 ppm (70 mg/m3) [skin][2]
IDLH (Immediate danger)
 N.D.[2]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)
Infobox references

Production

In the most common route, methacrylic acid is prepared from acetone cyanohydrin, which is converted to methacrylamide sulfate using sulfuric acid. This derivative in turn is hydrolyzed to methacrylic acid, or esterified to methyl methacrylate in one step. Another route to methacrylic acid starts with isobutylene, which obtainable by dehydration of tert-butanol. Isobutylene is oxidized sequentially to methacrolein and then methacrylic acid. Methacrolein for this purpose can also be obtained from formaldehyde and ethylene. Yet a third route involves the dehydrogenation of Isobutyric acid.[3]

Various green routes have been explored but they have not been commercialized. Specifically, the decarboxylation of itaconic acid, citraconic acid, and mesaconic acids affords methacrylic acid. Salts of methacrylic acid have been obtained by boiling citra- or meso-brompyrotartaric acids with alkalis.

Pyrolysis of ethyl methacrylate efficiently gives methacrylic acid.[4]

Uses and occurrence

Of course, the main use of MAA is its polymerization to poly(methyl methacrylate).[5]

Methacrylic acid is used in some nail primers to help acrylic nails adhere to the nail plate.[6]

MAA occurs naturally in small amounts in the oil of Roman chamomile.

Reactions

For a commercial applications, MMA is polymerized using azobisisobutyronitrile as a thermally activated free-radical catalyst. Otherwise, MMA is relatively slow to polymerize thermally or photochemically.[5]

Methacrylic acid undergoes several reactions characteristic of alpha,beta-unsaturated acids (see acrylic acid). These reactions include the Diels–Alder reaction and Michael additions. Esterifications are brought about by acid-catalyzed condensations with alcohols, alkylations with certain alkenes, and transesterifications. Epoxide ring-opening gives hydroxyalkyl esters.[3] Sodium amalgam reduces it to isobutyric acid. A polymeric form of methacrylic acid was described in 1880.[7]

See also
Typical vinyl ester resin derived from bisphenol A diglycidyl ether and methacrylic acid.[8]

References
  1. International Union of Pure and Applied Chemistry (2014). Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013. The Royal Society of Chemistry. p. 746. doi:10.1039/9781849733069. ISBN 978-0-85404-182-4.
  2. NIOSH Pocket Guide to Chemical Hazards. "#0386". National Institute for Occupational Safety and Health (NIOSH).
  3. William Bauer, Jr. (2002). "Methacrylic Acid and Derivatives". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a16_441.{{cite encyclopedia}}: CS1 maint: uses authors parameter (link)
  4. W. P. Ratchford (1949). "Acrylic Acid I. Pyrolysis Method". Organic Syntheses. 29: 2. doi:10.15227/orgsyn.029.0002. This article also describes pyrolysis of ethyl methacrylate.
  5. Stickler, Manfred; Rhein, Thoma (2000). "Polymethacrylates". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a21_473. ISBN 3527306730.
  6. "Products - Nail Care Products". www.fda.gov. U.S. Food and Drug Administration. 2018-03-06. Retrieved 2019-04-03.
  7. F. Engelhorn (1880). Rudolph Fittig (ed.). "II. Untersuchungen über die ungesättigten Säuren. Zur Kenntnis der Methacrylsäure" [II. Investigations on the unsaturated acids. On the characterisation of methacrylic acid.]. Justus Liebigs Annalen der Chemie. 200: 70. doi:10.1002/jlac.18802000103..
  8. Pham, Ha Q.; Marks, Maurice J. (2012). "Epoxy Resins". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a09_547.pub2. ISBN 978-3527306732.
  • Methacrylic Acid in Europe.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.