4,4′-Methylenedianiline (MDA) is an organic compound with the formula CH2(C6H4NH2)2. It is a colorless solid, although commercial samples can appear yellow or brown. It is produced on an industrial scale, mainly as a precursor to polyurethanes.

Synthesis and applications

In the industrial production, MDA is produced by reaction of formaldehyde and aniline in the presence of hydrochloric acid.[3]

MDA is a common monomer in the synthesis of polymer materials. These include polyamides,[4] polyimides and polyimines.[5] MDA is also used extensively as a precursor to methylene diphenyl diisocyanate (MDI). Here, MDA is treated with phosgene to produce MDI. MDI, in turn, is a precursor to many polyurethane foams.[6][7] Lower quantities are used as hardeners in epoxy resins and adhesives, as well as in the production of high-performance polymers.[3] Additionally, hydrogenation of MDA can be performed to produce 4,4,diaminodicyclohexylmethane, which is also used in polymer chemistry.[8]

MDA can also be applied as a bidentate (bridging) ligand in the formation of metal-coordination complexes.[9]

Safety

MDA is considered a potential occupational carcinogen by the US National Institute for Occupational Safety and Health. The Occupational Safety and Health Administration has set a permissible exposure limit at 0.01 ppm over an eight-hour time-weighted average, and a short-term exposure limit at 0.1 ppm.[10]

It is suspected carcinogen.[6] It is included in the "substances of very high concern" list of the European Chemicals Agency (ECHA).[7] The compound was blamed in a mass poisoning in the vicinity of Epping, Essex, United Kingdom during 1965 during which 84 individuals were poisoned through accidental contamination of flour used to make bread.[11]

References

  1. ^ a b c d e f g NIOSH Pocket Guide to Chemical Hazards. "#0415". National Institute for Occupational Safety and Health (NIOSH).
  2. ^ a b Record of 4,4'-Diaminodiphenylmethane in the GESTIS Substance Database of the Institute for Occupational Safety and Health, accessed on 12 February 2021.
  3. ^ a b "Data on manufacture, import, export, uses and release of 4-4' diaminodiphenylmethane" (PDF). Archived from the original (PDF) on 2011-10-01.
  4. ^ Endo T, Higashihara T (2022). "Direct Synthesis of Thermally Stable Semiaromatic Polyamides by Bulk Polymerization Using Aromatic Diamines and Aliphatic Dicarboxylic Acids". ACS Omega. 7 (10): 8753–8758. doi:10.1021/acsomega.1c06983. PMC 8928493. PMID 35309482.
  5. ^ Schoustra S, De Heer Kloots M, Posthuma J, Van Doorn D, Dijksman J, Smulders M (2022). "Raman Spectroscopy Reveals Phase Separation in Imine-Based Covalent Adaptable Networks". Macromolecules. 55 (23): 10341–10355. Bibcode:2022MaMol..5510341S. doi:10.1021/acs.macromol.2c01595. PMC 9753755. PMID 36530523.
  6. ^ a b "ToxFAQs for 4,4'-Methylenedianiline". Agency for Toxic Substances and Disease Registry.
  7. ^ a b "Background document for 4,4'-Diaminodiphenylmethane (MDA)" (PDF). European Chemicals Agency. Archived from the original (PDF) on 2017-08-22. Retrieved 2015-02-24.
  8. ^ Roose P, Eller K, Henkes E, Rossbacher R, Höke H (2005). "Amines, Aliphatic". Ullmann’s Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a02_001. ISBN 3-527-30673-0.
  9. ^ Chisca D, Croitor L, Melnic E, Petuhov O, Kulikova O, Fonari MS (2020). "Six transition metal–organic materials with the ditopic 4,4′-diaminodiphenylmethane ligand: Synthesis, structure characterization and luminescent properties". Polyhedron. 192: 114844. doi:10.1016/j.poly.2020.114844.
  10. ^ "4,4'-Methylenedianiline". NIOSH Pocket Guide on Chemical Hazards.
  11. ^ Kopelman H, Robertson MH, Sanders PG, Ash I (February 1966). "The Epping jaundice". British Medical Journal. 1 (5486): 514–6. doi:10.1136/bmj.1.5486.514. PMC 1843808. PMID 5902696.
Allikas: https://en.wikipedia.org/wiki/Methylenedianiline
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