Toluidine

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There are three isomers of toluidine, which are organic compounds discovered and named by James Sheridan Muspratt and August Wilhelm von Hofmann in 1845. [1] These isomers are o-toluidine, m-toluidine, and p-toluidine, with the prefixed letter abbreviating, respectively, ortho; meta; and para. All three are aryl amines whose chemical structures are similar to aniline except that a methyl group is substituted onto the benzene ring. The difference between these three isomers is the position where the methyl group (–CH3) is bonded to the ring relative to the amino functional group (–NH2); see illustration of the chemical structures below. [2]

Contents

Toluidine isomers
Methyl positionorthometapara
Common name o-toluidine m-toluidinep-toluidine
Other nameso-methylanilinem-methylanilinep-methylaniline
Chemical name 2-methylaniline3-methylaniline4-methylaniline
Chemical formula C7H9N
Molecular mass 107.17 g/mol
Glass transition temperature 189 K [3] 187 K [4] Glass not formed [3]
Melting point −23 °C−30 °C43 °C
Boiling point 199–200 °C203–204 °C200 °C
Density 1.00 g/cm30.98 g/cm31.05 g/cm3
Magnetic susceptibility76.0 × 10−6 cm3/mol74.6 × 10−6 cm3/mol72.1 × 10−6 cm3/mol
CAS number [95-53-4][108-44-1][106-49-0]
SMILES Cc1ccccc1NCc1cccc(N)c1Cc1ccc(N)cc1
O-Toluidin.svg M-Toluidin.svg P-Toluidin.svg
Disclaimer and references

The chemical properties of the toluidines are quite similar to those of aniline, and toluidines have properties in common with other aromatic amines. Due to the amino group bonded to the aromatic ring, the toluidines are weakly basic. The toluidines are poorly soluble in pure water but dissolve well in acidic water due to formation of ammonium salts, as usual for organic amines. ortho- and meta-toluidines are viscous liquids, but para-toluidine is a flaky solid. This difference is related to the fact that the p-toluidine molecules are more symmetrical. p-Toluidine can be obtained from reduction of p-nitrotoluene. p-Toluidine reacts with formaldehyde to form Tröger's base.

Uses and occurrence

The ortho isomer is produced on the largest scale. Its primary application is as a precursor to the pesticides metolachlor and acetochlor. [2] The other toluidine isomers are used in the production of dyes such as Allura Red AC (Red 40, E129) and azorubine (carmoisine, E122). They are a component of accelerators for cyanoacrylate glues.

In some patients o-toluidine is a metabolite of prilocaine, which may cause methemoglobinemia. This is then treated with methylene blue.

References

  1. ↑ Muspratt, James Sheridan; Hofmann, Augustus William (September 1845). "On toluidine, a new organic base". The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science. 27 (179): 178–194. doi:10.1080/14786444508645253. ISSN   1941-5966.
  2. 1 2 Bowers, Joseph S. "Toluidines". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. doi:10.1002/14356007.a27_159. ISBN   978-3-527-30673-2.
  3. 1 2 Pratesi, G.; Bartolini, P.; Senatra, D.; Ricci, M.; Righini, R.; Barocchi, F.; Torre, R. (2003). "Experimental studies of the ortho-toluidine glass transition". Physical Review E. 67 (2): 021505. Bibcode:2003PhRvE..67b1505P. doi:10.1103/PhysRevE.67.021505. PMID   12636682.{{cite journal}}: CS1 maint: article number as page number (link)
  4. ↑ Alba-Simionesco, C.; Fan, J.; Angell, C. A. (1999). "Thermodynamic aspects of the glass transition phenomenon. II. Molecular liquids with variable interactions". The Journal of Chemical Physics. 110 (11): 5262. Bibcode:1999JChPh.110.5262A. doi:10.1063/1.478800.
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