There are threeisomers oftoluidine, which areorganic compounds discovered and named byJames Sheridan Muspratt andAugust Wilhelm von Hofmann in 1845.[1] These isomers areo-toluidine,m-toluidine, andp-toluidine, with the prefixed letter abbreviating, respectively,ortho;meta; andpara. All three arearyl amines whosechemical structures are similar toaniline except that amethyl 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 theaminofunctional group (–NH2); see illustration of the chemical structures below.[2]
| Toluidine isomers | |||
|---|---|---|---|
| Methyl position | ortho | meta | para |
| Common name | o-toluidine | m-toluidine | p-toluidine |
| Other names | o-methylaniline | m-methylaniline | p-methylaniline |
| Chemical name | 2-methylaniline | 3-methylaniline | 4-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 °C | 43 °C |
| Boiling point | 199–200 °C | 203–204 °C | 200 °C |
| Density | 1.00 g/cm3 | 0.98 g/cm3 | 1.05 g/cm3 |
| Magnetic susceptibility | 76.0 × 10−6 cm3/mol | 74.6 × 10−6 cm3/mol | 72.1 × 10−6 cm3/mol |
| CAS number | [95-53-4] | [108-44-1] | [106-49-0] |
| SMILES | Cc1ccccc1N | Cc1cccc(N)c1 | Cc1ccc(N)cc1 |
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| Disclaimer and references | |||
The chemical properties of the toluidines are quite similar to those ofaniline, and toluidines have properties in common with otheraromatic amines. Due to the amino group bonded to the aromatic ring, the toluidines areweakly basic. The toluidines are poorlysoluble in purewater but dissolve well inacidic water due to formation ofammonium salts, as usual for organic amines.ortho- andmeta-toluidines are viscousliquids, butpara-toluidine is a flakysolid. This difference is related to the fact that thep-toluidinemolecules are more symmetrical.p-Toluidine can be obtained fromreduction ofp-nitrotoluene.p-Toluidine reacts withformaldehyde to formTröger's base.
Theortho isomer is produced on the largest scale. Its primary application is as a precursor to the pesticidesmetolachlor andacetochlor.[2] The other toluidine isomers are used in the production ofdyes such asAllura Red AC (Red 40, E129) andazorubine (carmoisine, E122). They are a component of accelerators forcyanoacrylate glues.
In some patientso-toluidine is a metabolite ofprilocaine, which may causemethemoglobinemia. This is then treated withmethylene blue.
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