Toluidine

{{short description|Group of chemical compounds: aryl amines}} There are three isomers of '''toluidine''', which are organic compounds discovered and named by James Sheridan Muspratt and August Wilhelm von Hofmann in 1845.<ref>{{Cite journal |last1=Muspratt |first1=James Sheridan |last2=Hofmann |first2=Augustus William |date=September 1845 |title=On toluidine, a new organic base |url=https://books.google.com/books?id=P7PN-PlMrlQC&pg=PA178 |journal=The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science |language=en |volume=27 |issue=179 |pages=178–194 |doi=10.1080/14786444508645253 |issn=1941-5966}}</ref> 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.<ref name=Ullmann>{{Ullmann|first=Joseph S. |last=Bowers |title=Toluidines |doi=10.1002/14356007.a27_159}}</ref>

<!-- Submit {{:subst:chembox_simple_organic}} to get this template or go to :Template:Chembox_simple_organic. --> {| class="wikitable" border="1" style="text-align:center; background:#ffffff;" ! colspan="4" style="background:#ccccff;" | 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 | colspan="3" | C₇H₉N |- | Molecular mass | colspan="3" | 107.17 g/mol |- | Glass transition temperature | 189 K<ref name=r1>{{cite journal|last1=Pratesi|first1=G.|last2=Bartolini|first2=P.|last3=Senatra|first3=D.|last4=Ricci|first4=M.|last5=Righini|first5=R.|last6=Barocchi|first6=F.|last7=Torre|first7=R.|title=Experimental studies of the ''ortho''-toluidine glass transition|journal=Physical Review E|volume=67|year=2003|doi=10.1103/PhysRevE.67.021505|issue=2|article-number=021505 |pmid=12636682 |bibcode=2003PhRvE..67b1505P }}</ref> | 187 K<ref>{{cite journal|last1=Alba-Simionesco|first1=C.|last2=Fan|first2=J.|last3=Angell|first3=C. A.|title=Thermodynamic aspects of the glass transition phenomenon. II. Molecular liquids with variable interactions|journal=The Journal of Chemical Physics|volume=110|page=5262|year=1999|doi=10.1063/1.478800|issue=11|bibcode=1999JChPh.110.5262A }}</ref> | ''Glass not formed''<ref name=r1/> |- | 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 |- | | 90px | 90px | 45px |- | colspan=4 style="background:#ccccff;" | <small>Disclaimer and references</small> |}

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.<ref name=Ullmann/> 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== {{reflist}}

==External links== * [http://www.osha.gov/dts/chemicalsampling/data/CH_272505.html MSDS] * [https://www.cdc.gov/niosh/npg/npgd0622.html ''o''-Toluidine], [https://www.cdc.gov/niosh/npg/npgd0623.html ''m''-Toluidine], [https://www.cdc.gov/niosh/npg/npgd0624.html ''p''-Toluidine] CDC – NIOSH Pocket to Chemical Hazards

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Category:Anilines Category:Toluenes