Toluidine

O, m, p

O, m, p

The toluidines ( as aminotoluenes ( Aminotoluene ) or methyl anilines known ) are a group of substances in the chemical industry and are aromatic compounds having a methyl group (- CH3) and an amino group (-NH2) as a substituent on the benzene ring. Different arrangement of the substituents (ortho, meta or para), three constitutional isomers arise with the formula C7H9N. They are primarily used as precursors in the manufacture of dyes and pigments of importance.

Representation

The Toluidine be from nitrotoluene ( from toluene by nitration available ) prepared by reduction. The reduction may be carried out on the one hand of iron, hydrochloric acid and acetic acid ( Bechamp reduction). Today, the catalytic hydrogenation with Raney nickel is predominant. Lower aliphatic alcohols ( methanol, ethanol, n-propanol or iso- propanol) are herein often used as the solvent. The hydrogenation is typically at pressures from 3 bar to 20 bar instead of H2 pressure (so-called Niederdruckhydrierung ) or at 20 to 50 bar (so-called Mitteldruckhydrierung ).

Properties

The Toluidine have almost the same high boiling points differ significantly, however, in their melting points. The p -toluidine, due to its symmetry, the highest melting point and is a solid.

The Toluidine are weak bases, their ( pKa values) are in the same order as aniline ( 4.603 ).

The vapor pressure functions arise after Antoine corresponding log10 (P) = A- ( B / ( T C )) ( P in bar, T in K) as follows:

Reactions

The toluidines form stable salts with strong organic and inorganic acids.

The most important reactions are the

• Acetylation
• Alkylation
• Aralkylation
• Arylation and
• Diazotization

The chemical behavior of toluidine is also ( as in the aniline) by the aromatic ring and the amino group determined.

Use

The toluidines had earlier almost entirely as intermediates for the preparation of dyes and pigments very important. Ortho -toluidine is not released from textiles or leather that prolonged periods of time with the human skin directly in contact are (Appendix 1 of the Consumer Goods Ordinance ) after reductive cleavage of azo groups. Meanwhile, some of the herbicides containing them can be produced. o-and p -toluidine are important starting materials for the preparation of nitrided Chlortoluidinen and toluidines. These are used, in addition to the Toluidinsulfonsäuren for the manufacture of pharmaceuticals, dyes and pigments.

About diazotization ( and subsequent " boiling down ") can be obtained from the toludines the cresols.