Triarylmethane dye

Triarylmethane dyes are synthetic organic compounds containing triphenylmethane backbones. As dyes, these compounds are intensely colored. Many of these dyes undergo reactions in response to acid and base, and thus serve as pH indicators.^[1]

As a consequence of their structure, the Friedel-Crafts alkylation reaction is a popular method to prepare many of these compounds:

Families

Triarylmethane dyes can be grouped into families according to the nature of the substituents on the aryl groups. In some cases, the anions associated with the cationic dyes (say crystal violet) vary even though the name of the dye does not. Often it is shown as chloride.

Methyl violet dyes

Methyl violet dyes have dimethylamino groups at the p-positions of two aryl groups, since they are prepared from Mischler's ketone.

• Methyl violet dyes
• 

  Methyl violet 2B

• 

  Methyl violet 6B

• 

  Methyl violet 10B

Fuchsine dyes

Fuchsine dyes have amine (NH₂ or NHMe) functional groups at the p-positions of each aryl group.

• Fuchsine dyes
• 

  Pararosaniline

• 

  Fuchsine (hydrochloride salt)

• 

  New fuchsine (cation)

• 

  Fuchsine acid

Phenol dyes

Phenol dyes have hydroxyl groups at the p positions of each aryl group.

• Phenol dyes
• 

  Phenol red

• 

  Chlorophenol red

• 

  Cresol red

Malachite green dyes

Malachite green dyes are related to the methyl violet dyes, except that they contain one phenyl (C₆H₅) group.

• Malachite green dyes
• 

  Malachite green

• 

  Brilliant Green (dye)

Bridged arenes

Where two of the aryl groups are bridged by a heteroatom, these triarylmethane compounds may be further categorized into acridines (nitrogen-bridged), xanthenes (oxygen-bridged), and thioxanthenes (sulfur-bridged).

References

Wikimedia Commons has media related to Triarylmethane dye.