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{{short description|Class of dye}}
'''Triarylmethane dyes''' are synthetic [[organic compound]]s 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 indicator]]s.<ref>{{Ullmann's | last1 = Gessner | first1 = Thomas | last2 = Mayer | first2 = Udo | title = Triarylmethane and Diarylmethane Dyes | year = 2000 | doi = 10.1002/14356007.a27_179}}</ref>
'''Triarylmethane dyes''' are synthetic [[organic compound]]s containing [[triphenylmethane]] backbones. As [[dye]]s, these compounds are intensely colored. They are produced industrially as dyes.<ref name=Ull>{{Ullmann's | last1 = Gessner | first1 = Thomas | last2 = Mayer | first2 = Udo | title = Triarylmethane and Diarylmethane Dyes | year = 2000 | doi = 10.1002/14356007.a27_179}}</ref>

:[[File:Bromocresol_green_ionic_equilibrium.png|500px|Bromocresol green reacts with acids and bases to give differently colored compounds]]

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

:[[File:ThymolphthaleinSynthesis.png|350px|Friedel-Crafts synthesis of thymolphthalein]]


==Families==
==Families==
Some triarylmethane dyes can be grouped into families of dyes with very similar structures. In some cases, the [[anion]]s associated with the cationic dyes (say crystal violet) vary even though the name of the dye does not.
Triarylmethane dyes can be grouped into families according to the nature of the substituents on the aryl groups. In some cases, the [[anion]]s 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===
Methyl violet dyes have dimethylamino groups at the ''p''-positions of two aryl groups.
<gallery>
<gallery caption="Methyl violet dyes" widths="180px" heights="120px" perrow="3">
Image:Methyl Violet 2B.png|[[Methyl violet]] 2B
Image:Methyl Violet 6B.png|[[Methyl violet]] 6B
Image:Methyl Violet 2B.svg|[[Methyl violet 2B]]
Image:Methyl Violet 10B.png|[[Crystal violet|Methyl violet 10B]]
Image:Methyl Violet 6B.svg|[[Methyl violet 6B]]
Image:Kristallviolett.svg|[[Crystal violet|Methyl violet 10B]]
</gallery>
</gallery>


===Fuchsine dyes===
===Fuchsine dyes===
Fuchsine dyes have amine functional groups at the ''p''-positions of each phenyl group.
Fuchsine dyes have primary or secondary amines (NH<sub>2</sub> or NHMe) functional groups at the ''p''-positions of each aryl group.
<gallery caption="Fuchsine dyes" widths="180px" heights="120px" perrow="4">
<gallery>
File:Pararosaniline.png|[[Pararosaniline]]
File:Pararosaniline.png|[[Pararosaniline]]
File:Rosaniline_hydrochloride.png|[[Fuchsine]] (hydrochloride salt)
File:Rosaniline hydrochloride.svg|[[Fuchsine]] (hydrochloride salt)
File:New_fuchsine.png|[[New fuchsine]] (cation)
Neofuchsin.svg|[[New fuchsine]] (As chloride)
File:Fuchsine_acid.png|[[Fuchsine acid]]
Fuchsine acid vector.svg|[[Fuchsine acid]]
</gallery>
</gallery>


===Phenol dyes===
===Phenol dyes===
Phenol dyes have hydroxyl groups at the ''p'' positions of each phenyl group.
Phenol dyes have hydroxyl groups at the ''p'' positions of at least two aryl groups.

<gallery>
<gallery caption="Phenol dyes" widths="180px" heights="120px" perrow="3">
File:Phenolphthalein-low-pH-2D-skeletal.svg|[[Phenolphthalein]]
File:Phenol-red-zwitterionic-form-2D-skeletal.png|[[Phenol red]]
File:Phenol-red-zwitterionic-form-2D-skeletal.png|[[Phenol red]]
File:Chlorophenol red.png|[[Chlorophenol red]]
File:Chlorophenol red.png|[[Chlorophenol red]]
File:Structure of cresol red.png|[[Cresol red]]
File:Cresol Red.svg|[[Cresol red]]
File:Bromocresol purple.svg|[[Bromocresol purple]]
File:Bromocresol green.svg|[[Bromocresol green]]
</gallery>
</gallery>


===Malachite green dyes===
===Malachite green dyes===
Malachite green dyes are related to the methyl violet dyes, except that they contain one phenyl (C<sub>6</sub>H<sub>5</sub>) group.
<gallery>
<gallery caption="Malachite green dyes" widths="180px" heights="120px" perrow="3">
Image:Malachite green structure.svg |[[Malachite green]]
Image:Malachite green structure.svg |[[Malachite green]]
Image:Structure of the dye brilliant green.png|[[Brilliant Green (dye)]]
Image:Structure of the dye brilliant green.png|[[Brilliant green (dye)]]
Image:Brilliant Blue FCF(2).svg|[[Brilliant blue FCF]], a common food colorant
</gallery>

===Victoria blue dyes===
Victoria blue dyes are related to the methyl violet dyes, except they contain one naphthylamino group. Variation is found is dimethylamine vs diethylamino substituents on the phenyl rings and variations of the secondary amine on the naphthyl group.
<gallery caption="Victoria blue dyes" widths="180px" heights="120px" perrow="3">
File:Victoria blue B with charge.svg|[[Victoria blue B]]
File:Victoria blue FBR revised.svg |[[Victoria blue FBR]]
File:Victoria blue BO.svg|[[Victoria blue BO]]
File:Victoria pure blue FGA revised.svg|[[Victoria blue FGA]]
File:Victoria blue 4 R revised.svg|[[Victoria blue 4 R]]
File:Victoria blue R revised.svg|[[Victoria blue R]]
</gallery>

===Xanthene dyes===
{{see also|fluoran}}
Xanthene dyes feature a [[xanthene]] core. They are not widely used as textiles, but for other applications.
<gallery caption="Xanthene dyes" widths="180px" heights="120px" perrow="3">
File:EosinB.png|[[Eosin B]]
File:EosinY.png|[[Eosin Y]]
File:rhodamine B.svg|[[Rhodamine B]]
File:Rhodamine 123.svg|[[Rhodamine 123]]
File:Fluorescein 2.svg |[[Fluorescein]]
</gallery>
</gallery>


==Bridged arenes==
==Bridged arenes==
Where two of the aryl groups are bridged by a heteroatom, these triarylmethane compounds may be further categorized into [[acridine]]s (nitrogen-bridged), [[xanthene]]s (oxygen-bridged), and [[thioxanthene]]s (sulfur-bridged).
Where two of the aryl groups are bridged by a [[heteroatom]], these triarylmethane compounds may be further categorized into [[acridine]]s (nitrogen-bridged), [[xanthene]]s (oxygen-bridged), and [[thioxanthene]]s (sulfur-bridged).

==Synthesis==
The amine-containing dyes are often prepared from [[Michler's ketone]] or its diethylamino analogue. In this way, the third aryl group is readily differentiated. The [[Friedel–Crafts alkylation]] reaction is a popular method to prepare many of the phenolic derivatives:
:[[File:ThymolphthaleinSynthesis.png|350px|Friedel–Crafts synthesis of thymolphthalein]]

==Applications==
In addition to their dominant use as dyes, many of these dyes react reversibly with acid and base, and thus serve as [[pH indicator]]s.<ref name=Ull/>
:[[File:Bromocresol green ionic equilibrium.png|500px|Bromocresol green reacts with acids and bases to give differently colored compounds]]

==See also==
*[[Zelyonka attack]]
*[[Phthalein dye]]


==References==
==References==
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{{reflist}}
{{reflist}}


[[Category:Triarylmethane dyes| ]]

[[Category:Triarylmethane dyes|*]]

Latest revision as of 16:57, 7 December 2024

Triarylmethane dyes are synthetic organic compounds containing triphenylmethane backbones. As dyes, these compounds are intensely colored. They are produced industrially as dyes.[1]

Families

[edit]

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

[edit]

Methyl violet dyes have dimethylamino groups at the p-positions of two aryl groups.

Fuchsine dyes

[edit]

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

Phenol dyes

[edit]

Phenol dyes have hydroxyl groups at the p positions of at least two aryl groups.

Malachite green dyes

[edit]

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

Victoria blue dyes

[edit]

Victoria blue dyes are related to the methyl violet dyes, except they contain one naphthylamino group. Variation is found is dimethylamine vs diethylamino substituents on the phenyl rings and variations of the secondary amine on the naphthyl group.

Xanthene dyes

[edit]

Xanthene dyes feature a xanthene core. They are not widely used as textiles, but for other applications.

Bridged arenes

[edit]

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).

Synthesis

[edit]

The amine-containing dyes are often prepared from Michler's ketone or its diethylamino analogue. In this way, the third aryl group is readily differentiated. The Friedel–Crafts alkylation reaction is a popular method to prepare many of the phenolic derivatives:

Friedel–Crafts synthesis of thymolphthalein

Applications

[edit]

In addition to their dominant use as dyes, many of these dyes react reversibly with acid and base, and thus serve as pH indicators.[1]

Bromocresol green reacts with acids and bases to give differently colored compounds

See also

[edit]

References

[edit]
  1. ^ a b Gessner, Thomas; Mayer, Udo (2000). "Triarylmethane and Diarylmethane Dyes". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a27_179. ISBN 978-3527306732.