Quinacridone Quinone

Quinacridones are not the only industrially significant products. The list may be extended to include the derivative mentioned in Section 3.2.1.4, the linear trans-quinacridone quinone. There are two other synthetic pathways besides the hydroquinone method. The older method involves cyclization of the 2,5-bis-(2 -carboxyanilino-)-l, 4-benzoquinone 63 with concentrated sulfuric acid or polyphos-phoric acid at 150 to 200°C. The starting material 63 is obtained through condensation of 1,4-benzoquinone with anthranilic acid  

A more recent synthesis proceeds via 2,5-diarylamino-3,6-dicarbethoxy-l, 4-hy-droquinone 65, which is obtained by reducing 2,5-diarylamino-3,6-dicarbethoxy-1,4-benzoquinone 64 with sodium hydrogensulfite or sodium in ethanol  

The hydroquinone 65 is cyclized in an organic solvent at 230 to 270°C to yield 6,13-dihydroxy-quinacridone 66. Oxidation with suitable agents (such as nitrobenzene, chromic acid, nitric acid) provides the linear trans-quinacridone quinone (62)  

Linear trans-quinacridones exhibit multiple crystal modifications. This phenomenon is reflected in the different reflection angles which are observed in the X-ray diffraction spectra of the pigment powders. This effect may be exemplified by describing the polymorphous phases of unsubstituted quinacridone. 

The (3-lorm is obtained by dissolving crude quinacridone in any one of a variety of solvents (such as concentrated sulfuric acid/toluene or methylated sulfuric acid), followed by precipitation with water. The same end is achieved by dissolving the product in polyphosphoric acid, followed by rapid precipitation with ethanol at 45°C. The (3-product, however, is not pure and usually contains some a-crystal modification as well. 

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Subsequent ring closure of the 2,5-diarylamino-1,4-benzoquinone-3,6-dicarboxylic acid (61) is performed in concentrated sulfuric acid (or with thionyl chloride/ni-trobenzene) to afford the linear trans-quinacridone quinone 62. 

P.O.48 mixed crystal phase with quinacridone quinone unsubstituted quinacridone maroon (golden yellow) 1... 

Other mixed phases are made from quinacridone quinone with unsubstituted quinacridone or 4,11-dichloroquinacridone as a second component. 

Quinacridone quinone itself (Sec. 3.2.1.6) is a tinctorially relatively weak yellow compound with poor lightfastness. Formation of mixed crystal phases with other quinacridones (Sec. 3.2.2) as well as treatment with various metal salts [25] leads to an improvement of light- and weatherfastness. Oxidation of dihy-droquinacridone with less than molar amounts of chromate affords a quin-acridone/quinacridone quinone mixed phase which offers an interesting shade of gold. 

P.R.206 is a mixed crystal type and consists of unsubstituted quinacridone and quinacridone quinone. The ratio between the two components as well as the crystal modification is not yet known. P.R.206 affords a very dull, yellowish shade of red, referred to as maroon. The pigment is considerably weaker than perylene pigments. All commercially available types of P.R.206 are more or less transparent and are used mostly in metallic finishes for automobiles, to which they lend reddish shades of copper. The pigment is often found to be difficult to disperse. The finishes frequently exhibit rheological problems, especially at high pigment concentration. 

The exact physical properties of P.O.49, i.e., mainly the crystal modification of this quinacridone/quinacridone quinone pigment remain to be published. P.O.49, like P.R.209, is a specialty product for metallic shades. It is used to produce shades of gold in finishes, which are considerably more yellowish than those of P.O.48. 

Today a maroon containing about 60% quinacridone and 40% quinacridonequinone and a gold containing about 75% quinacridone-quinone are sold commercially. Solid solutions can also be prepared between variously substituted linear trans-quinacridones. and a scarlet containing a mixture of approximately 60% quinacridone and 40% 4,11-dichloroquinacridone (an orange) is also on the market. 

Quinacridone quinone High activity Colored (brown) Fujiyama, 19%... 

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