Alizarin cyanine R

Alizarin cyanine R is an anthraquinone dye and belongs to the mordant dyes

History

Alizarin cyanine R was discovered by R. E. Schmidt in 1891.

Representation

Alizarin cyanine R can be obtained by oxidation of alizarin Bordeaux with manganese dioxide, analogous to the oxidation of alizarin to purpurin.
Another route involves Chinalizarin, which is treated with manganese dioxide in sulfuric acid, followed by oxidation of the resulting quinone and subsequent reduction (chemistry) with sulfurous acid.
A further possibility is the oxidation of anthrapurpurin with Oleum.

Use

This dye yields a violet aluminum lacquer and a blue chrome lacquer.

Differentiation from C.I. Mordant Blue 32

The Colour Index lists C.I. Mordant Blue 32 under the constitution number C.I. 58605 and describes it as 1,2,4,5,6,8-hexahydroxy-9,10-anthraquinone, which was discovered by R. Bohn in 1891.

	C.I. Mordant Blue 32
Name	1,2,4,5,6,8-Hexahydroxy-9,10-anthracenedione
Structural formula
CAS number	61169-36-6
PubChem	80762
ChemSpider
Wikidata	Q27104411
Sum formula	C₁₄H₈O₈
Molar mass	304.022 g·mol⁻¹

SciFinder lists C.I. Mordant Blue 32 under the CAS number 6373-24-6, in which five hydroxy groups are located at the 1, 2, 4, 5, and 8 positions of the anthraquinone, while the sixth hydroxy group is variably assigned to either the 6 or 7 position.
According to the Colour Index, the respective technical products contain the alternate isomer as an impurity.