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CAS number 522-75-8 YesY
PubChem 3033973
ChemSpider 4527286
Jmol-3D images Image 1
Molecular formula C16H8O2S2
Molar mass 296.36 g mol−1
Appearance Red solid
Melting point 280 °C (536 °F; 553 K)
Solubility in water Insoluble
Solubility in ethanol, xylene Soluble[vague]
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Thioindigo is an organosulfur compound that is used to dye polyester fabric. A synthetic dye, thioindigo is related to the plant-derived dye indigo, replacing two NH groups with two sulfur atoms.

Thioindigo is generated by the alkylation of the sulfur in thiosalicylic acid with chloroacetic acid. The resulting thioether cyclizes to 2-hydroxythianaphthene, which is easily converted to thioindigo.[1] The related compound 4,7,4',7'-tetrachlorothioindigo, also a commercially important dye, can be prepared by chlorination of thioindigo.


  1. ^ Elmar Steingruber "Indigo and Indigo Colorants" in Ullmann's Encyclopedia of Industrial Chemistry, 2004, Wiley-VCH, Weinheim. doi: 10.1002/14356007.a14_149.pub2