Thioindigo
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 to create a shade of pink.
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| Names | |
|---|---|
| Preferred IUPAC name
 [2(2′)E]-3H,3′H-[2,2′-Bi-1-benzothiophenylidene]-3,3′-dione  | |
| Other names
 DyStar, C.I. Vat Red 41, C.I. 73 300  | |
| Identifiers | |
3D model (JSmol)  | 
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| ChemSpider | |
| ECHA InfoCard | 100.007.580 | 
PubChem CID  | 
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| UNII | |
CompTox Dashboard (EPA)  | 
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| Properties | |
| C16H8O2S2 | |
| Molar mass | 296.36 g·mol−1 | 
| Appearance | Red solid | 
| Melting point | 280 °C (536 °F; 553 K) | 
| Insoluble | |
| Solubility in ethanol, xylene | Soluble | 
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). 
Infobox references  | |
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.
References
    
- Elmar Steingruber "Indigo and Indigo Colorants" in Ullmann's Encyclopedia of Industrial Chemistry, 2004, Wiley-VCH, Weinheim. doi:10.1002/14356007.a14_149.pub2
 
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