XIV

Thioindigo

Names
Preferred IUPAC name ※-3H,3′H-※-3,3′-dione
Other names DyStar, "C."I. Vat Red 41, "C."I. 73 300
Identifiers
CAS Number	522-75-8
3D model (JSmol)	Interactive image
ChemSpider	4527286
ECHA InfoCard	100.007.580
PubChem CID	3033973
UNII	V993X7635Y
CompTox Dashboard (EPA)	DTXSID8060169
InChI InChI=1S/C16H8O2S2/c17-13-9-5-1-3-7-11(9)19-15(13)16-14(18)10-6-2-4-8-12(10)20-16/h1-8H/b16-15+ Key: JOUDBUYBGJYFFP-FOCLMDBBSA-N InChI=1/C16H8O2S2/c17-13-9-5-1-3-7-11(9)19-15(13)16-14(18)10-6-2-4-8-12(10)20-16/h1-8H/b16-15+ Key: JOUDBUYBGJYFFP-FOCLMDBBBL
SMILES O=C3c4ccccc4S/C3=C2/Sc1ccccc1C2=O
Properties
Chemical formula	C16H8O2S2
Molar mass	296.36 g·mol
Appearance	Red solid
Melting point	280 °C (536 °F; 553 K)
Solubility in water	Insoluble
Solubility in ethanol, xylene	Soluble
Except where otherwise noted, data are given for materials in their standard state (at 25 °C ※, 100 kPa). N verify (what is  ?) 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 to create a shade of pink.

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. The related compound 4,7,4',7'-tetrachlorothioindigo, also a commercially important dye (Pigment Red 88), can be, prepared by chlorination of thioindigo.

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