Thioindigo

Structural formula
General
Surname	Thioindigo
other names	CI Vat Red 41 CI 73300
Molecular formula	C 16 H 8 O 2 S 2
Brief description	red to purple powder
External identifiers / databases
CAS number 522-75-8 EC number 208-336-1 ECHA InfoCard 100.007.580 PubChem 5378456 Wikidata Q411535
properties
Molar mass	296.37 g mol −1
Physical state	firmly
Melting point	280 ° C
solubility	almost insoluble in water, soluble in xylene with yellow in ethanol with brown-red color
safety instructions
GHS labeling of hazardous substances no GHS pictograms H and P phrases H: no H-phrases P: no P-phrases
Toxicological data	4170 mg kg −1 ( LD 50 ,  rat ,  oral )
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Thioindigo is a chemical compound from the group of organosulfur compounds that is used as a dye. It is similar to the better known indigo , with its two imine groups (NH) being replaced by sulfur .

Extraction and presentation

Thioindigo was discovered by Paul Friedlaender at the beginning of the 20th century and was originally obtained from indigo by the addition of sulfur (hence the Greek prefix “thio”). It is a quinacridone pigment . Today a number of production processes are known for the compound and its chlorine derivatives, usually by oxidation of the corresponding 3-hydroxythionaphthenes. S-alkylation of thiosalicylic acid with chloroacetic acid is also possible . The resulting thioether cyclizes to 2-hydroxythionaphthene , which dimerizes to thioinigo.

properties

Thioindigo is a red to purple powder. It occurs in two different crystal structures. Thioindigo II has a monoclinic crystal structure with the space group P2 ₁ / n, while Thioindigo I has the space group P2 ₁ / c. In addition to the normal trans form, the isomeric cis form (isothioindigo) also occurs. In a benzene solution there is an equilibrium between the two forms.

use

Indanthrene brilliant rose R, a derivative of thioindigo.

Thioindigo is used as a purple dye. After the discovery of the quinacridone pigment group around 1935, DuPont established them on the market as synthetic pigments in the 1960s. The related compound 4,7,4 ', 7'-tetrachlorothioindigo, a likewise commercially important dye, can be obtained by chlorinating thioindigo. The related compound Indanthrenbrillantrosa R (CI 73360) is a red thioindio pigment. It is used in cosmetic products such as toothpaste or lipsticks, while the German Cosmetics Ordinance bans it in hair dyes.

There are other derivatives with residues attached to the rings which have very good light and weather fastness as well as migration and solvent fastness (this depends very much on the position of the substituents). The hues of these thioindigo pigments range from red-violet to brown.

Individual evidence

1. ↑ ^{a b c d e} Entry on thioindigo at TCI Europe, accessed on November 1, 2016.
2. ↑ ^{a b} Brockhaus ABC Chemie , VEB FA Brockhaus Verlag Leipzig 1965, pp 1409-1410.
3. ↑ Patent EP0056867 : Process for the preparation of 4,4'-7,7'-tetrachloro thioindigo. Published on August 4, 1982 , inventor: Helmut Hoch, Heinrich Hiller. ‌
4. ↑ Elmar Steingruber: Indigo and Indigo Colorants . In: Ullmann's Encyclopedia of Industrial Chemistry . Wiley-VCH, Weinheim 2000, ISBN 978-3-527-30673-2 , doi : 10.1002 / 14356007.a14_149.pub2 .
5. ^ W. Haase-Wessel, M. Ohmasa, P. Süsse: Thioindigo: Crystal structural data for modification II . In: Natural Sciences . tape 64 , no. 8 , 1977, pp. 435-435 , doi : 10.1007 / BF00508700 .
6. ↑ Thioindigo (Kremer Pigments)  ( page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.  
7. ↑ W. Müller (Ed.): Handbuch der Farbenchemie. Basics, technology, applications . Ecomed Publishing Company; 3. Supplementary delivery 2003; ISBN 3-609-72700-4 ; P. 17 (Chapter 19.1).
8. ↑ synthetic organic colorants ( Memento from March 19, 2013 in the Internet Archive ) (PDF; 625 kB)