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PRIMULINE, a dye-stuff containing the thiazole ring system conjointly with a benzene ring. The primulines are to be considered as derivatives of dehydrothiotoluidine (aminobenzenyltoluylmercaptan), which is obtained when para-tolui-
S\
CH „/\/
•CBH4.NH,(p)
\/\N/
Primuline.
dine is heated with sulphur for eighteen hours at 18o–xgo C. and then for a further six hours at 200–2200 C. (P. Jacobson, Ber., 1889, 22, p. 333; L. Gattermann, ibid. p. 1084). Dehydrothiotoluidine is not itself a dye-stuff, but if the heating be carried out at a higher temperature in the presence of more sulphur, then a base is formed, which gives primuline yellow on sulphonation (A. G. Green, Journ. Soc. Chem. Ind., 1888, r, p. 194). Primuline-yellow is a mixture of sodium salts and probably contains in the molecule at least three thiazole rings
in combination. It is a substantive cotton dye of rather fugitive shade, but can be diazotized on the fibre and then developed with other components, so yielding a series of ingrain colours.
Thioflavine T is obtained by the methylation of dehydrothiotoluidine with methyl alcohol in the presence of hydrochloric acid [German Patent 51738 (1888)]. Thioflavine S results from the methylation of dehydrothiotoluidine sulphonic acid. This sulphonic acid on oxidation with bleaching powder or with lead peroxide, in alkaline solution yields chloramine yellow, which dyes cotton a beautiful yellow.