Abstract

Azine, oxazine, and thiazine dyes were among the earliest of synthetic dyes. The names are derived from the 6-member heterocyclic ring system present in all dyes of these classes: 1,4-diazine, 1,4-oxazine, and 1,4-thiazine. Azine, oxazine, and thiazine dyes were historically more important than they are at present. However, at least one example of each, introduced more than 100 years ago, is still offered commercially today. Azo and anthraquinone dyes have largely displaced them in commercial application. Azo dyes offer better fastness and broader shade ranges at more economical prices. Azine dyes are used extensively as biological stains. Colors are mostly yellow to red. Oxazine dyes have seen use as laser dyes and titration indicators. Oxazine dyes containing sulfonic acid groups are claimed to be suitable for dyeing leather in brown shades. Methylene Blue CI Basic Blue 9(CI 52015), is the classic thiazine dye still in use today. Thiazine is not important in dyes as such, but it is a part of some reactive dyes.