Azalein (tar dye)
Azalein is a red tar dye that is rarely used today and consists of rosaniline nitric acid .
history
In 1856, Perkin concluded from the fact that quinine (a chemical compound consisting of carbon, hydrogen, nitrogen and oxygen) must be able to be produced from coal tar distillates (consisting of carbon, hydrogen and nitrogen) under oxidative conditions (oxygen supply).
Little was known about the structure of organic compounds at the time. Only the elemental composition was known, based on the elemental analysis developed by Justus von Liebig (see also the five-ball apparatus ). At that time nothing was known about the exact structures, especially about the structure of aromatic compounds ( aromatics , recognized by Friedrich August Kekulé von Stradonitz , 1861).
In his attempts to synthesize quinine by oxidizing a mixture of aniline and toluidine with potassium dichromate , Perkin obtained a dye which colored silk purple and which he called aniline purple . This was later given the name Mauvein (named after the flower color of the mallow ). Aniline purple / mauvein was the first synthetically produced dye.
In 1858, August Wilhelm von Hofmann , German chemist, and almost simultaneously François-Emmanuel Verguin , French chemist, discovered aniline red through the action of arsenic acid aniline. Aniline red was named after the American ornamental plant fuchsia fuchsin .
In 1859, Jean Gerber-Keller & Sohn (F-Mulhouse) developed a new process for the production of aniline red in which they used mercury nitrate as an oxidizing agent (so-called azalein method ). They wanted to market the dye under the trade name Azalein ; it was superior to fuchsin in terms of its coloring power, purity and price. However, a patent filed in France was rejected due to the existing property rights for fuchsin. Since all products made from coal tar had a similar structure, the French patent blocked further research in France. In 1859, Switzerland was, alongside Turkey, one of the few countries without regulated protection of inventions. For this reason, production was started in Basel .
Manufacturing
Azalein is formed by the action of oxidizing agents in the heat on aniline contaminated with toluidine. The nitrate is obtained using the Jean Gerber-Keller & Sohn method . Formally, the reaction can be interpreted as an electrophilic substitution of aniline by p -aminobenzaldehyde and subsequent elimination of water:
Depending on the degree of contamination of the aniline with toluidine, more or less alkylated compounds are obtained. It is therefore not possible to give an exact structural formula .
meaning
Azalein was an economically important dye at the end of the 19th century. Overall, however, the patent dispute over aniline dyes, in particular fuchsia and azalein, had a significant influence on the creation of national invention protection rights. Since these protective rights led to national monopolies (Fuchsin patent), which led to excessive prices nationally, but also caused production facilities to migrate to other countries, the "invention" of azalein also had political significance.
Individual evidence
- ^ Springer-Verlag Berlin Heidelberg New York; Globalization Strategies, The Novartis Way ISBN 3-540-41629-3 .