Indigo is a blue dye, which has been used all over the world since ancient times. It is said that the blue linen cloth that wrapped the mummy (the body of the preserved person) in Egypt thousands of years ago was dyed with indigo. The English word indigo comes from the Greek word indikon, which is the blue dye of Indians. All the blue clothes worn by ordinary people in our country have been dyed with it.
Indigo is a herb several feet high. Its stems and leaves contain a glucoside (18). After fermentation and hydrolysis, not only glucose but also white indophenol aqueous solution is produced. Soak the white cloth in this white solution and put it in the air for oxidation, that is, produce water-insoluble blue precipitated indigo, which firmly adheres to textile fibers and is resistant to sunlight, water washing and heating. This principle is used in batik, which is still popular among Buyi, Miao and Yao people in China. First, draw a picture on white cloth with wax liquid, then soak it in white indophenol aqueous solution, oxidize it in the air, and then boil it for dewaxing, that is, make a bright blue and white pattern. This began in the Han Dynasty and prevailed in the Tang Dynasty.
1826- 184 1 year, European chemists degraded natural indigo, and found that it melted with potassium hydroxide (KOH) at low temperature to obtain o-aminobenzoic acid, while aniline was obtained at high temperature, and then it was oxidized with nitric acid or chromium trioxide to obtain indigo.
1865, the german chemist Johann Friedrich William adolf Bayer (1835- 19 17) tried to convert indigo into indigo by reduction, but he got indole:
Bayer became interested in indigo as early as 13 years old. This year, he bought a large piece of indigo dye from the drugstore, and after returning home, he did experiments according to the instructions in the chemistry book, trying to turn indigo into indigo. 1865 became a lecturer at Berlin technical school and began to study indigo. He failed many times, but he never gave up.
Eight years later 1878, Bayer artificially produced indigo from phenylacetic acid, and then converted it into indigo, which can be considered as synthetic indigo. However, due to too many steps and low yield, it is not suitable for industrial production.
Subsequently, Bayer successfully synthesized indigo from o-nitrocinnamic acid and o-nitropropionic acid, and obtained a patent on1March 9 1880, and published a scientific report on1August 8 of the same year. 1882, he synthesized indigo from o-nitrotoluene, but both of them failed to realize industrialization because of their high cost.
In the unremitting process of synthesizing indigo, Bayer gradually deepened its understanding of the molecular chemical structure of indigo, and proposed its structural formula in 1883. Bayer thus won the 1905 Nobel Prize in Chemistry.
Industrialized production of indigo until 1890, Karl Heumann, a professor at Swiss Technical School (1850- 1893) put forward a plan. He proposed that it was made of phenylglycine o- carboxylic acid, and then two indophenol molecules combined to form indigo:
The problem is how to prepare a large amount of phenylglycine o-carboxylic acid to meet the needs of industrial production. Neumann used naphthalene extracted from coal tar as the basic raw material, oxidized it into phthalic acid with concentrated sulfuric acid, and then treated it with ammonia water, potassium hypochlorite and chloroacetic acid to obtain phenylglycine o-carboxylic acid.
In the process of industrialization, the reaction of naphthalene oxidation with concentrated sulfuric acid is slow, and Batischer aniline and soda ash plant in Germany spent100000 pounds on experimental research, but failed to achieve results. Until 1897, an accidental event had a miraculous effect. A worker accidentally broke the mercury thermometer and fell into the reactor. Naphthalene began to boil and turned into phthalic acid. Obviously, the mercury in the mercury thermometer reacts with sulfuric acid to generate mercury sulfate, which plays a catalytic role.
However, the industrial production of indigo was not put into production immediately, because a large amount of concentrated sulfuric acid, caustic soda and chlorine gas were needed in the production process. It was not until the beginning of the 20th century, after the industrial rise of concentrated sulfuric acid production and electrolytic salt solution production of caustic soda and chlorine, that indigo was produced by contact method. 1914-1918 after the first world war, many countries carried out industrial production of indigo, and put forward some other production schemes, such as taking aniline as raw material, condensing with chloroacetic acid in the presence of sodium hydroxide and ferrous sulfate, then adding sodium amino to sodium hydroxide and potassium hydroxide, melting under pressure, and then.
Synthetic indigo is the greatest achievement in the history of synthetic dye industry, which fully shows the strength of science and industry.
Another great achievement in the history of synthetic dye industry is the synthesis of alizarin.
Alizarin is also an ancient dye, which exists in the roots of madder. Madder is a climbing herb, which grows in the grass in Shan Ye. Both the Yangtze River and the Yellow River are distributed in China, and also widely grow along the Mediterranean coast and the Near East. Its roots contain a glycoside, which, after fermentation and hydrolysis, produces various colored substances, the most important of which is alizarin, which comes from Arabic and means madder root. There is also purplish red pigment, which was introduced by Robiquet (1780-1840) and Colin (1784- 1865) in 1827. Alizarin can be dyed red, pink and lavender with different mordants. The Egyptians used alizarin staining as early as 1500 BC. 1870 After the Franco-Prussian War broke out, thousands of French soldiers wore uniform red military pants, because the climate and soil in France were very suitable for planting madder. 16~ 17 century, madder was widely planted in some European countries, but it was always difficult to meet the market demand, so chemists looked for ways to synthesize alizarin artificially.
1868, Graber (184 1- 1927) and Lieberman (1842- 1965438) worked in Bayer Laboratories. Anthracene This is a compound composed of three benzene rings. After further study, they speculated that alizarin was dihydroxy anthraquinone. On this basis, the two of them tried to synthesize this dye. They designed such a synthetic route: using anthracene extracted from coal tar as raw material, anthracene was oxidized to anthraquinone, then two bromine atoms were introduced into anthraquinone to generate dibromoanthraquinone, and then hydrolyzed, hoping to finally get alizarin. But the synthesis experiment was unsuccessful. 1869, they melted dibromoanthraquinone with strong alkali * * *, and as a result, a synthetic alizarin exactly the same as natural alizarin was obtained:
Synthetic alizarin looks purer than natural alizarin, which can be said to be unique. Graber and Lieberman applied for a patent for this and got approval. However, the synthetic route of this patent is too complicated, the cost is too high, and a lot of expensive bromine is consumed, so it is difficult to melt on an industrial scale. Or an engineer at Batischer Aniline Soda Factory in Germany? After many experiments, Carlo finally invented the sulfonation process. Anthraquinone was first heated with concentrated sulfuric acid at a high enough temperature to obtain water-soluble sulfonic acid derivatives, and then melted with strong alkali to obtain alizarin, with a yield of 90%.
Zhao kuanghua. General history of chemistry. Beijing: Higher Education Press, 1990.
Carlo, Graber and Lieberman applied for a patent for this synthesis method again, but it was not approved by the Patent Office, which thought it was no different from the first edition patent. So they thought of going to Britain to apply for a patent. On June 25th, 1869, the British Patent Office approved their patent application.
Coincidentally, the next day, the British chemist and entrepreneur Parkin also registered almost the same patent for alizarin synthesis. Later, Parkin reached a cross-licensing trade with Batischer aniline and soda ash plant.
Marx evaluated the significance of synthesizing alizarin. In Das Kapital, he said: "The method of extracting alizarin and alizarin red dye from coal tar, using the existing equipment for producing coal tar dye, can get the results that took several years before in a few weeks. It takes a year for madder to grow, and then it will take several years for madder roots to grow and mature before they can be made into dyes. "