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56-632: Hydantoin was first isolated in 1861 by Adolf von Baeyer in the course of his study of uric acid . He obtained it by hydrogenation of allantoin , hence the name. Friedrich Urech synthesized 5-methylhydantoin in 1873 from alanine sulfate and potassium cyanate in what is now known as the Urech hydantoin synthesis . The method is very similar to the modern route using alkyl and arylcyanates. The 5,5-dimethyl compound can also be obtained from acetone cyanohydrin (also discovered by Urech: see cyanohydrin reaction ) and ammonium carbonate . This reaction type

112-766: A chunk of indigo worth two Thalers for his first dye experiments. When a schoolboy, his chemistry teacher at the Friedrich Wilhelm Gymnasium appointed him as his assistant. After graduating from secondary school in 1853, he entered the Berlin University to study physics and mathematics. A stint in the Prussian army interrupted his study until 1856, when he returned to academia at the University of Heidelberg , intending to study chemistry under Robert Bunsen . After an argument with

168-511: A dye (particularly for silk ) for centuries. The dye was also known to ancient civilizations in Mesopotamia , Egypt , Britain , Mesoamerica , Peru , Iran , and West Africa . Indigo was also cultivated in India, which was also the earliest major center for its production and processing. The Indigofera tinctoria species was domesticated in India. Indigo, used as a dye, made its way to

224-772: A major export crop, indigo supported plantation slavery there. In the May and June 1755 issues of The Gentleman's Magazine , there appeared a detailed account of the cultivation of indigo, accompanied by drawings of necessary equipment and a prospective budget for starting such an operation, authored by South Carolina planter Charles Woodmason . It later appeared as a book. By 1775, indigo production in South Carolina exceeded 1,222,000 pounds. When Benjamin Franklin sailed to France in November 1776 to enlist France's support for

280-436: A professor at the University of Strasbourg in 1871. In 1875, he succeeded Justus von Liebig as Chemistry Professor at the University of Munich . Baeyer's chief achievements include the synthesis and description of the plant dye indigo , the discovery of the phthalein dyes, and the investigation of polyacetylenes , oxonium salts , nitroso compounds (1869) and uric acid derivatives (1860 and onwards) (including

336-620: A rare commodity throughout the Middle Ages. A chemically identical dye derived from the woad plant ( Isatis tinctoria ) was used instead. In the late 15th century, the Portuguese explorer Vasco da Gama discovered a sea route to India. This led to the establishment of direct trade with India, the Spice Islands , China, and Japan. Importers could now avoid the heavy duties imposed by Persian , Levantine , and Greek middlemen and

392-451: A second synthesis in 1880 (from 2-nitrobenzaldehyde ). (It was not until 1883 that Baeyer finally determined the structure of indigo. ) The synthesis of indigo remained impractical, so the search for alternative starting materials at Badische Anilin- und Soda-Fabrik (BASF) and Hoechst continued. Johannes Pfleger and Karl Heumann eventually came up with industrial mass production synthesis. The synthesis of N-(2-carboxyphenyl)glycine from

448-504: A vat and soaking hydrolyzes the indican, releasing β- D - glucose and indoxyl . The indoxyl dimerizes in the mixture, and after 12–15 hours of fermentation yields the yellow, water-soluble leucoindigo . Subsequent exposure to air forms the blue, water-insoluble indigo dye. The dye precipitates from the fermented leaf solution upon oxidation, but may also be precipitated when mixed with a strong base such as lye . The solids are filtered, pressed into cakes, dried, and powdered. The powder

504-492: A vat was decorated with the techniques of shibori ( tie-dye ), kasuri , katazome , and tsutsugaki . Examples of clothing and banners dyed with these techniques can be seen in the works of Hokusai and other artists. Two different methods for the direct application of indigo were developed in England in the 18th century and remained in use well into the 19th century. The first method, known as 'pencil blue' because it

560-402: A young age while she was giving birth to his sister Adelaide. Although his birth name was Johann Friedrich Wilhelm Adolf Baeyer, he was known simply as Adolf throughout most of his life. The poet Adelbert von Chamisso and the astronomer Friedrich Wilhelm Bessel were his godparents. On his 50th birthday he was raised to the hereditary nobility by King Ludwig II of Bavaria , conferring on him

616-472: Is a dark blue crystalline powder that sublimes at 390–392 °C (734–738 °F). It is insoluble in water, alcohol , or ether , but soluble in DMSO , chloroform , nitrobenzene , and concentrated sulfuric acid . The chemical formula of indigo is C 16 H 10 N 2 O 2 . The molecule absorbs light in the orange part of the spectrum ( λ max =613 nm). The compound owes its deep color to

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672-601: Is also the Von Baeyer nomenclature in structural chemistry and Baeyer strain theory (which granted him the Nobel prize) of alicyclic compounds . In 2009 von Baeyer lunar crater was named after him. In 1868, Baeyer married Adelheid (Lida) Bendemann, the daughter of a family friend, and together the couple had three children: Eugenie, Hans, and Otto  [ de ] . He died on 20 August 1917 in Starnberg at

728-636: Is also used as a food colorant, and is listed in the United States as FD&C Blue No. 2. A variety of plants have provided indigo throughout history, but most natural indigo was obtained from those in the genus Indigofera , which are native to the tropics, notably the Indian Subcontinent. The primary commercial indigo species in Asia was true indigo ( Indigofera tinctoria , also known as I. sumatrana ). A common alternative used in

784-524: Is also used in mixtures with the above. A high proportion of cytosine and thymine bases in DNA are oxidized to hydantoins over time after the death of an organism. Such modifications block DNA polymerases and thus prevents PCR from working. Such damage is a problem when dealing with ancient DNA samples. Adolf von Baeyer Johann Friedrich Wilhelm Adolf von Baeyer ( German: [ˈaːdɔlf fɔn ˈbaɪɐ] ; 31 October 1835 – 20 August 1917)

840-464: Is called the Bucherer–Bergs reaction . Hydantoin can also be synthesized either by heating allantoin with hydroiodic acid or by "heating bromacetyl urea with alcoholic ammonia". The cyclic structure of hydantoins was confirmed by Dorothy Hahn 1913. Of practical importance, hydantoins are obtained by condensation of a cyanohydrin with ammonium carbonate . Another useful route, which follows

896-529: Is credited to Pfleger in 1901. In this process, N -phenylglycine is treated with a molten mixture of sodium hydroxide , potassium hydroxide , and sodamide . This highly sensitive melt produces indoxyl , which is subsequently oxidized in air to form indigo. Variations of this method are still in use today. An alternative and also viable route to indigo is credited to Heumann in 1897. It involves heating N -(2-carboxyphenyl)glycine to 200 °C (392 °F) in an inert atmosphere with sodium hydroxide. The process

952-655: Is easier than the Pfleger method, but the precursors are more expensive. Indoxyl-2-carboxylic acid is generated. This material readily decarboxylates to give indoxyl, which oxidizes in air to form indigo. The preparation of indigo dye is practised in college laboratory classes according to the original Baeyer-Drewsen route. The oldest known fabric dyed indigo, dated to 6,000 years ago, was discovered in Huaca Prieta , Peru. Many Asian countries, such as India , China, Japan, and Southeast Asian nations have used indigo as

1008-670: Is not soluble in water. To be dissolved, it must undergo a chemical change ( reduction ). Reduction converts indigo into "white indigo" ( leuco -indigo). When a submerged fabric is removed from the dyebath, the white indigo quickly combines with oxygen in the air and reverts to the insoluble, intensely colored indigo. When it first became widely available in Europe in the 16th century, European dyers and printers struggled with indigo because of this distinctive property. It also required several chemical manipulations, some involving toxic materials, and presented many opportunities to injure workers. In

1064-681: Is produced industrially via the hydantoin obtained from methional . Methylation of hydantoin yields a variety of derivatives. Dimethylhydantoin (DMH) may refer to any dimethyl derivative of hydantoin, but especially 5,5-dimethylhydantoin . Some N -halogenated derivatives of hydantoin are used as chlorinating or brominating agents in disinfectant /sanitizer or biocide products. The three major N -halogenated derivatives are dichlorodimethylhydantoin (DCDMH), bromochlorodimethylhydantoin (BCDMH), and dibromodimethylhydantoin (DBDMH). A mixed ethyl-methyl analogue, 1,3-dichloro-5-ethyl-5-methylimidazolidine-2,4-dione ( bromochloroethylmethylhydantoin ),

1120-528: Is secreted by a common Mediterranean snail. It was highly prized in antiquity. In 1909, its structure was shown to be 6,6'-dibromoindigo (red). 6-bromoindigo (purple) is a component as well. It has never been produced on a commercial basis. The related Ciba blue (5,7,5',7'-tetrabromoindigo) is, however, of commercial value. Indigo and its derivatives featuring intra- and intermolecular hydrogen bonding have very low solubility in organic solvents. They can be made soluble using transient protecting groups such as

1176-804: Is then mixed with various other substances to produce different shades of blue and purple. Natural sources of indigo also include mollusks: the Murex genus of sea snails produces a mixture of indigo and 6,6'-dibromoindigo (red), which together produce a range of purple hues known as Tyrian purple . Light exposure during part of the dyeing process can convert the dibromoindigo into indigo, resulting in blue hues known as royal blue, hyacinth purple, or tekhelet . Given its economic importance, indigo has been prepared by many methods. The Baeyer–Drewsen indigo synthesis dates back to 1882. It involves an aldol condensation of o-nitrobenzaldehyde with acetone, followed by cyclization and oxidative dimerization to indigo. This route

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1232-479: Is used as a muscle relaxant to treat malignant hyperthermia , neuroleptic malignant syndrome , spasticity , and ecstasy intoxication. Ropitoin is an example of an antiarrhythmic hydantoin. The hydantoin derivative Imiprothrin is a pyrethroid insecticide . Iprodione is a popular fungicide containing the hydantoin group. Hydrolysis of hydantoins affords amino acids: Hydantoin itself reacts with hot, dilute hydrochloric acid to give glycine . Methionine

1288-646: The American Revolutionary War , 35 barrels of indigo were on board the Reprisal , the sale of which would help fund the war effort. In colonial North America, three commercially important species are found: the native I. caroliniana , and the introduced I. tinctoria and I. suffruticosa . In 1865 the German chemist Adolf von Baeyer began working on the synthesis of indigo. He described his first synthesis of indigo in 1878 (from isatin ) and

1344-458: The Edo period . This was due to a growing textiles industry, and because commoners had been banned from wearing silk, leading to the increasing cultivation of cotton, and consequently indigo – one of the few substances that could dye it. In North America, indigo was introduced into colonial South Carolina by Eliza Lucas , where it became the colony's second-most important cash crop (after rice). As

1400-532: The Greeks and the Romans , where it was valued as a luxury product. In Mesopotamia, a neo-Babylonian cuneiform tablet of the seventh century BC gives a recipe for the dyeing of wool, where lapis -colored wool ( uqnatu ) is produced by repeated immersion and airing of the cloth. Indigo was most probably imported from India. The Romans used indigo as a pigment for painting and for medicinal and cosmetic purposes. It

1456-566: The Indigo revolt in 1859. The Bengali play Nil Darpan by Indian playwright Dinabandhu Mitra was a fictionalized retelling of the revolt. The demand for indigo in the 19th century is indicated by the fact that in 1897, 7,000 km (2,700 sq mi) were dedicated to the cultivation of indican-producing plants, mainly in India . By comparison, the country of Luxembourg is 2,586 km (998 sq mi). In Europe, indigo remained

1512-580: The Mandinka of Mali particularly well known for their expertise. Among the Hausa male dyers, working at communal dye pits was the basis of the wealth of the ancient city of Kano , and they can still be seen plying their trade today at the same pits. The Tuareg are sometimes called the "Blue People" because the indigo pigment in the cloth of their traditional robes and turbans stained their skin dark blue. In Japan, indigo became especially important during

1568-487: The Virgin Islands . However, France and Germany outlawed imported indigo in the 16th century to protect the local woad dye industry. In central Europe, indigo resist dyeing is a centuries-old skill that has received UNESCO Intangible Cultural Heritage of Humanity recognition. Newton used "indigo" to describe one of the two new primary colors he added to the five he had originally named, in his revised account of

1624-564: The tBOC group , which suppresses intermolecular bonding. Heating of the tBOC indigo results in efficient thermal deprotection and regeneration of the parent H-bonded pigment. Treatment with sulfuric acid converts indigo into a blue-green derivative called indigo carmine (sulfonated indigo). It became available in the mid-18th century. It is used as a colorant for food, pharmaceuticals, and cosmetics. Indigo and some of its derivatives are known to be ambipolar organic semiconductors when deposited as thin films by vacuum evaporation. Indigo has

1680-402: The "von" distinction. Baeyer became interested in science early, performing experiments on plant nutrition at his paternal grandfather's Müggelsheim farm as a boy. In Berlin he began chemical experimentation at the age of nine. Three years later, he synthesized a previously unknown chemical compound -double carbonate of copper and sodium. On his 13th birthday, he initiated his lifework, buying

1736-519: The 19th century, English poet William Wordsworth referred to the plight of indigo dye workers of his hometown of Cockermouth in his autobiographical poem The Prelude . Speaking of their dire working conditions and the empathy that he felt for them, he wrote: Doubtless, I should have then made common cause With some who perished; haply perished too A poor mistaken and bewildered offering Unknown to those bare souls of miller blue A pre-industrial process for production of indigo white, used in Europe,

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1792-525: The China blue method. Since 2004, freeze-dried indigo, or instant indigo, has become available. In this method, the indigo has already been reduced, and then freeze-dried into a crystal. The crystals are added to warm water to create the dye pot. As in a standard indigo dye pot, care has to be taken to avoid mixing in oxygen. Freeze-dried indigo is simple to use, and the crystals can be stored indefinitely as long as they are not exposed to moisture. Indigo dye

1848-474: The age of 81. Indigo dye Indigo dye is an organic compound with a distinctive blue color . Indigo is a natural dye extracted from the leaves of some plants of the Indigofera genus, in particular Indigofera tinctoria . Dye-bearing Indigofera plants were commonly grown and used throughout the world, particularly in Asia, with the production of indigo dyestuff economically important due to

1904-490: The chemical industry, through his work on organic dyes and hydroaromatic compounds", and he continued in full active work as one of the best-known teachers in the world of organic chemistry up to within a year of his death. The Adolf von Baeyer Medal  [ de ] has been awarded annually since 1911. His name is reflected in various "name reactions" as the Baeyer–Villiger oxidation and Baeyer's reagent . There

1960-409: The conjugation of the double bonds , i.e. the double bonds within the molecule are adjacent and the molecule is planar. In indigo white, the conjugation is interrupted because the molecule is non-planar. The benzene rings in indigo can be modified to give a variety of related dyestuffs. Thioindigo , where the two NH groups are replaced by S atoms, is deep red. Tyrian purple is a dull purple dye that

2016-531: The discovery of barbituric acid (1864), the parent compound of the barbiturates ). He was the first to propose the correct formula for indole in 1869, after publishing the first synthesis three years earlier. His contributions to theoretical chemistry include the 'strain' ( Spannung ) theory of triple bonds and strain theory in small carbon rings. In 1871 he discovered the synthesis of phenolphthalein by condensation of phthalic anhydride with two equivalents of phenol under acidic conditions (hence

2072-420: The easy to obtain aniline provided a new and economically attractive route. BASF developed a commercially feasible manufacturing process that was in use by 1897, at which time 19,000 tons of indigo were being produced from plant sources. This had dropped to 1,000 tons by 1914 and continued to contract. By 2011, 50,000 tons of synthetic indigo were being produced worldwide. Indigo is a challenging dye because it

2128-421: The historical rarity of other blue dyestuffs. Most indigo dye produced today is synthetic , constituting around 80,000 tonnes each year, as of 2023. It is most commonly associated with the production of denim cloth and blue jeans , where its properties allow for effects such as stone washing and acid washing to be applied quickly. The primary use for indigo is as a dye for cotton yarn, mainly used in

2184-468: The insoluble form of indigo onto the fabric. The indigo was then reduced in a sequence of baths of iron(II) sulfate , with air oxidation between each immersion. The China blue process could make sharp designs, but it could not produce the dark hues possible with the pencil blue method. Around 1880, the 'glucose process' was developed. It finally enabled the direct printing of indigo onto fabric and could produce inexpensive dark indigo prints unattainable with

2240-574: The lengthy and dangerous land routes which had previously been used. Consequently, the importation and use of indigo in Europe rose significantly. Much European indigo from Asia arrived through ports in Portugal, the Netherlands, and England. Many indigo plantations were established by European powers in tropical climates. Spain imported the dye from its colonies in Central and South America, and it

2296-487: The name). That same year he was the first to obtain synthetic fluorescein , a fluorophore pigment which is similar to naturally occurring pyoverdin that is synthesised by microorganisms (e.g., by some fluorescent strains of Pseudomonas ). Baeyer named his finding "resorcinphthalein" as he had synthesised it from phthalic anhydride and resorcinol . The term fluorescein would not start to be used until 1878. In 1872 he experimented with phenol and formaldehyde ;

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2352-408: The production of denim cloth suitable for blue jeans; on average, a pair of blue jeans requires 3 grams (0.11 oz) to 12 grams (0.42 oz) of dye. Smaller quantities are used in the dyeing of wool and silk. Indigo carmine , also known as indigo, is an indigo derivative which is also used as a colorant. About 20,000 tonnes are produced annually, again mainly for the production of blue jeans. It

2408-622: The rainbow in Lectiones Opticae of 1675. Because of its high value as a trading commodity, indigo was often referred to as blue gold. Throughout West Africa, Indigo was the foundation of centuries-old textile traditions. From the Tuareg nomads of the Sahara to Cameroon , clothes dyed with indigo signified wealth. Women dyed the cloth in most areas, with the Yoruba of Nigeria and

2464-527: The relatively colder subtropical locations such as Japan's Ryukyu Islands and Taiwan is Strobilanthes cusia . Until the introduction of Indigofera species from the south, Persicaria tinctoria (dyer's knotweed) was the most important blue dyestuff in East Asia; however, the crop produced less dyestuff than the average crop of indigo, and was quickly surpassed in favour of the more economical Indigofera tinctoria plant. In Central and South America,

2520-426: The relatively low concentrations of indigo in these plants make them difficult to work with, with the color more easily tainted by other dye substances also present in these plants, typically leading to a greenish tinge. The precursor to indigo is indican , a colorless, water-soluble derivative of the amino acid tryptophan , and Indigofera leaves contain as much as 0.2–0.8% of this compound. Pressing cut leaves into

2576-535: The renowned chemist he changed his mentor to August Kekulé . He continued to collaborate with Kekulé even after he returned to Berlin in 1858 for the completion of his doctorate on arsenic methyl chloride, or cacodylic chloride . After completing his doctorate, he followed Kekulé to the University of Ghent , when Kekulé became professor there. He became a lecturer at the Gewerbeinstitut Berlin  [ de ] (Royal Trade Academy) in 1860 and

2632-726: The resinous product was a precursor for Leo Baekeland 's later commercialization of Bakelite . In 1881 the Royal Society of London awarded Baeyer the Davy Medal for his work with indigo. He was elected a Foreign Honorary Member of the American Academy of Arts and Sciences in 1884. In 1905 he was awarded the Nobel Prize in Chemistry "in recognition of his services in the advancement of organic chemistry and

2688-458: The species grown is Indigofera suffruticosa , also known as anil , and in India, an important species was Indigofera arrecta , Natal indigo. In Europe, Isatis tinctoria , commonly known as woad, was used for dyeing fabrics blue, containing the same dyeing compounds as indigo, also referred to as indigo. Several plants contain indigo, which, when exposed to an oxidizing source such as atmospheric oxygen, reacts to produce indigo dye; however,

2744-533: The time of his birth and he was raised in the Lutheran religion. His mother was the daughter of Julius Eduard Hitzig and a member of the originally Jewish Itzig family , and had converted to Christianity before marrying his father, who was of non-Jewish German descent. Baeyer had four sisters: Clara (born 1826) Emma (born 1831), Johanna (Jeanette) (born 1839), Adelaide (died 1843) and two brothers: Georg (born 1829) and Edward (born 1832). Baeyer lost his mother at

2800-428: The work of Urech, involves the condensation of amino acids with cyanates and isocyanates: The hydantoin group can be found in several medicinally important compounds. In pharmaceuticals, hydantoin derivatives form a class of anticonvulsants ; phenytoin and fosphenytoin both contain hydantoin moieties and are both used as anticonvulsants in the treatment of seizure disorders. The hydantoin derivative dantrolene

2856-778: Was a German chemist who synthesised indigo and developed a nomenclature for cyclic compounds (that was subsequently extended and adopted as part of the IUPAC organic nomenclature ). He was ennobled in the Kingdom of Bavaria in 1885 and was the 1905 recipient of the Nobel Prize in Chemistry . Baeyer was born in Berlin as the son of the noted geodesist and captain of the Royal Prussian Army Johann Jacob Baeyer and his wife Eugenie Baeyer née Hitzig (1807–1843). Both his parents were Lutherans at

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2912-729: Was a luxury item imported to the Mediterranean from India by Arab merchants. India was a primary supplier of indigo to Europe as early as the Greco-Roman era. The association of India with indigo is reflected in the Greek word for the dye, indikón ( Ἰνδικόν , Indian). The Romans latinized the term to indicum , which passed into Italian dialect and eventually into English as the word indigo. In Bengal indigo cultivators revolted against exploitative working conditions created by European merchants and planters in what became known as

2968-515: Was a major crop in Haiti and Jamaica, with much or all of the labor performed by enslaved Africans and African Americans. In the Spanish colonial era, intensive production of indigo for the world market in the region of modern El Salvador entailed such unhealthy conditions that the local indigenous population, forced to labor in pestilential conditions, was decimated. Indigo plantations also thrived in

3024-534: Was highly useful for obtaining indigo and many of its derivatives on the laboratory scale, but proved impractical for industrial-scale synthesis. Johannes Pfleger and Karl Heumann  [ de ] eventually came up with industrial mass production synthesis from aniline by using mercury as a catalyst. The method was discovered by an accident by Karl Heumann in Zurich which involved a broken thermometer. The first commercially practical route of producing indigo

3080-428: Was most often applied by pencil or brush, could be used to achieve dark hues. Arsenic trisulfide and a thickener were added to the indigo vat. The arsenic compound delayed the oxidation of the indigo long enough to paint the dye onto fabrics. The second method was known as 'China blue' due to its resemblance to Chinese blue-and-white porcelain. Instead of using an indigo solution directly, the process involved printing

3136-476: Was to dissolve the indigo in stale urine, which contains ammonia. A more convenient reductive agent is zinc. Another pre-industrial method, used in Japan, was to dissolve the indigo in a heated vat in which a culture of thermophilic , anaerobic bacteria was maintained. Some species of such bacteria generate hydrogen as a metabolic product, which convert insoluble indigo into soluble indigo white. Cloth dyed in such

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