Editing Indigo dye (section)

===Synthetic development===
[[File:Indigoproduktion BASF 1890.JPG|thumb|Production of Indigo dye in a [[BASF]] plant (1890)]]
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 a second synthesis in 1880 (from [[2-nitrobenzaldehyde]]). (It was not until 1883 that Baeyer finally determined the structure of indigo.<ref>Adolf Baeyer (1883) [https://gallica.bnf.fr/ark:/12148/bpt6k90697p/f512.image.langEN "Ueber die Verbindungen der Indigogruppe"] [On the compounds of the indigo group], ''Berichte der Deutschen chemischen Gesellschaft zu Berlin'', '''16''' : 2188-2204; see especially p. 2204.</ref>) 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<ref name="history.evonik.com">{{cite web |url=https://history.evonik.com/sites/geschichte/en/personalities/pfleger-johannes/pages/default.aspx |title=Johannes Pfleger - Das Evonik Geschichtsportal - Die Geschichte von Evonik Industries |website=history.evonik.com |access-date=7 June 2020 |archive-date=1 August 2020 |archive-url=https://web.archive.org/web/20200801202949/https://history.evonik.com/sites/geschichte/en/personalities/pfleger-johannes/pages/default.aspx |url-status=dead}}</ref> and [[:de:Karl Heumann|Karl Heumann]] eventually came up with industrial mass production synthesis.<ref name="ingenious.org.uk">{{cite web |url=http://www.ingenious.org.uk/site.asp?s=RM&Param=1&SubParam=1&Content=1&ArticleID=%7BCBDF1082-9F5C-498F-A769-B33A7DA83B30%7D&ArticleID2=%7B3C4444FC-FC4D-4498-B0B4-8B8A47C5BA76%7D&MenuLinkID=%7BA54FA022-17E2-483C-B937-DEC8B8964C33%7D |title=The Synthesis of Indigo |access-date=2015-01-05 |archive-url=https://web.archive.org/web/20160304084155/http://www.ingenious.org.uk/site.asp?s=RM&Param=1&SubParam=1&Content=1&ArticleID=%7BCBDF1082-9F5C-498F-A769-B33A7DA83B30%7D&ArticleID2=%7B3C4444FC-FC4D-4498-B0B4-8B8A47C5BA76%7D&MenuLinkID=%7BA54FA022-17E2-483C-B937-DEC8B8964C33%7D |archive-date=2016-03-04 |url-status=dead}}</ref>

The synthesis of N-(2-carboxyphenyl)glycine from 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.<ref>{{cite journal |title=Chemists go green to make better blue jeans |journal=Nature |year=2018 |volume=553 |issue=7687 |page=128 |doi=10.1038/d41586-018-00103-8 |bibcode=2018Natur.553..128. |doi-access=free}}</ref>