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Ullmann Reaction |
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Ullmann reaction [′əl·mən rē‚ak·shən]
(organic chemistry) A variation of the Fittig synthesis, using copper powder instead of sodium. Ullmann Reaction a method of obtaining binuclear and polynuclear aromatic compounds by heating aryl halides (ArX, where X = CI, Br, I) at 100°-360°C with powdered copper. One example of the Ullmann reaction is the synthesis of diphenyl from iodobenzene: 2C6H5I + Cu → C6H5 - C6H5 + Cul2 Iodine derivatives enter into the Ullmann reaction more readily. An increased yield is made possible by the activation of copper, for example, with iodine in acetone, and by the application of a solvent—dimethylformamide. It is assumed that the Ullmann reaction proceeds according to a free-radical mechanism. Discovered by F. Ullmann in 1896, the reaction is used, for example, in the manufacture of vat dyes. Want to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit the webmaster's page for free fun content. |
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