Ullmann Reaction

Ullmann reaction

[′əl·mən rē‚ak·shən]

(organic chemistry)

A variation of the Fittig synthesis, using copper powder instead of sodium.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

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.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.