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The Wallach rearrangement is an organic reaction and a rearrangement reaction converting an aromatic azoxy compound with sulfuric acid to an azo compound with one arene ring substituted by an hydroxyl group in the aromatic para position.
Additional recommended knowledge
60% to 100% sulfuric acid is required.
The reaction mechanism for this reaction is not known with great precision despite experimental evidence:
A mechanism not inconsistent with these findings is depicted below:
In the first part of the reaction two equivalents of acid tease the oxygen atom away from the azoxy group. The resulting dicationic intermediate 3 with an unusual R-N+:::N+-R motif in this scheme has been observed by proton NMR in a system of fluoroantimonic acid and azoxybenzene at -50°C . In the second part of the reaction the HSO4- anion is a nucleophile in a nucleophilic aromatic substitution to 5 followed by hydrolysis to 6.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Wallach_rearrangement". A list of authors is available in Wikipedia.|