Reactivity in Chemistry

Electrophilic Rearrangement

ER5.  Wolff Rearrangement

The Wolff rearrangement is the conversion of a diazoketone to a ketene, usually under photolytic conditions.

The loss of dinitrogen from the diazonium compound would result in an electron-deficient carbene.  Like a carbocation, the carbene would be susceptible to a 1,2-shift.  If accompanied by π-donation from the carbene to the carbonyl, a ketene would result.

As with other rearrangements, the 1,2-shift could occur at the same time as the loss of the dinitrogen.

Ketenes are not terribly stable.  In the presence of nucleophilic solvents such as water or alcohol, the ketene easily undergoes nucleophilic addition.  Addition of water would result in a carboxylic acid.

The mechanism of that addition involves keto-enol tautomerism.

Problem ER5.1.

Predict the products of the following Wolff rearrangements.

This site is written and maintained by Chris P. Schaller, Ph.D., College of Saint Benedict / Saint John's University (with contributions from other authors as noted).  It is freely available for educational use.

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Structure & Reactivity in Organic, Biological and Inorganic Chemistry by Chris Schaller is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License

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This material is based upon work supported by the National Science Foundation under Grant No. 1043566.

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