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The Chemical Educator

ISSN: 1430-4171 (electronic version)

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Abstract Volume 12 Issue 5 (2007) pp 307-313

Conversion of Urea to Hydrazine: Hofmann Reaction or Favorskii Analogue? Exploring Reaction Mechanism Through Isotopic Labeling Studies

Paul S. Francis* and Kieran F. Lim

School of Life and Environmental Sciences, Deakin University, Geelong, Victoria 3217, Australia,
Received November 11, 2006. Accepted February 24, 2007.

Published online: 10 September 2007

Abstract. The power of isotopic substitution for the elucidation of a reaction mechanism is illustrated with reactions named after Hofmann and Favorskii. These reactions have important roles in synthetic chemistry; therefore, a wide range of experiments involving isotopic labeling or kinetic isotope effects were employed to establish their mechanistic pathways. The concepts introduced by these investigations are drawn together with an isotopic labeling study of the oxidation of urea with hypohalites. The two mechanisms proposed for this reaction have been described as a Hofmann rearrangement and a nitrogen analogue of the Favorskii rearrangement.

Key Words: In the Classroom; organic chemistry; physical chemistry; isotopes; kinetics; mechanisms of reactions

(*) Corresponding author. (E-mail:

Article in PDF format (180 KB) HTML format

Supporting Materials:

Examples of the Hofmann, Favorskii and related rearrangements have been included as supporting material (243 KB).

Issue date: October 1, 2007

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