World Library  
Flag as Inappropriate
Email this Article

Wöhler synthesis

Article Id: WHEBN0002749404
Reproduction Date:

Title: Wöhler synthesis  
Author: World Heritage Encyclopedia
Language: English
Subject: Friedrich Wöhler, Organic reactions, Ammonia, Urea
Publisher: World Heritage Encyclopedia

Wöhler synthesis

The Wöhler synthesis is the conversion of salt appears only as an (unstable) intermediate. Wöhler demonstrated the reaction in his original publication with different sets of reactants: a combination of cyanic acid and ammonia, a combination of silver cyanate and ammonium chloride, a combination of lead cyanate and ammonia and finally from a combination of mercury cyanate and cyanatic ammonia (which is again cyanic acid with ammonia).

The reaction can be demonstrated by starting with solutions of potassium cyanate and ammonium chloride which are mixed, heated and cooled again. An additional proof of the chemical transformation is obtained by adding a solution of oxalic acid which forms urea oxalate as a white precipitate.

Alternatively the reaction can be carried out with lead cyanate and ammonia. The actual reaction taking place is a double displacement reaction to form ammonium cyanate:

\mathrm{Pb(NCO)_2 + 2NH_3 + 2H_2O \rightarrow Pb(OH)_2 + 2NH_4(NCO)}

Ammonium cyanate decomposes to ammonia and cyanic acid which in turn react to produce urea in a nucleophilic addition followed by tautomeric isomerization:

\mathrm{NH_4(NCO) \rightarrow NH_3 + HNCO \leftrightarrow (NH_2)_2CO}

Complexation with oxalic acid helps drive this chemical equilibrium to completion.

The Wöhler synthesis is of great historical significance because for the first time an biological sources such as urine. Wöhler reported to his mentor Berzelius

"I cannot, so to say, hold my chemical water and must tell you that I can make urea without thereby needing to have kidneys, or anyhow, an animal, be it human or dog".

It is argued that organic chemistry did not actually start with this discovery in 1828 but 4 years earlier with the synthesis of carbon disulfide to acetic acid before vitalism started to lose supporters in serious numbers.


  1. ^  
  2. ^ Wöhler's Synthesis of Urea: How Do the Textbooks Report It? Paul S. Cohen, Stephen M. Cohen J. Chem. Educ. 1996 73 883 Abstract
  3. ^ A Demonstration of Wöhler's Experiment: Preparation of Urea from Ammonium Chloride and Potassium Cyanate Zoltán Tóth. J. Chem. Educ. 1996 73 539. Abstract
  4. ^ Recreation of Wöhler's Synthesis of Urea: An Undergraduate Organic Laboratory Exercise James D. Batchelor, Everett E. Carpenter, Grant N. Holder, Cassandra T. Eagle, Jon Fielder, Jared Cummings The Chemical Educator 1/Vol .3,NO.6 1998 ISSN 1430-4171 Online article
  • P. Walden (1928). "Die Bedeutung der Wöhlerschen Harnstoff-Synthese". Naturwissenschaften 16 (45–47): 835–849.  
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from Hawaii eBook Library are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.