The Hammett Equation: Probing the Mechanism of Aromatic Semicarbazone Formation

• Glenn K. Ikeda ^[1] ; Karen Jang ^[1] ; Scott O. C. Mundle ^[1] ; Andrew P. Dicks ^[1]
  1. [1] University of Toronto

     University of Toronto

     Canadá

     
• Localización: Journal of chemical education, ISSN 0021-9584, Vol. 83, Nº 9, 2006, pág. 1341
• Idioma: inglés
• Texto completo no disponible (Saber más ...)
• Resumen

  • An organic class project is described where upper-level undergraduates measure kinetic rate constants for semicarbazone formation, by reacting semicarbazide with a meta- or para-substituted benzaldehyde. UV-vis spectroscopy is used to follow product formation. Individual results are compiled to yield a class data set, which is used to construct a linear Hammett plot applying empirical σX values. Students determine the reaction ρ value and use it to elucidate the rate-determining step of the multistep mechanism. An opportunity exists to interpret the form and meaning of a concave-downwards Hammett plot from the literature.