The Isomerization of (-)-Menthone to (+)-Isomenthone Catalyzed by an Ion-Exchange Resin

• Autores: Aurora L. Ginzburg, Nicholas A. Baca, Philip D. Hampton
• Localización: Journal of chemical education, ISSN 0021-9584, Vol. 91, Nº 10, 2014, págs. 1748-1750
• Idioma: inglés
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• Resumen

  • A traditional organic chemistry laboratory experiment involves the acidcatalyzed isomerization of (-)-menthone to (+)-isomenthone. This experiment generates large quantities of organic and aqueous waste, and only allows the final ratio of isomers to be determined. A �green� modification has been developed that replaces the mineral acid catalyst with an acid-form ion-exchange resin, AMBERLYST 15DRY. This �green� modification dramatically reduces the quantity of waste, eliminates the hazards of concentrated acid, and allows for the isomer ratio to be monitored as a function of time.

    The pedagogical impact of the experiment has been significantly improved through examination of the effect of catalysis on the position of the equilibrium and on the kinetics of the reaction. As part of the experimental procedure, students generate their own hypothesis regarding the position of the equilibrium using molecular modeling of (-)-menthone and (+)-isomenthone. Students then test their hypothesis by performing the reaction with different catalyst quantities and at different temperatures. By pooling their data, students can examine the effect of both catalyst quantity and temperature on the position of the equilibrium, and the rate of the reaction.