Pedagogical Comparison of Five Reactions Performed under Microwave Heating in Multi-Mode versus Mono-Mode Ovens: Diels�Alder Cycloaddition, Wittig Salt Formation, E2 Dehydrohalogenation To Form an Alkyne, Williamson Ether Synthesis, and Fischer Esterification

• Autores: Marsha R. Baar, William Gammerdinger, Jennifer Leap, Erin Morales, Jonathan Shikora, Michael H. Weber
• Localización: Journal of chemical education, ISSN 0021-9584, Vol. 91, Nº 10, 2014, págs. 1720-1724
• Idioma: inglés
• Texto completo no disponible (Saber más ...)
• Resumen

  • Five reactions were rate-accelerated relative to the standard reflux workup in both multi-mode and mono-mode microwave ovens, and the results were compared to determine whether the sequential processing of a mono-mode unit could provide for better lab logistics and pedagogy. Conditions were optimized so that yields matched in both types of microwave ovens for a Diels-Alder cycloaddition, Wittig salt formation, Fischer esterifications, an E2 alkyne formation, and Williamson ether synthesis. Typically, a 10-fold rate acceleration was observed under mono-mode heating versus multi-mode heating, reducing the total run-time between 1.5 and 3.0 min per sample, which rivals the batch run-time of a multi-mode unit in ~16 student lab sections. Thus, the mono-mode microwave oven required a similar quantity of total reaction time in the lab, allowing students to run their experiments individually with less wait-time, competition for chemicals, equipment, and instrumentation and to complete the experiments in the lab period.