Vanishing Microwave Effects: Influence of Heterogeneity

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• 作者：Mark H. C. L. Dressen ; Bastiaan H. P. van de Kruijs ; Jan Meuldijk ; Jef A. J. M. Vekemans ; Lumbertus A. Hulshof
• 刊名：Organic Process Research & Development
• 出版年：2007
• 出版时间：September 2007
• 年：2007
• 卷：11
• 期：5
• 页码：865 - 869
• 全文大小：741K
• 年卷期：v.11,no.5(September 2007)
• ISSN：1520-586X

文摘

A consistent setup of experiments has been conducted to demonstrate an enhanced reaction rate under microwave irradiation as compared to conventional heating, i.e. a real microwave effect. It was found that addition of a cosolvent, diminishing the heterogeneous character of the reaction mixture, greatly reduced the microwave effect. This was demonstrated by two examples; selective mono-urea formation and racemization of an N-acetylamino acid. Furthermore, formation of a Grignard reagent was accelerated under MW irradiation by electrostatic etching of the metal surface. The microwave effect observed in these reactions seems to rely on heterogeneity and specific interactions on the solid–liquid interface. Basic understanding of these findings is crucial for scaling up microwave assisted processes.